masonry technical notes for design and construction

NCMA TEKNational Concrete Masonry Associationan information series from the national authority on concrete masonry technology

TEK 3-1BConstruction (2000)

ALL-WEATHER CONCRETEMASONRY CONSTRUCTION

INTRODUCTION

Masonry construction can continue during both hot andcold weather conditions. The ability to continue masonryconstruction in adverse weather conditions requires consid-eration of how environmental conditions may affect thequality of the finished masonry. In some cases, environmentalconditions may warrant the use of special construction proce-dures to ensure that the masonry work is not adverselyaffected.

One of the prerequisites of successful all-weather con-struction is advance knowledge of local conditions. Workstoppage may be justified if a short period of very cold or veryhot weather is anticipated. The best source for this type ofinformation is the U.S. Weather Bureau, EnvironmentalScience Services Administration (ESSA) of the U.S. Depart-ment of Commerce.

Although “normal”, “hot”, and “cold” are relative terms,building codes dictate when special construction proceduresare required. Typically, temperatures between 40 and 90oF(4.4 and 32.2oC) are considered “normal” temperatures formasonry construction.

In both hot and cold weather masonry construction, thegoverning requirements are based on the ambient tempera-ture during the construction phase and the mean daily tem-perature during the protection (curing) phase after construc-tion. The ambient temperature refers to the surroundingjobsite temperatures when the preparation activities andconstruction are in progress while the mean daily temperatureis the average of the hourly temperatures forecast by the localweather bureau over a 24 hour period.

COLD WEATHER CONSTRUCTION

Materials selected for normal temperature constructionwill generally require little change during construction in lowtemperature weather other than to insure that their tempera-ture is conducive to hydration of the cement.

Keywords: cold weather construction, construction tech-niques, grout, hot weather construction, mortar, rain, snow,storage of materials, wet weather construction

Mortar and Grout PerformanceHydration and strength development in mortar and grout

generally occurs at temperatures above 40oF (4.4oC) and onlywhen sufficient water is available. However, masonry con-struction may proceed when ambient temperatures are belowfreezing, provided the mortar or grout ingredients are heatedand the temperature of the freshly constructed masonry ismaintained above freezing during the initial hours afterconstruction.

Mortars and grouts mixed at low temperatures havelonger setting and hardening times, higher air contents, andlower early strength than those mixed at normal tempera-tures. Water requirements to provide a workable consistencymay be lower at cold temperatures. However, heated materialsproduce mortars and grouts with performance characteristicsidentical to those at the same temperature during warmweather.

Effects of FreezingThe water content of mortar is a significant factor

affecting mortar properties. When mortars with water con-tents in excess of 8% freeze, the resulting expansion has adisruptive effect on the cement-aggregate matrix of themortar (ref. 1). This disruptive effect increases as the watercontent increases. Therefore, mortar should not be allowed tofreeze until the mortar water content is reduced from theinitial 11% to 16% range to a value below 6%. Dry concretemasonry units have a demonstrated capacity to achieve thismoisture reduction in a relatively short time, commonlywithin 3 to 5 minutes (ref. 1).

Grout is a close relative of mortar in composition andperformance characteristics. During cold weather, however,special attention must be directed toward the protection ofgrout because of the higher water content and resultingdisruptive expansion that can occur from freezing of thatwater.

Like mortars, grouts undergo the hydration process, gainstrength, cool down, lose moisture to the adjacent masonryunits, and require protection through material heating orenclosures. Unlike mortars, grouts are confined within theenclosed cells of hollow concrete masonry units. To maintaingrout fluidity and mobility during placement, water contentmust be maintained at a very high level. These conditions

TEK 3-1B © 2000 National Concrete Masonry Association (replaces TEK 3-1A)

Table 1a—Cold Weather Masonry Construction Requirements (ref. 1, 3)

Ambienttemperature Construction requirements

25 to 40oF Do not lay masonry units having a temperature below 20oF (-6.7oC). Remove visible ice on (-3.9 to 4.4oC) or masonry units before the unit is laid in the masonry. Heat mixing water or sand to produce

masonry units below mortar and grout temperatures between 40 and 120oF (4.4 and 48.9oC). Maintain mortar40oF (4.4oC) above freezing until placement.

20 to 25oF Same as above, plus use heat sources on both sides of the masonry under construction and(-6.7 to -3.9oC) install wind breaks when wind velocity exceeds 15 mph (24.1 km/hr).

below 20oF (-6.7oC) Same as above, plus provide an enclosure for the masonry under construction and use heatsources to maintain temperatures above 32oF (0oC) within the enclosure.

not permitted to be used in mortar (ref. 3). The use of chlorideadmixtures is discouraged in grout.

There are several noncloride accelerators for mortar andgrout available that do not have the problems associated withchloride accelerators. While these accelerating admixturescan be of assistance in a cold weather environment projectthey must be used in addition to cold weather procedures andnot as a replacement for them.

Actual antifreezes, including several types of alcohol,are available. However, the bond strength of the masonry istypically reduced if used in quantities that will significantlylower the freezing point of mortar. Therefore, true antifreezesare not recommended.

Material StorageConstruction materials should be received, stored,

and protected in ways that prevent water from entering thematerials. Sand, when bulk delivered, should be coveredto prevent the entrance of water from rain or melted snow.Consideration should be given to methods of stockpilingthe sand that permit heating when low temperatures

make grouted masonry particularly vulnerable to detrimentalexpansion with early freezing. Therefore, grouted masonryneeds to be protected for longer periods to allow the watercontent to be dissipated.

CementDuring cold weather masonry construction, Type III,

high-early strength portland cement should be considered inlieu of Type I portland cement in mortar or grout to acceleratesetting. The acceleration not only reduces the curing time butgenerates more heat which is beneficial in cold weather.

AdmixturesThe purpose of an accelerating type of admixture is to

hasten the hydration of the portland cement in mortar orgrout. Calcium chloride is an ingredient in many proprietarycold weather admixtures. However, even small amounts ofcalcium chloride promote corrosion of metals embedded inor in contact with the masonry, can contribute to efflores-cence, and may cause masonry spalling. Accordingly, admix-tures containing chlorides in excess of 0.2% chloride ions are

Table 1b—Cold Weather Masonry Protection Requirements (ref. 1,3)

Mean dailytemperature Protection requirements

32 to 40oF Protect completed masonry from rain or snow by covering with a weather-resistive (0 to 4.4oC) membrane for 24 hours after construction.

25 to 32oF Completely cover the completed masonry with a weather-resistive membrane for 24 hours (-3.9 to 0oC) after construction.

20 to 25oF Completely cover the completed masonry with insulating blankets or equal protection for(-6.7 to -3.9oC) 24 hours after construction.

below 20oF (-6.7oC) Maintain masonry temperature above 32oF (0oC) for 24 hours after construction byenclosure with supplementary heat, by electric heating blankets, by infrared heat lamps,or by other acceptable methods.

Table 2a—Hot Weather Masonry Preparation and Construction Requirements (ref. 1, 3)

Ambienttemperature Preparation and construction requirements

Above 100oF (37.8oC) or Maintain sand piles in a damp, loose condition. Maintain temperature of mortar and grout above 90oF (32.2oC) below 120oF (48.9oC). Flush mixer, mortar transport container, and mortar boards with

with a wind > cool water before they come into contact with mortar ingredients or mortar. Maintain8 mph (12.9 km/hr) mortar consistency by retempering with cool water. Use mortar within 2 hours of initial

mixing.

Above 115oF (46.1oC) or Same as above, plus materials and mixing equipment are to be shaded from direct sunlight.above 105oF (40.6oC) Use cool mixing water for mortar and grout. Ice is permitted in the mixing water as long as

with a wind > it is melted when added to the other mortar or grout materials.8 mph (12.9 km/hr)

Table 2b—Hot Weather Masonry Protection Requirements (ref. 1,3)

Mean dailytemperature Protection requirements

Above 100oF (37.8oC) or Fog spray all newly constructed masonry until damp, at least three times a day until the above 90oF (32.2oC) masonry is three days old.

with a wind >8 mph (12.9 km/hr)

warrant. Bagged materials and masonry units should beprotected from precipitation and ground water by storageon pallets or other acceptable means.

Coverings for materials include tarpaulins, reinforcedpaper, polyethylene, or other water repellent sheet mate-rials. If the weather and size of the project warrant, ashelter may be provided for the material storage andmortar mixing areas.

Material HeatingIf climatic conditions warrant, temperatures of construc-

tion materials should be measured. This can be accomplishedusing a metal tip immersion thermometer for materials,mortar, and grout. The temperature of masonry units can bemeasured using a metallic surface contact thermometer.

Although the Specifications for Masonry Structures(ref. 3) allows heating of either the mixing water or the sandto increase the temperature of mortar or grout, the mostconvenient method of increasing the temperature during coldweather is to heat the mixing water. Material temperaturerequirements for cold weather construction are given in Table1a.

As indicated in Table 1a, the temperature of drymasonry units may be as low as 20oF (-6.7oC) at the timeof placement (ref. 3). However, wet frozen masonry unitsshould be thawed before placement in the masonry. Also,even when the temperature of dry units approach the 20oF(-6.7oC) threshold, it may be advantageous to heat theunits for greater mason productivity.

Masonry should never be placed on a snow or ice-covered surface. Movement occurring when the base thawswill cause cracks in the masonry. Furthermore, the bondbetween the mortar and the supporting surface will be com-promised.

Protection and Wind BreaksAn enclosed construction site maintained at a tempera-

ture greater than 40oF (4.4oC) would be ideal for all coldweather construction. Specific minimum levels of protectionand wind breaks are outlined in Tables 1a and 1b. Materialscommonly used for protection are canvas and syntheticcoverings (reinforced polyethylene and vinyl).

Glass Unit MasonryFor glass unit masonry, both the ambient temperature and theunit temperature must be above 40oF (4.4oC) and maintainedabove that temperature for the first 48 hours (ref. 3).

HOT WEATHER CONSTRUCTION

High temperatures, solar radiation, and ambient relativehumidity influence the absorption characteristics of the ma-sonry units and the setting time and drying rate for mortar.When mortar gets too hot, it may lose water so rapidly that thecement does not fully hydrate. Early surface drying of themortar results in decreased bond strength and less durablemortar. Hot weather construction procedures involve keepingmasonry materials as cool as possible and preventing exces-

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REFERENCES1. Hot & Cold Weather Masonry Construction. Masonry Industry Council, 1999.2. Drysdale, Robert G., Ahmad A. Hamid, and Lawrie R. Baker, Masonry Structures Behavior and Design, Second Edition.

The Masonry Society, 1999.3. Specifications for Masonry Structures, ACI 530.1-99/ASCE 6-99/TMS 602-99. Reported by the Masonry Standards Joint

Committee, 1999.

sive water loss from the mortar. Specific hot weather require-ments of the Specifications for Masonry Structures (ref. 3)are shown in Tables 2a and 2b.

Additional RecommendationsMasonry materials stored in the sun can become hot

enough to impact mortar temperatures. It is helpful ifmaterials can be stored in a shaded area. Dark coloredmaterials will heat up faster than lighter colored materials,and may require more protection from unwanted heat gain.By the same token, water hoses exposed to direct sunlight canresult in water with highly elevated temperatures. To allevi-ate this, a water barrel should be used. The barrel may be filledwith water from a hose, but the hot water resulting from hoseinactivity should be flushed and discarded first. Additionally,mortar mixing times should be no longer than 3 to 5 minutessince long mix times can accelerate the mortar setting time.Mixing smaller batches of mortar also will help minimizedrying time on the mortar boards.

To minimize mortar surface drying, past requirementsof Specifications for Masonry Structures (ref. 3) were to notspread mortar bed joints more than 4 feet (1.2 m) ahead ofmasonry and to set masonry units within one minute of

spreading mortar. This is no longer a requirement in thecurrent document but the concept still merits consideration.Actual distance and time varies according to the site condi-tions and should be determined on an individual basis. Ifsurface drying does occur, the mortar can often be revitalizedby wetting the wall to reintroduce water to complete thehydration process. If a fog spray nozzle is not available, careshould be taken to avoid washout of fresh mortar joints whenusing a higher pressure water spray.

WET WEATHER CONSTRUCTION

Masonry construction should not continue during rain. Whenrain is likely, all materials including sand and units both onthe ground and on the scaffold should be covered. Newlyconstructed walls should be protected by draping a weather-resistant covering over the wall and extending it below mortarthat is still susceptible to washout. Partially set mortar duringheavy downpours can be susceptible to washout of some of thecementitious components resulting in reduced strength andpossible staining of the wall. However, after about 24 hoursof hardening, wetting by rain provides additional beneficialcuring of the masonry (ref. 2).

TEK 3-8A © 2001 National Concrete Masonry Association (replaces TEK 3-8)


CONCRETE MASONRY CONSTRUCTION TEK 3-8AConstruction (2001)

Keywords: ASTM specifications, bond patterns, cleaning,construction techniques, construction tolerances, grout, mortar.

INTRODUCTIONConcrete masonry is a popular building material because

of its strength, durability, economy, and its resistance to fire,noise, and insects. To function as designed however, concretemasonry buildings must be constructed properly.

This TEK provides a brief overview of the variety ofmaterials and construction methods currently applicable toconcrete masonry. In addition, a typical construction sequenceis described in detail.

MATERIALS

The constituent masonry materials: concrete block, mor-tar, grout, and steel, each contribute to the performance of amasonry structure. Concrete masonry units provide strength,durability, fire resistance, energy efficiency, and sound attenu-ation to a wall system. In addition, concrete masonry units aremanufactured in a wide vari-ety of sizes, shapes, colors,and architectural finishes toachieve any number of ap-pearances and functions. TheConcrete Masonry Shapesand Sizes Manual (ref. 4)illustrates a broad samplingof available units.

While mortar consti-tutes approximately 7% of atypical masonry wall area, itsinfluence on the performanceof a wall is significant. Mor-tar bonds the individual ma-sonry units together, allow-ing them to act as a compos-ite structural assembly. Inaddition, mortar seals jointsagainst moisture and air leak-age and bonds to joint rein-forcement, anchors, and tiesto help ensure all elements

perform as a unit.Grout is used to fill masonry cores or wall cavities to

improve the structural performance and/or fire resistance ofmasonry. Grout is most commonly used in reinforced con-struction, to structurally bond the steel reinforcing bars to themasonry, allowing the two elements to act as one unit inresisting loads.

Reinforcement incorporated into concrete masonry struc-tures increases strength and ductility, providing increased re-sistance to applied loads and, in the case of horizontal rein-forcement, to shrinkage cracking.

Specifications governing material requirements are listedin Table 1.

CONSTRUCTION METHODS

Mortared ConstructionMost concrete masonry construction is mortared con-

struction, i.e., units are bonded together with mortar. Varyingthe bond or joint pattern of a concrete masonry wall can createa wide variety of interesting and attractive appearances. In

Placement of Concrete Masonry Units

Table 1—Masonry Material Specifications

UnitsLoadbearing Concrete Masonry Units, ASTM C 90Concrete Building Brick, ASTM C 55Calcium Silicate Face Brick (Sand-Lime Brick), ASTM C 73Nonloadbearing Concrete Masonry Units, ASTM C 129Prefaced Concrete and Calcium Silicate Masonry

Units, ASTM C 744

MortarMortar for Unit Masonry, ASTM C 270

GroutGrout for Masonry, ASTM C 476

ReinforcementAxle-Steel Deformed and Plain Bars for Concrete

Reinforcement, ASTM A 617Deformed and Plain Billet-Steel Bars for Concrete

Reinforcement, ASTM A 615Epoxy-Coated Reinforcing Steel Bars, ASTM A 775Low-Alloy Steel Deformed Bars for Concrete

Reinforcement, ASTM A 706Rail-Steel Deformed and Plain Bars for Concrete

Reinforcement, ASTM A 616Zinc-Coated (Galvanized) Steel Bars for Concrete

Reinforcement, ASTM A 767Masonry Joint Reinforcement, ASTM A 951

Ties & AnchorsSteel Wire, Plain, for Concrete Reinforcement, ASTM A 82Stainless and Heat-Resisting Steel Wire, ASTM A 580

contains further information on this method of construction.

CONSTRUCTION SEQUENCE

Mixing MortarTo achieve consistent mortar from batch to batch, the same

quantities of materials should be added to the mixer, and theyshould be added in the same order. Mortar mixing times,placement methods, and tooling must also be consistent toachieve uniform mortar for the entire job.

In concrete masonry construction, site-mixing of mortarshould ideally be performed in a mechanical mixer to ensureproper uniformity throughout the batch. Mortar materialsshould be placed in the mixer in a similar manner from batchto batch to maintain consistent mortar properties. Typically,about half the mixing water is added first into a mixer. Ap-proximately half the sand is then added, followed by any lime.The cement and the remainder of the sand are then added. Asthe mortar is mixed and begins to stiffen, the rest of the wateris added. Specification for Masonry Structures (ref. 7) re-quires that these materials be mixed for 3 to 5 minutes. If themortar is not mixed long enough, the mortar mixture may notattain the uniformity necessary for the desired performance. Alonger mixing time can increase workability, water retention,and board life.

The mortar should stick to the trowel when it is picked up,and slide off the trowel easily as it is spread. Mortar shouldalso hold enough water so that the mortar on the board will notlose workability too quickly, and to allow the mason to spreadmortar bed joints ahead of the masonry construction. The mor-tar must also be stiff enough to initially support the weight ofthe concrete masonry units.

To help keep mortar moist, the mortarboard should bemoistened when a fresh batch is loaded. When mortar on theboard does start to dry out due to evaporation, it should beretempered. To retemper, the mortar is mixed with a smallamount of additional water to improve the workability. After asignificant amount of the cement has hydrated, retemperingwill no longer be effective. For this reason, mortar can beretempered for only 11/2

to 21/2

hours after initial mixing,

depending on the site conditions. For example, dry, hot, andwindy conditions will shorten the board life, and damp, cool,calm conditions will increase the board life of the mortar. Mor-tar should be discarded if it shows signs of hardening or if 21/2

hours have passed since the original mixing.

Placing MortarHead and bed joints are typically 3/8 in. (10 mm) thick, except atfoundations. Mortar should extend fully across bedding sur-faces of hollow units for the thickness of the face shell, so thatjoints will be completely filled. Solid units are required to befully bedded in mortar.

Although it is important to provide sufficient mortar toproperly bed concrete masonry units, excessive mortar shouldnot extend into drainage cavities or into cores to be grouted.For grouted masonry, mortar protrusions extending more than1/2 in. (13 mm) into cells or cavities to be grouted should beremoved (ref. 7).

addition, the strength of the masonry can be influenced by thebond pattern. The most traditional bond pattern for concretemasonry is running bond, where vertical head joints are offsetby half the unit length.

Excluding running bond construction, the most popularbond pattern with concrete masonry units is stack bond. Al-though stack bond typically refers to masonry constructed sothat the head joints are vertically aligned, it is defined asmasonry laid such that the head joints in successive courses arehorizontally offset less than one quarter the unit length (ref. 2).Concrete Masonry Bond Patterns (ref. 3) shows a variety ofbond patterns and describes their characteristics.

Dry-Stacked ConstructionThe alternative to mortared construction is dry-stacked

(also called surface bonded) construction, where units areplaced without any mortar, then both surfaces of the wall arecoated with surface bonding material. Shims or ground units areused to maintain elevations. This construction method results infaster construction, and is less dependent on the skill of thelaborer than mortared construction. In addition, the surfacebonding coating provides excellent rain penetration resistance.Surface Bonded Concrete Masonry Construction (ref. 9)

The Importance of Laying to the LineExperienced masons state that they can lay about five times

as many masonry units when working to a mason line than whenusing just their straightedge. The mason line gives the mason aguide to lay the block straight, plumb, at the right height, andlevel. The line is attached so that it gives a guide in aligning thetop of the course.

If a long course is to be laid, a trig may be placed at one ormore points along the line to keep the line from sagging. Be-fore work begins, the mason should check to see that the lineis level, tight, and will not pull out.

Each mason working to the same line needs to be carefulnot to lay a unit so it touches the line. This will throw the lineoff slightly and cause the rest of the course to be laid out ofalignment. The line should be checked from time to time to becertain it has remained in position.

PLACING UNITS

The FoundationBefore building the block wall, the foundation must be

level, and clean so that mortar will properly adhere. It mustalso be reasonably level. The foundation should be free of ice,dirt, oil, mud, and other substances that would reduce bond.

Laying Out the WallTaking measurements from the foundation or floor plan

and transferring those measurements to the foundation, foot-ing, or floor slab is the first step in laying out the wall.

Once two points of a measurement are established, cor-ner to corner, a chalk line is marked on the surface of the foun-dation to establish the line to which the face of the block willbe laid. Since a chalk line can be washed away by rain, a greasecrayon, line paint, nail or screwdriver can mark the surface forkey points along the chalk line, and a chalk line re-snapped alongthese key points. After the entire surface is marked for loca-tions of walls, openings, and control joints, a final check of allmeasurements should be made.

The Dry Run—Stringing Out The First CourseStarting with the corners, the mason lays the first course

without any mortar so a visual check can be made between thedimensions on the floor or foundation plan and how the firstcourse actually fits the plan. During this dry layout, concreteblocks will be strung along the entire width and length of thefoundation, floor slab, and even across openings. This will showthe mason how bond will be maintained above the opening. Itis helpful to have 3/8 in. (10 mm) wide pieces of wood to placebetween block as they are laid dry, to simulate the mortar joints.

At this dry run the mason can check how the block willspace for openings which are above the first course—windows,etc., by taking away block from the first course and checkingthe spacing for the block at the higher level. These checks willshow whether or not units will need to be cut. Window anddoor openings should be double checked with the window shopdrawings prior to construction.

When this is done, the mason marks the exact location

and angle of the corners. It is essential that the corner be builtas shown on the foundation or floor plan, to maintain modulardimensions.

Laying the Corner UnitsBuilding the corners is the most precise job facing the

mason as corners will guide the construction of the rest of thewall. A corner pole can make this job easier. A corner pole isany type of post which can be braced into a true vertical posi-tion and which will hold a taut mason’s line without bending.Corner poles for concrete block walls should be marked every4 or 8 in. (102 to 203 mm), depending on the course height,and the marks on both poles must be aligned such that themason’s line is level between them.

Once the corner poles are properly aligned, the first courseof masonry is laid in mortar. Typically, a mortar joint between1/4 and 3/4 in. (6.4 to 19 mm) is needed to make up for irregu-larities of the footing surface. The initial bed joint should be afull bed joint on the foundation, footing, or slab. In some ar-eas, it is common practice to wet set the initial course of ma-sonry directly in the still damp concrete foundation.

Where reinforcing bars are projecting from the founda-tion footing or slab, the first course is not laid in a full mortarbed. In this case, the mason leaves a space around the rein-forcing bars so that the block will be seated in mortar but themortar will not cover the area adjacent to the dowels. This per-mits the grout to bond directly to the foundation in these loca-tions.

After spreading the mortar on the marked foundation, thefirst block of the corner is carefully positioned. It is essentialthat this first course be plumb and level.

Once the corner block is in place, the lead blocks are set—three or four blocks leading out from each side of the corner.The head joints are buttered in advance and each block is lightlyshoved against the block in place. This shove will help make atighter fit of the head joint, but should not be so strong as tomove the block already in place. Care should be taken to spreadmortar for the full height of the head joint so voids and gaps donot occur.

If the mason is not working with a corner pole, the firstcourse leads are checked for level, plumb, and alignment witha level.

Corners and leads are usually built to scaffold height, witheach course being stepped back one half block from the coursebelow. The second course will be laid in either a full mortarbed or with face shell bedding, as specified.

Laying the WallEach course between the corners can now be laid easily

by stretching a line between. It should be noted that a block hasthicker webs and face shells on top than it has on the bottom.The thicker part of the webs should be laid facing up. This pro-vides a hand hold for the mason and more surface area for mor-tar to be spread. The first course of block is thereafter laidfrom corner to corner, allowing for openings, with a closureblock to complete the course. It is important that the mortarfor the closure block be spread so all edges of the openingbetween blocks and all edges of the closure block are buttered

before the closure block is carefully set in place. Also, thelocation of the closure block should be varied from course tocourse so as not to build a weak spot into the wall.

The units are leveled and plumbed while the mortar is stillsoft and pliable, to prevent a loss of mortar bond if the unitsneed to be adjusted.

As each block is put in place, the mortar which is squeezedout should be cut off with the edge of the trowel and care shouldbe taken that the mortar doesn’t fall off the trowel onto thewall or smear the block as it is being taken off. Should somemortar get on the wall, it is best to let it dry before taking it off.

All squeezed out mortar which is cut from the mortar jointscan either be thrown back onto the mortar board or used tobutter the head joints of block in place. Mortar which has fallenonto the ground or scaffold should never be reused.

At this point, the mason should:• Use a straightedge to assure the wall is level, plumb and

aligned.• Be sure all mortar joints are cut flush with the wall, await-

ing tooling, if necessary.• Check the bond pattern to ensure it is correct and that

the spacing of the head joints is right. For running bond,this is done by placing the straightedge diagonally acrossthe wall. If the spacing of head joints is correct, all theedges of the block will be touched by the straightedge.

• Check to see that there are no pinholes or gaps in themortar joints. If there are, and if the mortar has not yettaken its first set, these mortar joint defects should berepaired with fresh mortar. If the mortar has set, the onlyway they can be repaired is to dig out the mortar jointwhere it needs repairing, and tuckpoint fresh mortar inits place.

Tooling JointsWhen the mortar is thumbprint hard, the head joints are

tooled, then the horizontal joints are finished with a sled run-ner and any burrs which develop are flicked off with the bladeof the trowel. When finishing joints, it is important to pressfirmly, without digging into the joints. This compresses thesurface of the joint, increasing water resistance, and also pro-motes bond between the mortar and the block. Unless other-wise required, joints should be tooled with a rounded jointer,producing a concave joint. Once the joints are tooled, the wallis ready for cleaning.

CleanupMasonry surfaces should be cleaned of imperfections that

may detract from the final appearance of the masonry structureincluding stains, efflorescence, mortar droppings, grout drop-pings, and general debris.

Cleaning is most effective when performed during the wallconstruction. Procedures such as skillfully cutting off excessmortar and brushing the wall clean before scaffolding is raised,help reduce the amount of cleaning required.

When mortar does fall on the block surface, it can oftenbe removed more effectively by letting it dry and then knock-ing it off the surface. If there is some staining on the face ofthe block, it can be rubbed off with a piece of broken block, or

brushed off with a stiff brush.Masons will sometimes purposefully not spend extra

time to keep the surface of the masonry clean during con-struction because more aggressive cleaning methods mayhave been specified once the wall is completed. This is of-ten the case for grouted masonry construction where groutsmears can be common and overall cleaning may be neces-sary.

The method of cleaning should be chosen carefully asaggressive cleaning methods may alter the appearance ofthe masonry. The method of cleaning can be tested on thesample panel or in an inconspicuous location to verify thatit is acceptable.

Specification for Masonry Structures (ref. 7) statesthat all uncompleted masonry work should be covered atthe top for protection from the weather.

DIMENSIONAL TOLERANCES

While maintaining tight construction tolerances is de-sirable to the appearance, and potentially to the structuralintegrity of a building, it must be recognized that factorssuch as the condition of previous construction and non-modularity of the project may require the mason to vary themasonry construction slightly from the intended plans orspecifications. An example of this is when a mason mustvary head or bed joint thicknesses to fit within a frame orother preexisting construction. The ease and flexibility withwhich masonry construction accommodates such change isone advantage to using masonry. However, masonry shouldstill be constructed within certain tolerances to ensure thestrength and appearance of the masonry is not compromised.

Specification for Masonry Structures (ref. 7) containssite tolerances for masonry construction which allow fordeviations in the construction that do not significantly alterthe structural integrity of the structure. Tighter tolerancesmay be required by the project documents to ensure the fi-nal overall appearance of the masonry is acceptable. If sitetolerances are not being met or cannot be met due to previ-ous construction, the Architect/Engineer should be notified.

Mortar Joint TolerancesMortar joint tolerances are illustrated in Figure 1. Al-

though bed joints should be constructed level, they are per-mitted to vary by ± 1/2 in. (13 mm) maximum from levelprovided the joint does not slope more than ± 1/4 in. (6.4mm) in 10 ft (3.1 m).

Collar joints, grout spaces, and cavity widths are per-mitted to vary by -1/4 in. to + 3/8 in. (6.4 to 9.5 mm). Provi-sions for cavity width are for the space between wythes ofnon-composite masonry. The provisions do not apply to situ-ations where the masonry extends past floor slabs or span-drel beams.

Dimensions of Masonry ElementsFigure 2 shows tolerances that apply to walls, columns,

and other masonry building elements. It is important to notethat the specified dimensions of concrete masonry units are

Figure 1—Mortar Joint Tolerances

Figure 2—Element Cross Section and ElevationTolerances

Figure 3—Permissible Variations From Plumb

Figure 4—Location Tolerances in Plan

3/8 in. (9.5 mm) less than the nominal dimensions. Thus awall specified to be constructed of 8 in. (203 mm) concretemasonry units should not be rejected because it is 7 5/8 in. (194mm) thick, less than the apparent minimum of 7 3/4 in. (197mm) (8 in. (203 mm) minus the 1/4 in. (6.4 mm) tolerance).Instead the tolerance should be applied to the 7 5/8 in. (194mm) specified dimension.

Plumb, Alignment, and Levelness of Masonry ElementsTolerances for plumbness of masonry walls, columns,

and other building elements are shown in Figure 3. Masonrybuilding elements should also maintain true to a line withinthe same tolerances as variations from plumb.

Columns and walls continuing from one story to an-other may vary in alignment by ± 3/4 in. (19 mm) fornonloadbearing walls or columns and by ± 1/2 in. (13 mm)for bearing walls or columns.

The top surface of bearing walls should remain levelwithin a slope of ± 1/4 in. (6.4 mm) in 10 ft (3.1 m), but nomore than ± 1/2 in. (13 mm).

Location of ElementsRequirements for location of elements are shown in Fig-

ures 4 and 5.

Figure 5—Location Tolerances in Story Height

NATIONAL CONCRETE MASONRY ASSOCIATION To order a complete TEK Manual or TEK Index,2302 Horse Pen Road, Herndon, Virginia 20171-3499 contact NCMA Publications (703) 713-1900www.ncma.org

REFERENCES1. Building Block Walls, VO 6. National Concrete Masonry Association, 1988.2. Building Code Requirements for Masonry Structures, ACI 530-99/ASCE 5-99/TMS 402-99. Reported by the Masonry

Standards Joint Committee, 1999.3. Concrete Masonry Bond Patterns, TEK 14-6. National Concrete Masonry Association, 1999.4. Concrete Masonry Shapes and Sizes Manual, CM 260A. National Concrete Masonry Association, 1997.5. Inspection of Concrete Masonry Construction, TR 156. National Concrete Masonry Association, 1996.6. Nolan, K. J. Masonry & Concrete Construction. Craftsman Book Company, 1982.7. Specification for Masonry Structures, ACI 530.1-99/ASCE 6-99/TMS 602-99. Reported by the Masonry Standards Joint

Committee, 1999.8. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90-00. American Society for Testing and

Materials, 2000.9. Surface Bonded Concrete Masonry Construction, TEK 3-5A. National Concrete Masonry Association, 1998.

TEK REVIEW AND COMMENT REQUESTED

\\KITCHEN\SharedDocs\TEK-rvw.doc

Date: March 19, 2003

TEK 3-7A CM Fireplaces TEK is an educational series directed to designers, contractors, producers and consumers. The series is intended to reflect state-of-the-art technology in accordance with a consensus of experts. To help ensure this consensus, your review and comment is needed. Your comments, along with those from other reviewers, will be the basis for revisions. Your assistance in maintaining this resource is greatly appreciated. Return comments by: Wednesday, March 26 2003 To help your review, the following highlights items updated from the previous version of this TEK:

• Fireplace requirements were updated to the 2000 IRC Please return comments to Maribeth Bradfield via e-mail ([email protected]) by fax (703-524-4277) or phone (703-599-8234). Comments: q See Attached q Reviewed/No comments q Not reviewed Specific Comments:

NCMA Staff: ¨ R. L. Carter ¨ C. Clark ¨ L. Dunne ¨ D. W. Graber ¨ J. H. Greenwald ¨ J. R. Harke ¨ M. B. Hogan ¨ H. W. Junk ¨ B. R. KamHong ¨ R. D. Thomas ¨ J. J. Thompson

State Alliance Reps: ¨ Gene Abbate ¨ Robert Bertazon ¨ Joan Borter ¨ Jan Boyer ¨ James Darcy ¨ David Dimmick ¨ Aleta Fairbanks ¨ Ben Fry ¨ Mike Johnsrud ¨ Wayne Kawano ¨ Roy Keck ¨ Paul LaVene ¨ Chris Lechner ¨ Donald D. Littler ¨ Andrew Mackie ¨ Robert Melton ¨ Linda S. Muller ¨ Josh Naragon ¨ Charles Ostrander ¨ Jeff Patterson ¨ Otis Russell ¨ David Sethre ¨ Robert Sitter ¨ Mark Smith ¨ Jack Stubbs ¨ Ann Sullivan ¨ Robert Varner ¨ Linda Warden ¨ Richard Walter ¨ Tom Young

Other Reviewers: ¨ Don Beers ¨ Bruce Clark ¨ Allan Gow ¨ Jim Gulde ¨ Doug Jeffords ¨ Tim Mallis ¨ John Melander ¨ James McKinney ¨ W. David Miller ¨ Greg Page ¨ Don Sheffield ¨ Jeff Speck ¨ Ken Sroka ¨ Billy Wehunt ¨ Frank Werner ¨ Mark Wilhelms ¨ Daniel Zechmeister ¨ Rob Zobel

D RA F T



CONCRETE MASONRY FIREPLACES TEK 3-7AConstruction (2003)

Keywords: chimneys, construction details, corbels,fireplaces, fire protection, footings

INTRODUCTION

The fireplace is an American traditionand remains today a central feature of thehome. Concrete masonry, due to its inherentfire resistance and beauty, is a popular andversatile building material for fireplace con-struction.

Noncombustible concrete masonry ef-fectively isolates the fireplace fire fromnearby combustible materials such as wood,plastic and insulation. In addition, becauseof concrete masonry's thermal mass, heat isstored in the concrete masonry itself. Thus,heat is not only radiated to the room fromthe fire, but also from the concrete masonryhours after the fire dies.

Concrete masonry fireplaces are a safeand efficient source of auxiliary heat whenproperly designed and constructed. Allfireplaces contain essentially the same ele-ments: a base, combustion chamber, smokechamber and chimney, as shown in Figure 1for a single opening fireplace. Require-ments herein are based on the 2000 Interna-tional Residential Code (IRC) (ref. 1).

BASE

The fireplace base consists of the foun-dation and hearth extension support. Thefoundation consists of a concrete footingand concrete masonry foundation walls or athickened slab for slab-on-grade construc-tion (see Figure 1). Void areas are oftenprovided in the base to form an air passagefor external combustion air, an ash pit orboth. Nonessential void areas should besolidly filled with masonry.

Immediately above the foundation

walls, support for the combustion chamber and the hearthextension are necessary. The hearth extension may be sup-ported by corbelling the masonry foundation wall, but isusually provided by a poured concrete slab that also supportsthe combustion chamber. Forming the concrete slab requires“block outs” for external combustion air dampers and ash

Figure 1—Single Opening Fireplace

Concrete footing

Cleanout door

Temporary forming

Concrete slab

Double joists

Hearth extension, 2 in. (51 mm) min. thickness

Fireplace opening height

External airdamper

Hearth, 4in. (102 mm) min. thickness

Lintel angle

8 in. (203 mm), min.

Mantle

Chimney block or concrete brick Fire clay

flue liner

Chimney

Smoke chamber, height ≤ inside

width of fireplace opening

Flue liner support

Parging

Combustion chamber

Noncombustible material

Smoke shelf

Throat damper

Smoke dome

Flue

Ash dump

Base assembly

8 in. (203 mm), min.

External air supply register

Non-combustible forming

6 in. (152 mm), min.

12 in. (305 mm), min.

Air passageway

Ash drop

Air space

Parging

20 in. (508 mm) min.

D R A F T

drops if there are air passageways or ash pits incorporated intothe base of the fireplace. If permanent forming is required atthe top of the foundation walls, it must be a noncombustiblematerial. Temporary wood forming is typically used to pourthe hearth extension support. The forming should be placedso that the projected slab will meet a doubled wood floor joist,and be such that it can be easily removed.

The concrete slab should be 4 in. (102 mm) thick,reinforced and capable of resisting thermal stresses resultingfrom high temperatures.

The hearth extension must extend at least 16 in. (406 mm)in front of the fireplace face and at least 8 in. (203 mm) beyondeach side of the fireplace opening for fireplaces with openingsthat are less than 6 ft 2 (0.56 m2). If the area of the fireplaceopening is 6 ft2 (0.56 m2) or larger, the hearth extension mustbe 20 in. (508 mm) in front of the fireplace face and at least12 in. (305 mm) beyond each side of the opening. Because thehearth extension must be constructed of noncombustiblematerials, concrete brick or decorative concrete masonryunits are often used to construct the hearth extension.

COMBUSTION CHAMBER

The combustion chamber consists of the hearth exten-sion, the firebox and surrounding masonry and the throat.

Fire brick, if used, must a conform to StandardClassification of Fireclay and High-Alumina Re-fractory Brick , ASTM C 27 or Standard Specifica-tion for Firebox Brick for Residential Fireplaces, C1261 (refs. 2, 3), laid to form a firebox wall thick-ness of at least 2 in. (51 mm). Fire brick is laid usingmedium-duty refractory mortar conforming to Stan-dard Test Method for Pier Test for RefractoryMortars, ASTM C 199 (ref. 4), with mortar jointsno larger than 1/4 in. (6.35 mm). The total minimumthickness of the back and side walls must be 8 in. (203mm) of solid masonry including the lining. When no

lining is used, this minimum thickness is 10 in. (254 mm).The fireplace opening should be based on the room size

for aesthetics and also to prevent overheating the room.Suggested fireplace opening widths are provided in Table 1.Once the opening width is selected, the dimensions of themasonry combustion chamber may be determined using Table 2.

The steel angle lintel used above the fireplace openingshould not be solidly embedded in mortar. With the ends freeto move, lintel expansion due to high temperatures will notcrack the masonry. The use of noncombustible fibrous insu-lation at the ends of the lintel angle will usually compensatefor this expansion and eliminate cracking problems.

The size and position of the throat is critical for properburning and draft. The fireplace throat should be as wide asthe firebox and should be not less than 8 in. (203 mm) abovethe fireplace opening.

SMOKE CHAMBER

The smoke chamber consists of the damper, smoke shelf,smoke dome and surrounding concrete masonry. The damper,which is critical for proper performance, is placed directlyover the throat. The metal damper, like the lintel over thefireplace opening, should not be solidly embedded in mortar.When the fireplace is not in use, the damper should be closed

Table 1—Suggested Width of Fireplace Openings Appropriateto Size of Room (ref. 5)

Size of room, Width of fireplace opening, in. (mm)ft x ft (m x m) in short wall in long wall

10 x 14 (3.05 x 4.27) 24 (610) 24 to 32 (610-813)12 x 16 (3.66 x 4.88) 28 to 36 (711-914) 32 to 36 (813-914)12 x 20 (3.66 x 6.10) 32 to 36 (813-914) 36 to 40 (914-1,016)12 x 24 (3.66 x 7.32) 32 to 36 (813-914) 36 to 48 (914-1,219)14 x 28 (4.27 x 8.53) 32 to 40 (813-1,016) 40 to 48 (1,016-1,219)16 x 30 (4.88 x 9.14) 36 to 40 (914-1,016) 48 to 60 (1,219-1,524)20 x 36 (6.10 x 10.97) 40 to 48 (1,016-1,219) 48 to 72 (1,219-1,829)

Table 2—Single-Opening Fireplace Dimensions, Inches (ref. 5)a

Opening Firebox Throat Smoke chamber Steel anglesRear wall depth

Width Height Depth Width Vertical Splayed Width Height Shelf Length Sizeheight height depth

24 24 16 11 14 18 83/432 19 12 36 3 x 3 x 1/4

26 24 16 13 14 18 83/434 21 12 36 3 x 3 x 1/4

28 24 16 15 14 18 83/436 21 12 36 3 x 3 x 1/4

30 29 16 17 14 23 83/438 24 12 42 3 x 3 x 1/4

32 29 16 19 14 23 83/440 24 12 42 3 x 3 x 1/4

36 29 16 23 14 23 83/444 27 12 48 3 x 3 x 1/4

40 29 16 27 14 23 83/448 29 12 48 3 x 3 x 1/4

42 32 16 29 16 24 83/450 32 12 54 31/2 x 3 x 1/4

48 32 18 33 16 24 83/456 37 14 60 31/2 x 3 x 1/4

54 37 20 37 16 29 13 68 45 12 66 31/2 x 3 x 1/460 37 22 42 16 29 13 72 45 14 72 31/2 x 3 x 1/460 40 22 42 18 30 13 72 45 14 72 5 x 31/2 x 5/1672 40 22 54 18 30 13 84 56 14 84 5 x 31/2 x 5/16

a For millimeters, multiply inches by 25.4.

D R A F T

to prevent heat loss. When a fire is started, the damper shouldbe wide open. Once the fire is burning readily, the dampershould be adjusted to produce more efficient combustion.Keeping the damper wide open reduces the fireplace effi-ciency. For convenience and safety, a rotary controlled damperthat is adjusted with a control on the face of the fireplace ispreferred, since adjusting a poker controlled damper usuallyrequires reaching into the firebox.

The masonry above the damper should be supported ona second lintel angle rather than bearing on the damper. Thislintel angle must be allowed to expand independently from themasonry and thus should not be solidly embedded in themasonry.

Immediately behind the damper is the smoke shelf, whichchecks down drafts. Any down drafts strike the smoke shelfand are diverted upward by the damper assembly. The smokeshelf may be curved to assist in checking down drafts, but flatsmoke shelves perform adequately.

The smoke dome should be constructed so that the sidewalls and front wall taper inward to form the chimney support.The walls of the smoke dome should be solid masonry orhollow unit masonry grouted solid and should provide aminimum of 8 in. (203 mm) of solid masonry between thesmoke dome and exterior surfaces when no lining is used.When the smoke dome is lined using fire brick at least 2 in. (51mm) thick or vitrified clay at least 5/8 in. (16 mm) thick, thisminimum thickness is reduced to 6 in. (152 mm). The insideof the smoke dome should be parged to reduce friction andhelp prevent gas and smoke leakage (when the inside isformed by corbelling the masonry, this parging is required).

For ease of construction, a high form damper may beused. High form dampers are constructed such that the damper,smoke shelf and smoke dome are contained in one metal unit.In addition, fireplace inserts may be used. Inserts include theelements of the high form damper as well as the firebox. Theinserts are placed directly on the firebrick hearth.

FLUE AND CHIMNEY

The chimney should be positioned so that it is centered onthe width of the fireplace and the back of the flue liner alignswith the vertical rear surface of the smoke dome. This con-figuration funnels the smoke and gases from the fire into thechimney. The chimney is constructed directly on the smokechamber and consists of a flue liner and a chimney wall. Forresidential fireplaces, the flue lining may be a clay flue liningcomplying with Standard Specification for Clay Flue Lin-ings, ASTM C 315 (ref. 6), a listed chimney lining systemcomplying with Standard for Safety for Chimney Liners, UL1777 (ref. 7) or other approved system or material. Fireclayflue liners are laid in medium-duty refractory mortar con-forming to Standard Test Method for Pier Test for RefractoryMortars, ASTM C 199 (ref. 4), with flush mortar joints on theinside. Care should be taken to use only enough mortar to makethe joint. Flue lining installation should conform to StandardPractice for Installing Clay Flue Lining, ASTM C 1283 (ref. 8).

The chimney wall must be constructed of solid masonryunits or hollow units grouted solid, and be at least 4 in. (102mm) in nominal thickness. The chimney wall should be separatedfrom the flue lining by an airspace or insulation not thicker than

the thickness of the flue lining to permit the flue lining, when hot,to expand freely without cracking the chimney wall. Note that inSeismic Design Categories D and E, additional reinforcementand anchorage requirements apply to masonry chimenys.

To ensure the fireplace draws adequately, flue size isdetermined by the shape of the flue and either the size of thefireplace opening (see Table 3) or the chimney height.

The chimney must extend at least 3 ft (914 mm) above thepoint where the chimney passes through the roof and at least2 ft (610 mm) above any part of the building within 10 ft(3,048 mm) of the chimney (see Figure 2). Higher chimneysmay be required for adequate draft. Good draft is normallyachieved with 15 ft (4,572 mm) high chimneys (measuredfrom the top of the fireplace opening to the top of the chimney).

The chimney must be capped to resist water penetration.A mortar wash that is feathered to the edge of the chimney wallis not an adequate cap. The cap should be either cast-in-placeor precast concrete, as shown in Figure 2. Metal pan flashingover the top of the chimney will also perform adequately.

CLEARANCES AND FIREBLOCKING

Adequate clearance between combustibles and both thefireplace and chimney is important to provide a safe solid fuelburning assembly. A minimum 2 in. (51 mm) airspace must bemaintained between the front faces and sides of masonryfireplaces, or 4 in. (102 mm) from the back face, and anycombustibles, excluding trim and the edges of sheathingmaterials. The IRC (ref. 1) contains minimum clearancesbetween masonry fireplaces or chimneys and exposed com-bustible trim and the edges of sheathing materials such aswood siding, flooring and drywall as well as mantles. Theseair spaces should be firestopped using noncombustible mate-rials as precribed by the building code.

A 2 in. (51 mm) clearance is required around the perim-eter of the chimney wall. This clear space should be firestoppedin the same manner as described for fireplaces. If the entireperimeter of the chimney wall is outside the building, exclud-ing soffits or cornices, the clearance between the chimneywall and combustibles may be reduced to 1 in. (25 mm).

ENERGY EFFICIENCY

Proper fireplace design and operation helps maximizethe efficiency. Maintaining efficient fuel consumption byproperly adjusting the damper is critical. There are severalother ways to significantly improve the performance of theconcrete masonry fireplace. For example, positioning thefireplace on interior rather than exterior walls reduces heat

Table 3—Minimum Flue Net Cross-Sectional Areafor Masonry Fireplaces

Flue shape Net cross-sectional area of flue,fraction of fireplace opening size

Round 1/12

Square 1/10

Rectangular:aspect ratio < 2 to 1 1/10

aspect ratio > 2 to 1 1/8

NATIONAL CONCRETE MASONRY ASSOCIATION To order a complete TEK Manual or TEK Index,13750 Sunrise Valley Drive, Herndon, Virginia 20171 contact NCMA Publications (703) 713-1900www.ncma.org

loss when the fireplace is not in operation,and increases the amount of usable radiantheat from the concrete masonry.

Fireplace efficiency can also be improvedby introducing external air into the fireboxfor draft and combustion. An external com-bustion air system requires a damper in thefirebox, adequate ducting or air passagewaysand a grill or louver at the exterior opening.The external air damper should permit thecontrol of both the direction and volume ofthe airflow for temperature control. Thedamper should be capable of directing airflow towards the back of the firebox so thatwhen down drafts or negative pressures oc-cur, hot ashes or embers are not forced intothe room.

REFERENCES1 . 2000 International Residential Code. In-

ternational Code Council, 2000.2. Standard Classification of Fireclay and

High-Alumina Refractory Brick , ASTMC 27-98. ASTM International, 1998.

3. Standard Specification for Firebox Brickfor Residential Fireplaces, ASTM C 1261-98. ASTM International, 1998.

4. Standard Test Method for Pier Test forRefractory Mortars, ASTM C 199-84(2000). ASTM International, 2000.

5. Book of Successful Fireplaces, How toBuild, Decorate and Use Them, 20th Edition, by R. J. Lytle and Marie-Jeanne Lytle, Structures Publishing Company,Farmington, Michigan, 1977.

6. Standard Specification for Clay Flue Linings, ASTM C 315-02. ASTM International, 2002.7. Standard for Safety for Chimney Liners, UL 1777. Underwriters Laboratory, 1996.8. Standard Practice for Installing Clay Flue Lining, ASTM C 1283-02. ASTM International, 2002.

Figure 2—Chimney Roof Penetration

Sealant and backer rod

Joint fillerConcrete cap

Temporary forming

Counter flashing

2 in. (51 mm), min.Precast cap

Roof rafter

Base flashing (fire stop)Fire clay flue linerAir space

Chimney blockConcrete brick1

2 in. (13 mm) non-combustible wall board (fire stop)

Ceiling joist

Cast-in-Place Cap: Precast Cap:

24 in. (610 mm) min.

36 in. (914 mm) min.

D R A F T

4-2A: ESTIMATING CONCRETE MASONRY MATERIALS

INTRODUCTION

Estimating the quantity or volume of materials used in a typical masonry project can range from therelatively simple task associated with an unreinforced single wythe garden wall, to the comparativelydifficult undertaking of a partially grouted multiwythe wall coliseum constructed of varying unit sizes,shapes, and configurations.

Large projects, due to their complexity in layout and detailing, often require detailed computerestimating programs or an intimate knowledge of the project to achieve a reasonable estimate of thematerials required for construction. However, for smaller projects, or as a general means of obtainingballpark estimates, the rule of thumb methods described in this TEK provide a practical means ofdetermining the quantity of materials required for a specific masonry construction project.

It should be stressed that the information for estimating materials quantities in this section should beused with caution and checked against rational judgment. Design issues such as non-modular layouts ornumerous returns and corners can significantly increase the number of units and the volume of mortar orgrout required. Often, material estimating is best left to an experienced professional who has developeda second hand disposition for estimating masonry material requirements.

ESTIMATING CONCRETE MASONRY UNITS

Probably the most straightforward material to estimate for most masonry construction projects is theunits themselves. The most direct means of determining the number of concrete masonry units neededfor any project is to simply determine the total square footage of each wall and divide by the surfacearea provided by a single unit specified for the project.

For conventional units having nominal heights of 8 in. (203 mm) and nominal lengths of 16 in. (406mm), the exposed surface area of a single unit in the wall is 8/9 ft2 (0.083 m2). Including a 5 percent

allowance for waste and breakage, this translates to 119 units per 100 ft2 (9.29 m2) of wall area. (See Table 1 for these and other values.) Because this method of determining the necessary number ofconcrete masonry units for a given project is independent of the unit width, it can be applied toestimating the number of units required regardless of their width.

Provided by: Featherlite Building Products

Keywords: concrete masonry units, construction, estimating, grout, mortar

Table 1—Approximate Number of Concrete Masonry Units Required for Single Wythe

Constructiona

Unittype

Unit facesize, in. (mm)

Number of units per

100 ft2 (100 m2) ofwall area

Page 1 of 74-2A: ESTIMATING CONCRETE MASONRY MATERIALS

2/10/2005http://www.ncma.org/etek/TEKs/T4-2AF.cfm?Referer=featherlitetexas.com

When using this estimating method, the area of windows, doors and other wall openings needs to besubtracted from the total wall area to yield the net masonry surface. Similarly, if varying unitconfigurations, such as pilaster units, corner units or bond beam units are to be incorporated into theproject, the number of units used in these applications need to be calculated separately and subtractedfrom the total number of units required.

ESTIMATING MORTAR MATERIALS

conventionalhalf-high

half-lengthbrick

8 x 16 (203 x 406)

4 x 16 (102 x 406)

8 x 8 (203 x 203)22/3 x 8 (68 x

203)

119 (1,275) 238 (2,550) 238 (2,550)710 (7,610)

a based on net area of masonry wall, includes about 5% waste

Table 2—Mortar Estimation for Single Wythe Concrete Masonry Wallsa

Mortar type & batch proportions

Approximate number ofunits that can be laid using one batch of

mortar

ConventionalCMU:

Brick-sized CMU:

Masonry cement: 8-70 lb (31.8 kg) bags masonry cement, 1 ton (907 kg) sandb 240 1,000 Preblended mortar: 1-80 lb (36.3 kg) bag 1-3,000 lb (1,361 kg) bag

16420

501,550

Site-mixed mortarc: Portland cement-lime: Type M 1 ft3 portland cement, 1/4 ft3 hydrated lime, 3 3/4ft3 sand Type S 1 ft3 portland cement, 1/2 ft3 hydrated lime, 41/2ft3 sand Type N 1 ft3 portland cement, 1 ft3 hydrated lime, 6 ft3sand Type O 1 ft3 portland cement, 2 ft3 hydrated lime, 9 ft3

38

46

62

187

225

300



Next to grout, mortar is probably the most commonly misestimated masonry construction material.

sand 93 450 Mortar cement: Type M 1 ft3 portland cement, 1 ft3 Type N mortar cement, 6 ft3 sand, or

1 ft3 Type M mortar cement, 3 ft3 sand Type S

1/2 ft3 portland cement, 1 ft3 Type N mortar

cement, 41/2 ft3 sand, or

1 ft3 Type S mortar cement, 3 ft3 sand Type N or O 1 ft3 Type N mortar cement, 3 ft3 sand

6231

4631

31

300150

225150

150 Masonry cement: Type M 1 ft3 portland cement, 1 ft3 Type N masonry cement, 6 ft3 sand, or 1 ft3 Type M masonry cement, 3 ft3 sand Type S

1/2 ft3 portland cement, 1 ft3 Type N masonry

cement, 41/2 ft3 sand, or

1 ft3 Type S masonry cement, 3 ft3 sand Type N or O 1 ft3 Type N masonry cement, 3 ft3 sand

6231

4631

31

300150

225150

150a Number of units can vary from those listed in the table, based on factors such as the skill level of the mason, non-modular layouts, numerous returns and corners, etc. Values include nominal amounts for waste. Assumes face shell mortar bedding for conventional concrete masonry units and full bedding for brick-sized concrete masonry units. 1 ft3 = 0.0283 m3.

b 1 ton (907 kg) damp loose sand = 25 ft3 (0.71 m3)c For conversion purposes, the following can be used: Portland cement: typical bag volume = 1 ft3 (0.028 m3); typical bag weight 94 lb (42.6 kg); typical density 94 lb/ft3 (1,506 kg/m3) Hydrated mason's lime: typical bag volume = 11/4 ft3 (0.035 m3); typical

bag weight 50 lb (22.7 kg); typical density 40 lb/ft3 (641 kg/m3) Sand: 1 ft3 is equivalent to about 7 shovelfuls; typical density of damp loose sand 80 lb/ft3 (1,281 kg/m3) Masonry and mortar cement bag weights vary, although commonly: Type N masonry cements and mortar cements are packaged in 70 lb (31.8 kg) bags; Type S masonry cements and mortar cements are packaged in 75 lb (34.0 kg) bags; Type M masonry cements and mortar cements are packaged in 80 lb (36.3 kg) bags.



Variables such as site batching versus pre-bagged mortar, mortar proportions, construction conditions,unit tolerances and work stoppages, combined with numerous other variables can lead to largedeviations in the quantity of mortar required for comparable jobs.

As such, masons have developed general rules of thumb for estimating the quantity of mortar required tolay concrete masonry units. These general guidelines are as follows for various mortar types. Note thatthe following estimates assume the concrete masonry units are laid with face shell mortar bedding;hence, the estimates are independent of the concrete masonry unit width.

Masonry cement mortar

Masonry cement is typically available in bag weights of 70, 75 or 80 lb (31.8, 34.0 and 36.3 kg),although other weights may be available as well. One 70 lb (31.8 kg) bag of masonry cement willgenerally lay approximately 30 hollow units if face shell bedding is used. For common batchingproportions, 1 ton (2,000 lb, 907 kg) of masonry sand is required for every 8 bags of masonry cement. Ifmore than 3 tons (2,721 kg) of sand is used, add 1/2 ton (454 kg) to account for waste. For smaller sandamounts, simply round up to account for waste. This equates to about 240 concrete masonry units perton of sand.

Preblended mortar

Preblended mortar mixes may contain portland cement and lime, masonry cement or mortar cement, andwill always include dried masonry sand. Packaged dry, the mortars typically are available in 60 to 80 lb(27.2 to 36.3 kg) bags or in bulk volumes of 2,000 and 3,000 lb (907 and 1,361 kg).

Portland cement lime mortar

One 94 lb (42.6 kg) bag of portland cement, mixed in proportion with sand and lime to yield a lean TypeS or rich Type N mortar, will lay approximately 62 hollow units if face shell bedding is used. This assumes a proportion of one 94 lb (42.6 kg) bag of portland cement to approximately one-half of a 50 lb(22.7 kg) bag hydrated lime to 4 1/4 ft3 (0.12 m3) of sand. For ease of measuring in the field, sand

volumes are often correlated to an equivalent number of shovels using a cubic foot (0.03 m3) box, as shown in Figure 1.



ESTIMATING GROUT

The quantity of grout required on a specific job can vary greatly depending upon the specificcircumstances of the project. The properties and configuration of the units used in construction can havea huge impact alone. For example, units of low density concrete tend to absorb more water from the mixthan comparable units of higher density. Further, the method of delivering grout to a masonry wall(pumping versus bucketing) can introduce different amounts of waste. Although the absolute volume ofgrout waste seen on a large project may be larger than a comparable small project, smaller projects mayexperience a larger percentage of grout waste.

Table 3 provides guidance for the required volume of grout necessary to fill the vertical cells of walls ofvarying thickness. Additional grout may be necessary for horizontally grouting discrete courses ofmasonry. Note that walls constructed of 4-in. (102-mm) masonry units are not included in Table 3. Dueto the small cell size and difficulty in adequately placing and consolidating the grout, it is notrecommended to grout conventional 4-in. (102-mm) units.

Figure 1—Measuring Mortar Sand Volume

Table 3—Grout Volume Estimation for Hollow Single Wythe Concrete Masonry Walls

Volume of grout, ft3 per 100 ft2 of wall (m3 per 100 m2)a

Groutspacing,in. (mm)

6 in. (152 mm)

8 in. (203 mm)

Wall width: 10 in. (254

mm)12 in. (305

mm) 14 in. (356

mm)8 (203) 25.6 (7.8) 36.1 (11.0) 47.0 (14.3) 58.9 (18.0) 74.5 (22.7)16 (406) 12.8 (3.9) 18.1 (5.5) 23.5 (7.2) 29.5 (9.0) 37.3 (11.4)24 (610) 8.6 (2.6) 12.1 (3.7) 15.7 (4.8) 19.7 (6.0) 24.8 (7.6)32 (813) 6.4 (2.0) 9.1 (2.8) 11.8 (3.6) 14.8 (4.5) 18.6 (5.7)

40 (1,016) 5.2 (1.6) 7.3 (2.2) 9.4 (2.9) 11.8 (3.6) 14.9 (4.5)48 (1,219) 4.3 (1.3) 6.1 (1.9) 7.9 (2.4) 9.9 (3.0) 12.4 (3.8)



Tables 4 and 5 contain estimated yields for bagged preblended grouts for vertical and horizontalgrouting, respectively.

REFERENCES

56 (1,422) 3.7 (1.1) 5.2 (1.6) 6.8 (2.1) 8.5 (2.6) 10.6 (3.2)64 (1,626) 3.2 (1.0) 4.6 (1.4) 5.9 (1.8) 7.4 (2.3) 9.3 (2.8)72 (1,829) 2.9 (0.9) 4.1 (1.2) 5.3 (1.6) 6.6 (2.0) 8.3 (2.5)80 (2,032) 2.6 (0.8) 3.7 (1.1) 4.7 (1.4) 5.9 (1.8) 7.5 (2.3)88 (2,235) 2.4 (0.7) 3.3 (1.0) 4.3 (1.3) 5.4 (1.6) 6.8 (2.1)96 (2,438) 2.2 (0.7) 3.1 (0.9) 4.0 (1.2) 5.0 (1.5) 6.2 (1.9)104 (2,642) 2.0 (0.6) 2.8 (0.9) 3.7 (1.1) 4.6 (1.4) 5.7 (1.7)112 (2,845) 1.9 (0.6) 2.6 (0.8) 3.4 (1.0) 4.3 (1.3) 5.3 (1.6)120 (3,048) 1.8 (0.5) 2.5 (0.8) 3.2 (1.0) 4.0 (1.2) 4.9 (1.5)

a Assumes two-core hollow concrete masonry units and 3% waste.

Table 4—Grout Estimation for Hollow Single Wythe Concrete Masonry Walls, Vertical

Grouting with Preblended Grouta

CMU size,in. (mm)

Yield, number of cores 80 lb (36.3 kg)

bag 3,000 lb (1,361 kg)

bag6 (152) 3.6 1508 (203) 2.7 11010 (254) 2.2 9512 (305) 1.8 80

a 80 lb (36.3 kg) bag yields approximately 0.66 ft3 (0.019 m3); 3,000 lb (1,361 kg) bag yields approximately 25 ft3 (0.71 m3)

Table 5—Grout Estimation for Hollow Single Wythe Concrete Masonry Walls, Horizontal

(Bond Beam) Grouting with Preblended Grouta

CMU size,in. (mm)

Yield, number of cores 80 lb (36.3 kg)

bag 3,000 lb (1,361 kg)

bag6 (152) 2.7 (0.823) 100 (30.48)8 (203) 2.0 (0.609) 80 (24.38)12 (305) 1.6 (0.488) 60 (18.29)

a 80 lb (36.3 kg) bag yields approximately 0.66 ft3 (0.019 m3); 3,000 lb (1,361 kg) bag yields approximately 25 ft3 (0.71 m3)



Disclaimer: Although care has been taken to ensure the enclosed information is as accurate and complete as possible, NCMA does not assume responsibility for errors or omissions resulting from the use of this TEK.

Provided by: Featherlite Building Products

1. Kreh, D. Building With Masonry, Brick, Block and Concrete. The Taunton Press, 1998.2. Annotated Design and Construction Details for Concrete Masonry, TR 90B. National Concrete

Masonry Association, 2003.



TEK 5-7A © 2001 National Concrete Masonry Association (replaces TEK 5-7 and TEK 17-5 )


FLOOR AND ROOF CONNECTIONS TOCONCRETE MASONRY WALLS

TEK 5-7A Details (2001)

Keywords: connections, floor systems, hollowcore,joists, ledger, loadbearing concrete masonry, pocket,roof systems, trusses

INTRODUCTION

Floor and roof systems for use with loadbearing struc-tural concrete masonry walls serve three primary functions:they transmit the vertical dead load and live load to the bearingwalls; they function as diaphragms, transmitting lateral windand seismic loading through the walls to the foundation; andthey act to support the walls from out-of-plane loads. Inaddition to these structural functions, floors and roofs shouldprovide a satisfactory barrier to the transmission of sound,fire, and heat. The many types of floor and roof systems in usetoday are designed to satisfy all of these requirements in aneconomical manner.

CONNECTIONS

The transfer of loads between diaphragms and wallsrequires the proper design and detailing of the connectionlinking these elements. Connections critical to the integrityof a structure. The connections detailed herein addressminimal requirements. Additional requirements may benecessary in some locals, particularly where earthquake andhigh wind forces are to be resisted. The four primary types ofconnections, each having specific advantages, include:· Direct Bearing Connection – The direct bearing connec-tion is often the simplest type of connection. This connec-tion is used at the top of concrete masonry walls or when achange in wall thickness provides a ledge with sufficientbearing area as shown in Figure 1.· Pocket Connection – A pocket connection consists offraming the floor or roof system into a void in the masonrywall. This detail is used when masonry continues above(either as part of the wall or as a parapet) the connectionlocation and eccentricity is to be minimized. Care must betaken to insure that the use of a pocket does not interfere withthe continuity of the vertical reinforcement in the wall.· Hanger Connection – When it is desired to maintain thecontinuity of the wall for structural, aesthetic, or construc-tion reasons, a wall hanger can be used to suspend the roof or

floor system. Hangers are generally anchored to a wallthrough a joint and into a bond beam. However, hangersapproved for direct attachment to the surface of a masonrywall are also available.· Ledger Connection – As with hangers, ledger connec-tions minimize the impact on the continuity of a masonrywall. A ledger connection reduces the necessary pre-plan-ning and does not unduly impact the mason’s work as opposedto a pocket connection; thereby reducing the number of fieldmodifications.

Note: Most of the connections herein depict flashing forwater penetration resistance which should be used in all exteriorwalls. Normally flashing is not provided in interior walls.

FLOOR AND ROOFING SYSTEMS

Several materials are common to roof and floor con-struction. Wood, concrete, and steel are among the mostfrequently used framing materials in these applications.

Wood SystemsWood framed floors and roofs are common in residen-

tial and low-rise construction. It is imperative when con-structing a wood-framed system that it not be in directcontact with the concrete masonry. Wood in contact withmasonry materials may absorb moisture present in the con-crete masonry causing the wood to rot. To prevent theresulting unwanted decay, the lumber used should be pres-sure-treated, naturally decay resistant, or have a moisturebarrier placed between the wood and the concrete masonry.

Steel SystemsSteel-framed roofs using steel bar joints are very com-

mon in commercial structures because they are capable ofspanning long distances. Steel bar joists typically use pock-eted or ledger connections to concrete masonry walls. Pro-prietary systems that use concrete masonry units as a fillerbetween the steel joists are also available.

Concrete SystemsConcrete slabs can take many forms, including pre-

stressed, precast, and cast-in-place construction. Dependingupon the size and number of stories associated with a given

Wood joist

Anchorage as required

Toenail or tie as required

Reinforced bond beam

Sill (pressure treated

Concrete masonry wall

or provide moisture barrier)

Blocking or band joistSuperstructure

Reinforced

staggered anchorDouble (shown) or

Ledger

Joist hanger

bolt as required

Sheathing

Wood joist

Solid or filledunit to supportflashing

bond beam

Grout stop

at 32 in. (814 mm)

Cavity fill or other

1 in. (25 mm) partiallyopen "L" shaped headjoints for weeps

Drip edge

mortar collection device

2 in. (51 mm) deep


Bond beam

Wood Truss

Notch/pocket

Provide gap or moisturebarrier as required

Reinforcement

at 32 in. (814 mm)

Drip edge

joints for weeps

partially open1 in. (25 mm)

"L" shaped head

collection device

Cavity fill orother mortar

inside of faceshellStop flashing at

o.c.

Reinforced

Joist hanger; fasten as required by

Wood joist

Sheathing

bond beam

hanger manufacturer

Cavity fill or other mortar


collection device

Drip edge

4 in. (102 mm) unit (solid or filled) tosupport flashing


Void/pocket

unit to support flashing

Concrete masonry bond beam

Fire-cut end of joist(as required)

provide moisture barrierPressure treated or

Reinforcement

Sheathing

Solid or filled masonry

Grout stop

1 in. (25 mm)

"L" shaped headpartially open

joints for weeps

Drip edge

at 32 in. (814 mm)o.c.

other mortarCavity fill or

collection device

Stop flashing at inside of faceshell

Wood joistFigure 1—Direct Bearing Wood Floor Joist (ref. 2)

Figure 2—Direct Bearing Wood Floor Joist

Figure 3—Wood Floor Joist Hanger (ref. 2)

Figure 4—Wood Floor Truss Hanger (ref. 2)

Figure 5—Wood Floor Joist With Pocket

Figure 6—Wood Ledger and Hanger

Figure 7—Wood Floor Truss Pocket (ref. 2)

Blocking or band joist

Sill (pressure treated or

Anchorage as required


Wood joist


Provide gap or moisturebarrier as required

provide moisture barrier)

of faceshellStop flashing at inside

Sheathing

as required

Drip edge

open "L" shaped head1 in. (25 mm) partially

joints for weeps

Cavity fill or other mortarcollection device

(solid or filled) to4 in. (102 mm) unit

support flashing

Toe nail or tie at 32 in. (814 mm)


Wood truss

Bearing truss hanger;fasten as required by hangermanufacturerConcrete

4 in. (102 mm) unit (solid orfilled) to support flashing

other mortarCavity fill or

collection device

"L" shaped head

1 in. (25 mm)partially open

joints for weeps

Drip edge

at 32 in. (814 mm)


o.c.

masonry wall

Bond beam

Anchor bolt or


Sill (pressure treated or

specialty anchoras required

provide moisture barrier)

code or useToenail per

rated connector

o

o

o

+

++

+

Reinforced bond beamConcrete masonry wall

as requiredUplift connectorMoisture barrier

Anchor bolts spaced as required


angleSteel


to steel Decking attached

required forangle as

shear transferdiaphragm

bolted to wallSteel ledger angle

Isolation joint


Steel bar joist welded orbolted to ledger angle

at 32 in. (814 mm)


Drip edge

Wood Nailer with anchor bolts

Sloping sheet metal copingcap with cont. cleat. each side

Attachment strip

Grout cores solid at anchor bolts

Counter flashing

Stop flashing at inside offaceshell (see TEK 19-2A)

CantParapet flashing

SealantRoofing membrane

Steel bar joist weldedor bolted to bearingplate

Sealant

at 32 in. (814 mm)

Standard unit withinside faceshell and


1 in. (25 mm) partiallyopen "L" shaped head

part of web removed

joints for weeps

Drip edge

collection device

plate with anchoraround joist steelSolid unit notched


Masonry wall

Grout stop

Parapet flashing

Attachment strip

Counter flashing

CantSealant

cap with cont. cleat. each sideSloping sheet metal coping

Wood Nailer with anchor bolts


or bolted to bearingSteel bar joist welded

plate

joints for weepsReinforced bond beam

Drip edge

at 32 in. (814 mm) o.c.


open "L" shaped head1 in. (25 mm) partiallycollection device

Wall ties (typ.)

Insulation

Reinforced lintel

Steel shelf angle

Sealant at top offlashing unless self

tuck into mortar jointadhearing flashing or

(114 mm) max. cavity2 in. (51 mm) min. to 4 / in. 1

2

Figure 8—Wood Roof Truss with Top Plate (ref. 2)

Figure 9—Wood Roof Truss with EmbeddedStrap Anchor (ref. 2)

Figure 10—Steel Joist Direct Bearing on Cavity Wall

Figure 11—Steel Joist with Pocket (ref. 3, 4, 5)

Figure 12—Steel Joist with Ledger Angle

Figure 13—Steel Joist at Sidewall


project, one concrete framing system may have unique ben-efits over another. For example, hollow core prestressedslabs can be erected quickly, without the need for formworkor shoring. Where sufficient space is available at the job site,precast slabs can be formed in stacks on-site, starting with theroof slab and using the top surface of the lower slab as theform for the next slab. Once cured, the precast slabs are liftedto their final location. The use of cast-in-place concretefloors and roofs, because of the time needed for forming,pouring, finishing, and curing, requires a building plan whichis large enough to permit the masonry work to progress in onepart of the structure while the floor in another area is com-pleted.

Precast hollow core slab

Hooked shear bar grouted in slab keyway

of faceshell (see TEK 19-2A)Stop flashing at inside

or filled) to support flashing4 in. (25 mm) unit (solid

Topping if requiredat 32 in. (814 mm)



Drip edge

collection device

Bearing stripHooked bar in wall at shear

Reinforcedbond beam

bar (not required if verticalreinforcement at this location)

Grout stop

o.c.


Reinforcement with hookson both ends grouted

of faceshell (see TEK 19-2A)Stop flashing at inside

or filled) to support flashing4 in. (25 mm) unit (solid

Topping if requiredat 32 in. (814 mm) o.c.



Drip edge

collection device

Hooked bar in wall at shear

Reinforcedbond beam

bar (not required if verticalreinforcement at this location)

Grout stop

Grouted cells at location ofshear bar

into broken core

Figure 14—Concrete Hollowcore at Bearing (ref. 3) Figure 15—Hollowcore at Sidewall (ref. 3)

REFERENCES1. Architectural and Engineering Concrete Masonry De-tails for Building Construction, TR-95. National ConcreteMasonry Association, 1973.2. Concrete Masonry Homes: Recommended Practices.U.S Department of Housing and Urban Development, Officeof Policy Development and Research, 1999.3. Design for Dry Single-Wythe Concrete Masonry Walls,TEK 19-2A. National Concrete Masonry Association, 1998.4. Flashing Details for Concrete Masonry Walls, TEK19-5A. National Concrete Masonry Association, 2000.5. Generic Wall Design for Single-Wythe LoadbearingWalls. Masonry Institute of Michigan, 2000.

Keywords: cavity wall, insulation, multi-wythe wall,thermal properties, R-values

R-VALUES OF MULTI-WYTHECONCRETE MASONRY WALLS

TEK 6-1AEnergy & IAQ (2001)


heat loss due to air infiltration into the building.

CAVITY WALLS

Typical cavity walls are constructed with a 4, 6, 8, or 12in. (102, 152, 203, or 305 mm) concrete masonry backupwythe, a 2 to 41/2 in. (51 to 114 mm) wide cavity, and a 4 in.(102 mm) masonry veneer. Building Code Requirements forMasonry Structures (ref. 3) allows cavity widths up to 41/2 in.(114 mm), beyond which a detailed wall tie analysis must beperformed.

When placing rigid board insulation in the cavity, aminimum 1 in. (25 mm) clear airspace (2 in. (51 mm) ispreferred) between the insulation and the outer wythe isrecommended to ensure proper drainage in the event waterenters the wall. Perlite and vermiculite loose fills can occupythe entire cavity space since these materials allow water todrain freely through them. For this reason, these insulationmaterials are typically treated for water repellency. Whenloose fill insulation is used, screens placed over the weepholes or wicks should be used to contain the fill whileallowing water to drain freely out of the weep holes.

R-VALUE TABLES

Table 1 presents R-values of uninsulated concrete ma-sonry cavity walls with 4, 6, 8, and 12 in. (102, 152, 203, and305 mm) backup wythes and 4 in. (102 mm) concretemasonry veneer. These R-values should be added to theapplicable R-values in Tables 2 and 3 to account for cavityinsulation and/or interior furring with insulation. Table 4contains the thermal data used to develop the tables.

As an example, to determine the R-value of a concretemasonry cavity wall with 8 in. (152 mm) 105 pcf (1682 kg/m3) backup insulated with 2 in. (51 mm) of extruded polysty-rene insulation in the cavity, first determine the R-value of theuninsulated wall from Table 1 (4.0 ft2.hr.oF/Btu, 0.70 m2.K/W), then add the cavity insulation R-value from Table 2 (10ft2.hr.oF/Btu, 1.8 m2.K/W), to obtain the total R-value of 14.0ft2.hr.oF/Btu (2.5 m2.K/W).

Calculations are performed using the series-parallel(also called isothermal planes) calculation method recom-mended by the American Society of Heating, Refrigerating,

INTRODUCTION

R-values of building components are used to estimate abuilding's energy consumption under steady-state conditions.In order to estimate a building's actual energy consumption,however, the effects of building design, thermal mass, andclimate, among other factors, must be included.

R-value is an estimate of the overall steady-state resis-tance to heat transfer. It is determined in the laboratory byapplying a constant temperature difference across a wallsection, then measuring the steady state heat flow through thewall under this condition. For design, calculation methodshave been developed to aid in determining R-values of variousbuilding systems (ref. 1).

The thermal mass of concrete masonry walls cansignificantly reduce energy consumption. Thermal masseffects are determined primarily by the properties of theconstruction materials used, the climate, building type,and the position of the insulation within the wall. Con-crete masonry buildings often require significantly lowerinsulation levels because of thermal mass. Energy codesand standards such as ASHRAE Standards 90.1 and 90.2(refs. 4, 5) and the International Energy ConservationCode (ref. 6) permit concrete masonry walls to have lowerR-values than frame wall systems to achieve the samelevel of energy efficiency.

Concrete masonry cavity walls provide a wide array ofoptions for including insulation to obtain high R-values.Typically, the cavity is insulated with rigid board or withmineral loose-fill insulation. Cavity walls are also builtwith insulation in the cores of masonry units leaving theentire cavity space open for drainage. In addition, furringwith rigid board or mineral fiber batt insulation can beinstalled on the interior side of the wall to further increasewall R-values.

Placing insulation between two wythes of masonryoffers maximum protection for the insulation. High R-values are easily obtainable, since the cavity installationallows a continuous layer of insulation to envelop themasonry. This continuous insulation layer can also reduce


Table 2—R-Values of Cavity Insulation(a)

Insulation Insulation R-valuetype thickness, in. (hr.ft2.oF/Btu)

Vermiculite loose fill 1 1.32 3.63 5.8

41/2 9.3Perlite loose fill 1 2.2

2 5.33 8.4

41/2 13.1Extruded polystyrene(b) 1 5.0

11/2 7.52 10.0

21/2 12.53 15.0

31/2 17.5Polyisocyanurate(c) 1 8.7

11/2 12.32 15.8

21/2 19.33 22.8

31/2 26.3

(a) These values should be added to the values presented in Table1 to achieve the total R-value of an insulated cavity wall.

(b) A minimum 1 in. (25 mm) nonreflective air space is includedin the values in Table 1.

(c) Values adjusted to include a 1 in. (25 mm) reflective air space.

Table 1—R-Values of Uninsulated Cavity Walls With 4 in. Concrete Masonry Veneer (ft2.hr.oF/Btu)(a)

Nominalthickness of Density of concrete used in concrete masonry backup unit (pcf):backup, in. 85 95 105 115 125 135

range mid range mid range mid range mid range mid range mid4 3.8-4.1 3.9 3.7-4.0 3.8 3.6-3.9 3.7 3.5-3.8 3.6 3.4-3.7 3.5 3.3-3.6 3.46 4.1-4.3 4.2 3.9-4.2 4.0 3.8-4.1 3.9 3.7-3.9 3.8 3.5-3.8 3.7 3.4-3.7 3.58 4.2-4.5 4.4 4.1-4.4 4.2 3.9-4.2 4.0 3.8-4.1 3.9 3.7-4.0 3.8 3.6-3.9 3.710 4.3-4.7 4.5 4.2-4.5 4.3 4.0-4.3 4.1 3.8-4.2 4.0 3.8-4.0 3.8 3.6-4.0 3.812 4.4-4.8 4.6 4.2-4.6 4.4 4.1-4.4 4.2 4.0-4.3 4.1 3.8-4.2 4.0 3.7-4.0 3.8

(a) (ft2.hr.oF/Btu)(0.176) = m2.K/W. Includes a minimum 1 in. (25 mm) nonreflective air space. Mortar joints are assumed to be 3/8 in.(9.5 mm) thick, with full mortar bedding on 4 in. (102 mm) units, and face shell bedding on hollow backup units.

These published values reflect a compendium of histori-cal data on thermal conductivity of concrete (refs. 1, 9).Locally available products and local conditions may result inthermal values which fall outside of this range. The middle-of-the-range values are presented for use in cases where moreaccurate values are not available from local manufacturers.

The values in Table 1 are based on an ungrouted backupwythe. However, the addition of grout to a hollow concretemasonry backup wythe does not significantly affect theoverall R-value of an insulated cavity wall. For example, theR-value of a cavity wall with 8 in. (203 mm) ungrouted 105pcf (1682 kg/m3) backup and 2 in. (51 mm) of perlite in thecavity is 9.3 hr.ft2.oF/Btu (1.72 m2.K/W). When the backupwythe is grouted solid, the R-value becomes 8.8 hr.ft2.oF/Btu(1.67 m2.K/W), a decrease of about 5 percent.

and Air-Conditioning Engineers (refs. 1, 8). The methodaccounts for the thermal bridging that occurs through thewebs of concrete masonry units and is briefly described on thefollowing page.

Thermal values for concrete masonry walls are corre-lated to density, since the thermal conductivity of concreteincreases with increasing concrete density. For each den-sity, Table 1 lists a range of R-values as well as a single value,which represents the middle of the range.

A range of thermal values is appropriate for concreteproducts because the thermal conductivity of concretecannot always be accurately estimated from density alone.The thermal conductivity of concrete varies with aggre-gate type(s) used in the concrete mix, the mix design,moisture content, etc.

Table 3—R-Values of Finish Systems(a)

System: R-value (hr.ft2.oF/Btu)1/2 in. gypsum board on furring 1.41/2 in. foil-faced gypsum board 2.9

on furring

Wood furring, insulation, Spacing of furring strips:and 1/2 in. gypsum wallboard: 16 in. o.c. 24 in. o.c.3/4 in. extruded polystyrene(b) 5.2 5.23/4 in. polyisocyanurate(c) 8.0 8.111/2 in. extruded polystyrene(b) 8.9 8.911/2 in. polyisocyanurate(c) 13.2 13.4R-11 mineral fiber batt 9.6 10.2R-13 mineral fiber batt 10.8 11.6R-15 mineral fiber batt 11.9 12.9R-19 mineral fiber batt 15.9 16.9R-21 mineral fiber batt 17.1 18.3

Metal furring, insulation,and 1/2 in. gypsum wallboard(d):R-11 mineral fiber batt 6.0 7.1R-13 mineral fiber batt 6.5 7.7R-15 mineral fiber batt 6.9 8.3R-19 mineral fiber batt 7.6 9.1R-21 mineral fiber batt 7.9 9.5

(a) Values should be added to those presented in Table 1 toachieve the total R-value of a cavity wall with a finish applied.

(b) Values include a 3/4 in. (19 mm) nonreflective air space.(c) Values include a 3/4 in. (19 mm) reflective air space.(d) Values from ref. 4, Appendix A.

where:a

c= fractional web area, Figure 1, Section A-A

af

= fractional face shell area, Figure 1, elevationa

m= fractional mortar joint area, Figure 1, elevation

aw

= fractional core area, Figure 1, Section A-AR

a= thermal resistance of cavity

Rc

= thermal resistance of coresR

f= thermal resistance of both face shells, r

c x (2t

fs)

Ri

= thermal resistance of inside air surface filmR

m= thermal resistance of mortar joint, r

m x (2t

fs)

R-VALUE CALCULATION

For estimating R-values of concrete masonry walls, the series-parallel calculation method is recommended (refs. 1, 8). Theseries-parallel calculation treats the block as a series of thermal layers, as illustrated in Figure 1. The face shells formcontinuous outer layers, which are in series with the layer containing webs and cores. The webs and cores form parallel pathsfor heat flow within this thermal layer. The total R-value, R

T, of the block is the sum of the R-values of each layer, as outlined

below. Note: When the core is partially filled (i.e. when using insulation inserts), break the core into multiple layers.

R RR R

a R a R

R R

a R a RR R RT i

f m

f m m f

w c

c w w ca v o= +

++

++ + +

Material: Thermal resistivity (hr.ft2.oF/Btu.in)Vermiculite 2.27Perlite 3.13Extruded polystyrene 5.00Cellular polyisocyanurate, gas-impermeable facer 7.04Concrete:

85 pcf 0.23-0.3495 pcf 0.18-0.28105 pcf 0.14-0.23115 pcf 0.11-0.19125 pcf 0.08-0.15135 pcf 0.07-0.12

Mortar 0.20

Material: R-value (hr.ft2.oF/Btu)1/2 in. gypsum wallboard 0.45Surface air films:

inside 0.68outside 0.17

Air spaces:nonreflective 0.97reflective 2.67

4 in. concrete masonry exterior wythe 0.84

Table 4—Thermal Data Used to Develop Tables

Ro

= thermal resistance of outside air surface filmR

T= total thermal resistance of wall

Rv

= thermal resistance of veneerR

w= thermal resistance of concrete webs, r

c x t

w

rc

= thermal resistivity of concreter

m= thermal resistivity of mortar

tfs

= face shell thicknesstw

= length of concrete webs

Figure 1—Thermal Model of Concrete Masonry Units for R-Value Calculation

tw

tfs

tfs

AA

Elevation of unit face

Section A-A

REFERENCES1. ASHRAE Fundamentals Handbook. Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning

Engineers, Inc., 2001.2. 90.1 User's Manual, Atlanta, Georgia: American Society of Heating, Refrigerating, and Air-Conditioning Engineers, 2000.3. Building Code Requirements for Masonry Structures, ACI 530-02/ASCE 5-02/TMS 402-02. Reported by the Masonry

Standards Joint Committee, 2002.4. Energy Standard for Buildings Except Low-Rise Residential Buildings, ASHRAE/IES 90.1-1999. Atlanta, GA: American

Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. and Illuminating Engineering Society of NorthAmerica, 1999.

5. Energy-Efficient Design of New Low-Rise Residential Buildings, ASHRAE 90.2-1993. Atlanta, GA: American Society ofHeating, Refrigerating and Air-Conditioning Engineers, Inc., 1993.

6. International Energy Conservation Code. International Code Council, 2000.7. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90-01. American Society for Testing and

Materials, 2001.8. Valore, Rudolph C. Calculation of U-Values of Hollow Concrete Masonry. Concrete International, February, 1980, pp 40-

63.9. Valore, Rudolph C. The Thermophysical Properties of Masonry and Its Constituents, Parts I and II. Washington, DC:

International Masonry Institute, 1988.


NATIONAL CONCRETE MASONRY ASSOCIATION2302 Horse Pen Road, Herndon, Virginia 22071-3499


TEK 6-2AEnergy & IAQ (1996)

R-VALUES FOR SINGLE WYTHECONCRETE MASONRY WALLS

through the webs of concrete masonry units. R-values of thevarious finish systems are added to these base values. Todetermine R-values for walls with 2 in. (51 mm) of rigidinsulation (expanded polystyrene, extruded polystyrene, orpolyisocyanurate) rather than the 1 in. (25 mm) shown in thetables, simply add the appropriate insulation thermal resistiv-ity value from Table 6 to the R-values in Tables 2 through 5.

R-values of concrete masonry walls are correlated toconcrete density, since thermal conductivity of concrete in-creases with increasing density. Tables 2 through 5 list arange of R-values for each density, as well as a single value,which represents a calculated middle of the range. The U-factoris determined by simply inverting the R-value (i.e., U = 1/R).

A range of thermal values is appropriate for concreteproducts because the thermal conductivity of concrete cannotalways be accurately estimated from density alone. Thethermal conductivity of concrete varies with aggregate type(s)used in the concrete mix, the mix design, moisture content, etc.

These published values reflect a compendium of histori-cal data on thermal conductivity of concrete (refs. 1,3).Locally available products and local conditions may result inthermal values which fall outside of this range. The middle-of-the-range values are presented for use in cases where moreaccurate values are not available from local manufacturers.

TEK 6-2A © 1996 National Concrete Masonry Association(continued on back page)

Hor

izon

tal

grou

t sp

acin

g, i

n. (

mm

)

Table 1—Percent Ungrouted Area/Percent GroutedArea For Partially Grouted Walls

Vertical grout spacing, in. (mm)no vert. 48 40 32 24 16grout (1219) (1016) (813) (610) (406)

no horiz. 100 83 80 75 67 50grout 0 17 20 25 33 50

48 (1219) 83 69 67 63 56 4217 31 33 37 44 58

40 (1016) 80 67 64 60 53 4020 33 36 40 47 60

32 (813) 75 63 60 56 50 3725 37 40 44 50 63

24 (610) 67 56 53 50 44 3333 44 47 50 56 67

16 (406) 50 42 40 37 33 2550 58 60 63 67 75

INTRODUCTION

Concrete masonry walls are often constructed of hollowunits with cores filled with loose fill material and/or grout. Thisconstruction method provides the minimum wall thickness,while allowing insulation and reinforcement to be included toincrease thermal and structural performance, respectively.

Determining the thermal insulation values of thesewalls, however, can be time consuming, especially when thewall is composed of several materials. This TEK facilitatesthe determination of thermal resistance (R) and thermaltransmittance (U) of these single wythe concrete masonry walls.

R-VALUE TABLES

Tables of calculated R-values for hollow block of 6, 8, 10and 12 in. (152, 203, 254, and 305 mm) thicknesses, forconcrete densities of 85 to 135 lb/ft3 (1362 to 2163 kg/m3) areincluded. In addition, Table 1 shows the approximate per-centage of grouted and ungrouted wall area for differentvertical and horizontal grout spacings, which can be used todetermine R-values of partially grouted walls. Thermal prop-erties used in compiling the tables are listed in Table 6.

In addition to the core insulations listed in Tables 2through 5, polystyrene inserts are available which fit in thecores of concrete masonry units. Inserts are available in manyshapes and sizes to provide a range of insulating values andaccommodate various construction conditions. Specially de-signed concrete masonry units may incorporate reduced-height webs to accommodate inserts. Such webs also reducethermal bridging through masonry, since the reduced webarea provides a smaller cross-sectional area for heat flowthrough the wall. To further reduce thermal bridging, somemanufacturers have developed units with two cross webs ratherthan three. In addition, some inserts have building code ap-proval to be left in the grouted cores, thus improving the thermalperformance of fully or partially grouted masonry walls.

The ASHRAE series-parallel method (also called iso-thermal planes) (ref. 1) was used to calculate the base casevalues (i.e., the row Exposed block, both sides) in Tables 2through 5. This method accounts for the thermal bridging

Keywords: insulation, reinforced concrete masonry, R-values, thermal insulation, thermal properties

Table 2—R-Values For 6 in. (152 mm) Concrete Masonry Walls, hr.ft2.oF/Btua

Cores filled withb:Density Cores Loose-fill insulation Polyurethane

of concrete, empty Perlite Vermiculite foamed insulation Solid groutedConstruction pcf range mid range mid range mid range mid range midExposed block, 85 2.2-2.5 2.4 4.8-6.1 5.3 4.5-5.6 5.0 5.2-7.0 5.9 1.6-1.8 1.7 both sides 95 2.1-2.4 2.2 4.1-5.4 4.6 3.9-5.0 4.3 4.4-6.1 5.0 1.5-1.7 1.6

105 2.0-2.2 2.1 3.5-4.8 4.0 3.3-4.5 3.8 3.7-5.2 4.3 1.4-1.6 1.5115 1.8-2.1 2.0 3.0-4.2 3.4 2.9-4.0 3.3 3.1-4.5 3.6 1.4-1.5 1.4125 1.7-2.0 1.8 2.5-3.7 3.0 2.5-3.5 2.9 2.6-3.9 3.1 1.3-1.5 1.4135 1.6-1.9 1.7 2.2-3.2 2.6 2.2-3.1 2.5 2.2-3.4 2.7 1.3-1.4 1.3

1/2 in. (13 mm) 85 3.6-3.9 3.8 6.2-7.5 6.7 5.9-7.0 6.3 6.6-8.4 7.3 3.0-3.2 3.1gypsum board 95 3.5-3.8 3.6 5.5-6.8 6.0 5.3-6.4 5.7 5.8-7.5 6.4 2.9-3.1 3.0on furring 105 3.4-3.6 3.5 4.9-6.2 5.4 4.7-5.9 5.2 5.1-6.6 5.7 2.8-3.0 2.9

115 3.2-3.5 3.4 4.4-5.6 4.8 4.3-5.4 4.7 4.5-5.9 5.0 2.8-2.9 2.8125 3.1-3.4 3.2 3.9-5.1 4.4 3.9-4.9 4.3 4.0-5.3 4.5 2.7-2.9 2.8135 3.0-3.3 3.1 3.6-4.6 4.0 3.6-4.5 3.9 3.6-4.8 4.1 2.7-2.8 2.7

1 in. (25 mm) 85 7.6-7.9 7.8 10.2-11.5 10.7 9.9-11.0 10.3 10.6-12.4 11.3 7.0-7.2 7.1expanded 95 7.5-7.8 7.6 9.5-10.8 10.0 9.3-10.4 9.7 9.8-11.5 10.4 6.9-7.1 7.0polystyrenec 105 7.4-7.6 7.5 8.9-10.2 9.4 8.7-9.9 9.2 9.1-10.6 9.7 6.8-7.0 6.9

115 7.2-7.5 7.4 8.4-9.6 8.8 8.3-9.4 8.7 8.5-9.9 9.0 6.8-6.9 6.8125 7.1-7.4 7.2 7.9-9.1 8.4 7.9-8.9 8.3 8.0-9.3 8.5 6.7-6.9 6.8135 7.0-7.3 7.1 7.6-8.6 8.0 7.6-8.5 7.9 7.6-8.8 8.1 6.7-6.8 6.7

1 in. (25 mm) 85 8.6-8.9 8.8 11.2-12.5 11.7 10.9-12.0 11.3 11.6-13.4 12.3 8.0-8.2 8.1extruded 95 8.5-8.8 8.6 10.5-11.8 11.0 10.3-11.4 10.7 10.8-12.5 11.4 7.9-8.1 8.0polystyrenec 105 8.4-8.6 8.5 9.9-11.2 10.4 9.7-10.9 10.2 10.1-11.6 10.7 7.8-8.0 7.9

115 8.2-8.5 8.4 9.4-10.6 9.8 9.3-10.4 9.7 9.5-10.9 10.0 7.8-7.9 7.8125 8.1-8.4 8.2 8.9-10.1 9.4 8.9-9.9 9.3 9.0-10.3 9.5 7.7-7.9 7.8135 8.0-8.3 8.1 8.6-9.6 9.0 8.6-9.5 8.9 8.6-9.8 9.1 7.7-7.8 7.7

1 in. (25 mm) 85 12.1-12.4 12.2 14.6-16.0 15.2 14.3-15.5 14.8 15.1-16.9 15.8 11.5-11.7 11.6polyiso- 95 12.0-12.2 12.1 13.9-15.3 14.5 13.7-14.9 14.2 14.2-15.9 14.9 11.4-11.6 11.5cyanurated 105 11.8-12.1 12.0 13.3-14.6 13.8 13.2-14.3 13.7 13.5-15.1 14.1 11.3-11.5 11.4

115 11.7-12.0 11.8 12.8-14.1 13.3 12.7-13.8 13.2 12.9-14.4 13.5 11.2-11.4 11.3125 11.6-11.9 11.7 12.4-13.5 12.8 12.3-13.4 12.7 12.5-13.8 13.0 11.2-11.3 11.2135 11.5-11.8 11.6 12.1-13.1 12.4 12.0-13.0 12.4 12.0-13.2 12.5 11.1-11.3 11.2

2 x 4 furring 85 13.0-13.3 13.2 15.6-16.9 16.1 15.3-16.4 15.7 16.0-17.8 16.7 12.4-12.6 12.5with R13 batt 95 12.9-13.2 13.0 14.9-16.2 15.4 14.7-15.8 15.1 15.2-16.9 15.8 12.3-12.5 12.4& 1/2 in. (13 mm) 105 12.8-13.0 12.9 14.3-15.6 14.8 14.1-15.3 14.6 14.5-16.0 15.1 12.2-12.4 12.3gypsum board 115 12.6-12.9 12.8 13.8-15.0 14.2 13.7-14.8 14.1 13.9-15.3 14.4 12.2-12.3 12.2on furring 125 12.5-12.8 12.6 13.3-14.5 13.8 13.3-14.3 13.7 13.4-14.7 13.9 12.1-12.3 12.2

135 12.4-12.7 12.5 13.0-14.0 13.4 13.0-13.9 13.3 13.0-14.2 13.5 12.1-12.2 12.1

a Notes: (hr.ft2.oF/Btu) (0.176) = m2.K/W. Mortar joints are 3/8 in. (10 mm) thick, with face shell mortar bedding assumed. Unit dimen-sions based on Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90 (ref. 2). Surface air films are included.

b Values apply when all masonry cores are filled completely. Grout density is 140 pcf (2243 kg/m3). Lightweight grouts, which willprovide higher R-values, are also available in some areas.

c Installed over wood furring.Includes 1/2 in. (13 mm) gypsum board and nonreflective air space.d Installed over wood furring.Includes 1/2 in. (13 mm) gypsum board and reflective air space.



of concrete, empty Perlite Vermiculite foamed insulation Solid groutedConstruction pcf range mid range mid range mid range mid range midExposed block, 85 2.4-2.7 2.5 6.3-8.2 7.1 5.9-7.5 6.6 6.9-9.4 8.0 1.9-2.1 2.0 both sides 95 2.3-2.6 2.4 5.3-7.2 6.1 5.0-6.7 5.7 5.8-8.1 6.7 1.7-2.0 1.8

105 2.1-2.4 2.2 4.5-6.3 5.2 4.3-5.9 4.9 4.8-7.0 5.6 1.6-1.9 1.7115 2.0-2.3 2.1 3.8-5.5 4.4 3.7-5.2 4.3 4.0-6.0 4.7 1.5-1.8 1.6125 1.9-2.2 2.0 3.2-4.8 3.8 3.1-4.6 3.7 3.3-5.1 4.0 1.5-1.7 1.5135 1.7-2.1 1.9 2.7-4.2 3.3 2.7-4.0 3.2 2.8-4.4 3.4 1.4-1.6 1.5


115 3.4-3.7 3.5 5.2-6.9 5.8 5.1-6.6 5.7 5.4-7.4 6.1 2.9-3.2 3.0125 3.3-3.6 3.4 4.6-6.2 5.2 4.5-6.0 5.1 4.7-6.5 5.4 2.9-3.1 2.9135 3.1-3.5 3.3 4.1-5.6 4.7 4.1-5.4 4.6 4.2-5.8 4.8 2.8-3.0 2.9


115 7.4-7.7 7.5 9.2-10.9 9.8 9.1-10.6 9.7 9.4-11.4 10.1 6.9-7.2 7.0125 7.3-7.6 7.4 8.6-10.2 9.2 8.5-10.0 9.1 8.7-10.5 9.4 6.9-7.1 6.9135 7.1-7.5 7.3 8.1-9.6 8.7 8.1-9.4 8.6 8.2-9.8 8.8 6.8-7.0 6.9


115 8.4-8.7 8.5 10.2-11.9 10.8 10.1-11.6 10.7 10.4-12.4 11.1 7.9-8.2 8.0125 8.3-8.6 8.4 9.6-11.2 10.2 9.5-11.0 10.1 9.7-11.5 10.4 7.9-8.1 7.9135 8.1-8.5 8.3 9.1-10.6 9.7 9.1-10.4 9.6 9.2-10.8 9.8 7.8-8.0 7.9


115 11.9-12.2 12.0 13.7-15.4 14.3 13.5-15.1 14.1 13.8-15.8 14.6 11.4-11.6 11.5125 11.7-12.0 11.9 13.1-14.7 13.7 13.0-14.4 13.5 13.2-15.0 13.9 11.3-11.5 11.4135 11.6-11.9 11.7 12.6-14.0 13.1 12.5-13.9 13.0 12.7-14.3 13.2 11.3-11.5 11.4

2 x 4 furring 85 13.2-13.5 13.3 17.1-19.0 17.9 16.7-18.3 17.4 17.7-20.2 18.8 12.7-12.9 12.8with R13 batt & 95 13.1-13.4 13.2 16.1-18.0 16.9 15.8-17.5 16.5 16.6-18.9 17.5 12.5-12.8 12.61/2 in. (13 mm) 105 12.9-13.2 13.0 15.3-17.1 16.0 15.1-16.7 15.7 15.6-17.8 16.4 12.4-12.7 12.5gypsum board 115 12.8-13.1 12.9 14.6-16.3 15.2 14.5-16.0 15.1 14.8-16.8 15.5 12.3-12.6 12.4on furring 125 12.7-13.0 12.8 14.0-15.6 14.6 13.9-15.4 14.5 14.1-15.9 14.8 12.3-12.5 12.3

135 12.5-12.9 12.7 13.5-15.0 14.1 13.5-14.8 14.0 13.6-15.2 14.2 12.2-12.4 12.3

a Notes: (hr.ft2.oF/Btu) (0.176) = m2.K/W. Mortar joints are 3/8 in. (10 mm) thick, with face shell mortar bedding assumed. Unit dimensionsbased on Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90 (ref. 2). Surface air films are included.


c Installed over wood furring. Includes 1/2 in. (13 mm) gypsum board and nonreflective air space.d Installed over wood furring.Includes 1/2 in. (13 mm) gypsum board and reflective air space.



of concrete, Empty Perlite Vermiculite foamed insulation Solid groutedConstruction pcf range mid range mid range mid range mid range midExposed block, 85 2.5-2.9 2.7 7.5-9.9 8.5 7.0-9.1 7.9 8.2-11.3 9.5 2.1-2.4 2.2 both sides 95 2.4-2.7 2.5 6.3-8.7 7.2 6.0-8.0 6.8 6.7-9.7 7.9 1.9-2.2 2.0

105 2.2-2.5 2.3 5.2-7.5 6.1 5.0-7.0 5.8 5.5-8.2 6.6 1.8-2.1 1.9115 2.1-2.4 2.2 4.4-6.5 5.2 4.2-6.2 5.0 4.6-7.0 5.5 1.7-2.0 1.8125 1.9-2.3 2.1 3.7-5.6 4.4 3.6-5.4 4.3 3.8-6.0 4.6 1.6-1.9 1.7135 1.8-2.1 2.0 3.1-4.9 3.7 3.0-4.7 3.6 3.2-5.1 3.9 1.5-1.8 1.6


115 3.5-3.8 3.6 5.8-7.9 6.6 5.6-7.6 6.4 6.0-8.4 6.9 3.1-3.4 3.2125 3.3-3.7 3.5 5.1-7.0 5.8 5.0-6.8 5.7 5.2-7.4 6.0 3.0-3.3 3.1135 3.2-3.5 3.4 4.5-6.3 5.1 4.4-6.1 5.0 4.6-6.5 5.3 2.9-3.2 3.0


115 7.5-7.8 7.6 9.8-11.9 10.6 9.6-11.6 10.4 10.0-12.4 10.9 7.1-7.4 7.2125 7.3-7.7 7.5 9.1-11.0 9.8 9.0-10.8 9.7 9.2-11.4 10.0 7.0-7.3 7.1135 7.2-7.5 7.4 8.5-10.3 9.1 8.4-10.1 9.0 8.6-10.5 9.3 6.9-7.2 7.0


115 8.5-8.8 8.6 10.8-12.9 11.6 10.6-12.6 11.4 11.0-13.4 11.9 8.1-8.4 8.2125 8.3-8.7 8.5 10.1-12.0 10.8 10.0-11.8 10.7 10.2-12.4 11.0 8.0-8.3 8.1135 8.2-8.5 8.4 9.5-11.3 10.1 9.4-11.1 10.0 9.6-11.5 10.3 7.9-8.2 8.0


115 11.9-12.3 12.1 14.3-16.4 15.1 14.1-16.0 14.9 14.4-16.9 15.4 11.6-11.8 11.7125 11.8-12.1 11.9 13.5-15.5 14.3 13.5-15.2 14.1 13.7-15.9 14.5 11.5-11.7 11.6135 11.7-12.0 11.8 13.0-14.7 13.6 12.9-14.6 13.5 13.0-14.9 13.7 11.4-11.6 11.5


135 12.6-12.9 12.8 13.9-15.7 14.5 13.8-15.5 14.4 14.0-15.9 14.7 12.3-12.6 12.4

a Notes: (hr.ft2.oF/Btu) (0.176) = m2.K/W. Mortar joints are 3/8 in. (10 mm) thick, with face shell mortar bedding assumed. Unit dimen-sions based on Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90 (ref. 2). Surface air films are included.





of concrete, Empty Perlite Vermiculite foamed insulation Solid groutedConstruction pcf range mid range mid range mid range mid range midExposed block, 85 2.6-3.0 2.8 9.1-12.1 10.3 8.5-11.0 9.6 10.0-13.8 11.5 2.3-2.6 2.4 both sides 95 2.4-2.8 2.6 7.6-10.5 8.8 7.2-9.7 8.2 8.2-11.8 9.6 2.1-2.4 2.3

105 2.3-2.6 2.4 6.3-9.1 7.4 6.0-8.5 7.0 6.7-10.0 8.0 2.0-2.3 2.1115 2.1-2.5 2.3 5.2-7.9 6.2 5.1-7.4 6.0 5.5-8.5 6.6 1.9-2.2 2.0125 2.0-2.3 2.2 4.4-6.8 5.3 4.2-6.5 5.1 4.5-7.2 5.5 1.8-2.0 1.9135 1.9-2.2 2.0 3.6-5.8 4.4 3.6-5.6 4.3 3.7-6.1 4.6 1.7-1.9 1.8


115 3.5-3.9 3.7 6.6-9.3 7.6 6.5-8.8 7.4 6.9-9.9 8.0 3.3-3.6 3.4125 3.4-3.7 3.6 5.8-8.2 6.7 5.6-7.9 6.5 5.9-8.6 6.9 3.2-3.4 3.3135 3.3-3.6 3.4 5.0-7.2 5.8 5.0-7.0 5.7 5.1-7.5 6.0 3.1-3.3 3.2


115 7.5-7.9 7.7 10.6-13.3 11.6 10.5-12.8 11.4 10.9-13.9 12.0 7.3-7.6 7.4125 7.4-7.7 7.6 9.8-12.2 10.7 9.6-11.9 10.5 9.9-12.6 10.9 7.2-7.4 7.3135 7.3-7.6 7.4 9.0-11.2 9.8 9.0-11.0 9.7 9.1-11.5 10.0 7.1-7.3 7.2


115 8.5-8.9 8.7 11.6-14.3 12.6 11.5-13.8 12.4 11.9-14.9 13.0 8.3-8.6 8.4125 8.4-8.7 8.6 10.8-13.2 11.7 10.6-12.9 11.5 10.9-13.6 11.9 8.2-8.4 8.3135 8.3-8.6 8.4 10.0-12.2 10.8 10.0-12.0 10.7 10.1-12.5 11.0 8.1-8.4 8.2


115 12.0-12.3 12.1 15.1-17.7 16.1 14.9-17.3 15.8 15.3-18.4 16.5 11.8-12.0 11.9125 11.9-12.2 12.0 14.2-16.6 15.1 14.1-16.3 14.9 14.4-17.1 15.4 11.7-11.9 11.8135 11.8-12.1 11.9 13.5-15.7 14.3 13.4-15.5 14.2 13.6-16.0 14.5 11.6-11.8 11.7


135 12.7-13.0 12.8 14.4-16.6 15.2 14.4-16.4 15.1 14.5-16.9 15.4 12.5-12.7 12.6

a Notes: (hr.ft2.oF/Btu) (0.176) = m2.K/W. Mortar joints are 3/8 in. (10 mm) thick, with face shell mortar bedding assumed. Unit dimensionsbased on Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90 (ref. 2). Surface air films are included.



NATIONAL CONCRETE MASONRY ASSOCIATION2302 Horse Pen Road, Herndon, Virginia 22071-3499


The values for insulated and grouted cores in Tables 1through 5 are based on the assumption that all masonry coresare either insulated or grouted. That is, for walls which areeither not grouted or are fully grouted, the values in Tables 2through 5 can be used directly.

R-VALUES FOR PARTIALLY GROUTED MASONRY

For partially grouted walls, the values in Tables 2 through5 must be modified. The first step is to determine how muchof the wall area is grouted, from Table 1. The U-factor of thewall is calculated from the area-weighted average of the U-factor of the grouted area and the U-factor of the ungroutedarea as follows:

U = (agr

x Ugr

) + (aungr

x Uungr

)and R = 1/Uwhere:a

gr= fractional grouted area of wall

aungr

= fractional ungrouted area of wallR = total thermal resistance of wall, hr.ft2.oF/Btu (m2.K/W)U = total thermal conductance of wall, Btu/hr·ft2·oF (W/

m2.K)U

gr= conductance of fully grouted wall, Btu/hr·ft2·oF (W/

m2.K)U

ungr= conductance of ungrouted wall, Btu/hr·ft2·oF (W/m2.K)

For example, consider an 8 in. (203 mm) wall composedof hollow 105 lb/ft3 (1682 kg/m3) concrete masonry, and groutedat 48 in. (1219 mm) o.c. both vertically and horizontally. Theungrouted cores contain perlite loose fill insulation.

From Table 1, 31% of the wall is grouted and 69%contains insulation. From Table 3, the R-value for a solidlygrouted concrete masonry wall is 1.7 hr.ft2.oF/Btu (0.30 m2.K/W). The corresponding U-factor is 1/1.7 or 0.588 Btu/hr.ft2.oF(3.3 W/m2.K). Again from Table 3, a wall containing perliteloose fill insulation has an R-value of 5.2, with a correspond-ing U-factor of 0.192. The U-factor and R-value of the wall arecalculated as follows:

U = agr x Ugr + aungr x Uungr

= (0.31 x 0.588) + (0.69 x 0.192)= 0.315 Btu/hr·ft2·oF (1.79 W/m2.K)

R = 1/U = 1/0.315 = 3.2 hr·ft2·oF/Btu (0.56 m2.K/W)

Table 6—Thermal Data Used to Develop Tables

Thermal resistivity(R-value per inch),

Material: hr.ft2.oF/Btu.in (m.K/W)Vermiculite 2.27 (15.7)Perlite 3.13 (21.7)Expanded polystyrene 4.00 (27.7)Extruded polystyrene 5.00 (34.7)Cellular polyisocyanurate, gas-impermeable facer 7.04 (48.8)Polyurethane foamed-in-place insulation 5.91 (41.0)Wood 1.00 (6.9)Concrete:

85 pcf 0.23-0.34 (1.6-2.4)95 pcf 0.18-0.28 (1.2-1.9)105 pcf 0.14-0.23 (0.97-1.6)115 pcf 0.11-0.19 (0.76-1.3)125 pcf 0.08-0.15 (0.55-1.0)135 pcf 0.07-0.12 (0.49-0.83)140 pcf 0.06-0.11 (0.40-0.78)

Mortar 0.20 (1.4)

R-value, hr.ft2.oF/BtuMaterial (m2.K/W)1/2 in. (13 mm) gypsum wallboard 0.45 (0.08)Inside surface air film 0.68 (0.12)Outside surface air film 0.17 (0.03)Nonreflective air space 0.97 (0.17)Reflective air space 2.38 (0.42)

REFERENCES1. ASHRAE Fundamentals Handbook. Atlanta, GA: Ameri-

can Society of Heating, Refrigerating and Air-Condition-ing Engineers, Inc., 1993.

2. Standard Specification for Loadbearing Concrete Ma-sonry Units, ASTM C 90-95. American Society for Test-ing and Materials, 1995.

3. Valore, Rudolph C. The Thermophysical Properties ofMasonry and Its Constituents, Parts I and II. Washington,DC: International Masonry Institute, 1988.

FIRE RESISTANCE RATING OF TEK 7-1ACONCRETE MASONRY ASSEMBLIES

Keywords: columns, control joints, equivalent thickness,fire resistance ratings, fire walls, multi-wythe walls, speci-fications

INTRODUCTION

This TEK conforms to the stated parameters of theStandard Method for Determining Fire Resistance of Con-crete and Masonry Construction Assemblies, ACI 216.1-97/TMS 0216.1-97 (ref. 1–hereinafter referred to as the Stan-dard). Concrete masonry is widely specified for fire walls andfire separation walls because these elements are:

∑ noncombustible,∑ provide durable fire resistance, and∑ are economical to construct.For the most part, the contents of the Standard are not

new, but rather are a compilation and refinement of the manydocuments previously published by the various segments ofthe masonry and concrete industry. More importantly, theStandard is a document that has gone through a formalconsensus process and is written in mandatory language, andtherefore is now incorporated by reference into the nationalmodel codes.

Methods of Determining Fire Resistance RatingsThe fire resistance rating period of concrete masonry

elements can be determined by three methods:∑ calculation,∑ through a listing service, or∑ by testing.The calculation method is the most practical and most

commonly used method of determining the fire resistancerating of concrete masonry. It is based on extensive researchwhich established a relationship between physical propertiesof materials and the fire resistance rating. The calculationmethod is utilized in the Standard which determines fireresistance ratings based on the equivalent thickness of con-crete masonry units and aggregate types used in their manu-facture.

An alternative to the calculation method is provided byprivate commercial listing services. The listing serviceapproach allows the designer to select a fire rated assemblywhich has been previously classified and listed in a published

Fire Resistance (2001)


TEK 7-1A © 2001 National Concrete Masonry Association (replaces TEK 7-1 and 7-3)

directory of listed fire rated assemblies. The listing servicealso monitors materials and production to verify that theconcrete masonry units are and remain in compliance withappropriate standards. A premium is usually charged forunits of this type. The system also is somewhat inflexible inthat little variation from the original tested wall assembly isallowed including unit size, shape, mix design, ingredients,and even the plant of manufacture.

The third option, testing of representative elements of theconstruction in accordance with standard fire test methods isgenerally not practical due to the expense of the test and timerequired to build, cure, and test representative specimens.

CALCULATED FIRE RESISTANCE METHOD

ScopeThis TEK covers methods for determining the fire resis-

tance rating of concrete masonry assemblies, including walls,columns, lintels, beams, and concrete masonry fire protectionfor steel columns. It also includes assemblies composed ofconcrete masonry and other components including plasterand drywall finishes, and multi-wythe masonry componentsincluding clay or shale masonry units.

BackgroundThe calculated fire resistance method is based on exten-

sive research and results of previous testing of concretemasonry walls. Fire testing of wall assemblies is conductedin accordance with the Standard Test Methods for Fire Testsof Building Construction and Materials, ASTM E 119 (ref. 7)which measures four performance criteria.ASTM E 119 Performance Criteria:

∑ resistance to the transmission of heat through thewall assembly,

∑ resistance to the passage of hot gases through thewall sufficient to ignite cotton waste,

∑ load carrying capacity of loadbearing walls, and∑ resistance to the impact, erosion, and cooling effects

of a hose stream on the assembly after exposure tothe standard fire.

The fire resistance rating of concrete masonry is typicallygoverned by the heat transmission criteria. This type offailure mode is certainly preferable to a structural collapseendpoint characteristic of many other building materialsfrom the standpoint of life safety (particularly for fire fighters)

and salvageability.Fire testing of concrete masonry columns evaluates the

ability of the column to carry design loads under standard firetest conditions. Fire testing of a concrete masonry protectedsteel column assembly evaluates the structural integrity of thesteel column under fire test conditions by measuring thetemperature rise of the steel.

Fire testing of concrete masonry beams and lintels evalu-ates the ability of the member to sustain design loads understandard fire test conditions. This is accomplished by insur-ing that the temperature rise of the tensile reinforcing doesnot exceed 1100 oF (593 oC) during the rating period.

Equivalent ThicknessExtensive testing has established a relationship between

the fire resistance and the equivalent solid thickness forconcrete masonry walls as shown in Table 1. Equivalentthickness is essentially the solid thickness that would beobtained if the same amount of masonry contained in a hollowunit were recast without core holes. The equivalent thicknessof a hollow unit is equal to the percentage solid times theactual thickness of the unit. See Figure 1. The percentagesolid is determined in accordance with Standard Methods ofSampling and Testing Concrete Masonry Units, ASTM C140 (ref. 2).

The equivalent thickness of a 100% solid unit or a solidgrouted unit is equal to the actual thickness. For partiallygrouted walls where the unfilled cells are left empty, theequivalent thickness for fire resistance rating purposes is

equal to that of an ungrouted unit.Loadbearing units conforming to ASTM C 90 (ref. 6)

that are commonly available include 100% solid units, 75%solid units, and hollow units meeting minimum requiredfaceshell and web dimensions. Typical equivalent thicknessvalues for these units are listed in Table 2.

Filling Cells with Loose Fill MaterialIf the cells of hollow unit masonry are filled with

approved materials, the equivalent thickness of the assemblycan be considered the same as the actual thickness. The listof approved materials includes: sand, pea gravel, crushedstone, or slag that meets ASTM C 33 (ref. 3) requirements;pumice, scoria, expanded shale, expanded clay, expandedslate, expanded slag, expanded flyash, or cinders that complywith ASTM C 331 (ref. 4) or C 332 (ref. 5), or perlite orvermiculite meeting the requirements of ASTM C 549 and C516 (refs. 9 and 8), respectively.

Wall AssembliesThe fire resistance rating is determined in accordance

with Table 1 utilizing the appropriate aggregate type of themasonry unit and the equivalent thickness. Units manufac-tured with a combination of aggregate types are addressed byfootnote (2) which may be expressed by the following equa-tion:

If this hollowunit is 53% solid,

the equivalentthickness is4.04 inches

7 5/8" 4.04"

Equivalent Thickness = 0.53 x 7-5/8 in. = 4.04 in.

Figure 1—Equivalent Thickness Calculation

Table 2—Equivalent Thickness of ConcreteMasonry Units, in. (mm)

Nominal Based on Based onwidth, in. typical percent solid

(mm) hollow units1 (75%) (100%)

4 (102) 2.7 (69) [73.8] 2.7 (69) 3.6 (91)6 (152) 3.1 (79) [55.0] 4.2 (107) 5.6 (142)8 (203) 4.0(102) [53.0] 5.7 (145) 7.6 (193)

10 (254) 5.0(127) [51.7] 7.2 (183) 9.6 (244)12 (305) 5.7(145) [48.7] 8.7 (221) 11.6 (295)

1. Values in brackets [ ] are percent solid values basedon typical two core concrete masonry units.

Table 1—Fire Resistance Rating Period of Concrete Masonry Assemblies (ref. 1)

Aggregate type in the Minimum required equivalent thickness for fire resistance rating, in. (mm)1

concrete masonry unit2 4 hours 3 hours 2 hours 1.5 hours 1 hour 0.75 hours 0.5 hoursCalcareous or siliceous gravel 6.2 (157) 5.3 (135) 4.2 (107) 3.6 (91) 2.8 (71) 2.4 (61) 2.0 (51)Limestone, cinders or slag 5.9 (150) 5.0 (127) 4.0 (102) 3.4 (86) 2.7 (69) 2.3 (58) 1.9 (48)Expanded clay, shale or slate 5.1 (130) 4.4 (112) 3.6 (91) 3.3 (84) 2.6 (66) 2.2 (56) 1.8 (46)Expanded slag or pumice 4.7 (119) 4.0 (102) 3.2 (81) 2.7 (69) 2.1 (53) 1.9 (48) 1.5 (38)

1. Fire resistance rating between the hourly fire resistance rating periods listed may be determined by linear interpolation based on theequivalent thickness value of the concrete masonry assembly.

2. Minimum required equivalent thickness corresponding to the hourly fire resistance rating for units made with a combination of aggregatesshall be determined by linear interpolation based on the percent by volume of each aggregate used in the manufacture.

Figure 2—Fire Resistance of Multi-WytheMasonry Wall (ref. 1)

Wythe (R2) Air space factor (A1) forwidths 1/2 in. (13 mm) orgreater

Wythe (R1)

R1 = Fire resistance rating of wythe 1R2 = Fire resistance rating of wythe 2A1 = Air space factor = 0.3

Table 3—Fire Resistance of Brick or Tile

of Clay or Shale (ref.1)

Material type

Minimum required equivalent thickness1 for

fire resistance rating, in. (mm)

4 hours 3 hours 2 hours l hour

> 75% solid

Hollow units2

Hollow units3

6.0 (152)

5.0 (127)

6.6 (168)

4.9 (124)

4.3 (109)

5.5 (140)

3.8 (97)

3.4 (86)

4.4 (112)

2.7 (69)

2.3 (58)

3.0 (76)

1. See section entitled "Equivalent Thickness" for calculation.2. Unfilled hollow units.3. Grouted or filled per section entitled "Filling Cells with Loose Fill Material".

For multi-wythe walls of clay brick and concrete ma-sonry, use the values of Table 3 for the brick wythe in theabove equation.

Concrete Masonry LintelsThe fire resistance rating of concrete masonry lintels is

determined based upon the nominal thickness of the linteland the minimum cover of longitudinal reinforcement inaccordance with Table 5. Cover requirements in excess of 1½in. (38 mm) protect the reinforcement from strength degra-dation due to excessive temperature during the fire exposureperiod. Cover requirements may be provided by masonryunits, grout, or mortar.

Tr = (T1 x V1) + (T2 x V2)

Where:Tr = required equivalent thickness for a specific fire

resistance rating of an assembly constructed ofunits with combined aggregates, in. (mm)

T1, T2 = required equivalent thickness for a specific fireresistance rating of a wall constructed of units withaggregate types 1 and 2, respectively, in. (mm)

V1, V2= fractional volume of aggregate types 1 and 2, re-spectively, used in the manufacture of the unit

Multi-Wythe Wall AssembliesThe fire resistance rating of multi-wythe walls (Figure 2) isbased on the fire resistance of each wythe and the air spacebetween each wythe in accordance with the following Equa-tion.

R = (R10.59 + R2

0.59 +...+Rn0.59 + A1 + A2 +... An)

1.7

Where:R1, R2,...Rn = fire resistance rating of wythe 1, 2,...n,

respectively (hours).A1, A2,...An = 0.30; factor for each air space, 1, 2,...n,

respectively, having a width of 1/2 to 31/2 in. (13 to 89 mm)between wythes. Note: It does not matter which side isexposed to the fire.

Reinforced Concrete Masonry ColumnsThe fire resistance rating of reinforced concrete masonry

columns is based on the least plan dimension of the columnas indicated in Table 4. The minimum required cover over thevertical reinforcement is 2 in. (51 mm).

Table 5—Reinforced Concrete Masonry LintelsMinimum Longitudinal Reinforcing Cover,

in. (mm) (ref. 1)Nominal

lintel width, Fire resistance ratingin., (mm) 1 hour 2 hours 3 hours 4 hours6 (152) 11/2 (38) 2 (51) - -8 (203) 11/2 (38) 11/2 (38) 13/4 (44) 3 (76)

10 (254) or more 11/2 (38) 11/2 (38) 11/2 (38) 13/4(44)

Blended aggregate example:The required equivalent thickness of an assembly

constructed of units made with expanded shale (80% byvolume), and calcareous sand (20% by volume), to meet a3 hour fire resistance rating is:

T1 for expanded shale (3 hour rating) = 4.4 in. (112 mm)T2 for calcareous sand (3 hour rating) = 5.3 in. (135 mm)Tr = (4.4 x 0.80) + (5.3 x 0.20) = 4.58 in. (116 mm)

Table 4—Reinforced Concrete Masonry Columns (ref. 1)

Minimum column dimensions, in. (mm),for fire resistance rating of:

1 hour 2 hours 3 hours 4 hours

8 (203) 10 (254) 12 (305) 14 (356)

Control JointsFigure 3 shows control joint details in fire rated wall

assemblies in which openings are not permitted or whereopenings are required to be protected. Maximum joint widthis ½ in. (13 mm).

Steel Columns Protected by Concrete MasonryThe fire resistance rating of steel columns protected by

concrete masonry as illustrated in Figure 4 is determined bythe following equation:

R = 0.401(Ast /ps)0.7 + {0.285(Tea

1.6/k 0.2) x[1.0 + (42.7{(Ast/DTea)/(0.25p + Tea)}

0.8 )]}(English units)R = 7.13(Ast ps)

0.7 + {0.0027(Tea1.6/k 0.2) x

[1.0 + (2.49x107{(Ast/DTea)/(0.25p + Tea)}0.8 )]}(SI units)

Where:R = Fire resistance rating of the column assembly, hr.Ast = Cross-sectional area of the steel column, in.2 (m2)D = Density of concrete masonry protection, pcf (kg/m3) ps = Heated perimeter of steel column, in. (mm)k = Thermal conductivity of concrete masonry, Table 6,

Btu/hr•ft•oF (W/m•K)p = Inner perimeter of concrete masonry protection, in. (mm)Tea = Equivalent thickness of concrete masonry protec-

tion, in. (mm)

Table 6—Properties of Concrete Masonry Units

Density, D Thermal conductivity1, kpcf (kg/m3) Btu/hr•ft•oF (W/m•K)

80 (1281) 0.207 (0.358)85 (1362) 0.228 (0.394)90 (1442) 0.252 (0.436)95 (1522) 0.278 (0.481)

100 (1602) 0.308 (0.533)105 (1682) 0.340 (0.588)110 (1762) 0.376 (0.650)115 (1842) 0.416 (0.720)120 (1922) 0.459 (0.749)125 (2002) 0.508 (0.879)130 (2082) 0.561 (0.971)135 (2162) 0.620 (1.073)140 (2243) 0.685 (1.186)145 (2323) 0.758 (1.312)150 (2403) 0.837 (1.449)

1. Thermal conductivity at 70 oF. oC = (oF-32)(5/9)

Effects of Finish MaterialsIn many cases drywall, plaster or stucco finishes are

added to concrete masonry walls. While finishes are nor-mally applied for architectural reasons, they also provideadditional fire resistance value. The Standard (ref. 1) makesprovision for calculating the additional fire resistance pro-vided by these finishes.

It should be noted that when finishes are used to achieve

Figure 3—Control Joints for Fire Resistant Concrete Masonry Assemblies (ref. 1)

4 Hour Fire Resistance Rating

Sealant and backerMortar (1/2 in., 13 mmminimum depth)




Sealant and backer

Preformed gasket

Sealant and backer

Bond breaker Sealant and backer

Grout key

Ceramic fiber felt(alumina-silica fibers)

Vertical reinforcementeach side of joint

the required fire resistance rating, the masonry alone mustprovide at least one-half of the total required rating. This isto assure structural integrity during a fire.

Certain finishes deteriorate more rapidly when exposedto fire than when on the non-fire side of the wall. Therefore,two separate tables are required. Table 7 applies to finisheson the non-fire exposed side of the wall and Table 8 appliesto finishes on the fire exposed side.

For finishes on the non-fire exposed side of the wall, the

Figure 4—Details of Concrete Masonry ColumnProtection for Commonly Used Shapes (ref. 1)

tweb

w

d

ps = 2(w + d) + 2(w - tweb) ps = 4d

ps = pd0.25p

0.25p

d

d finish is converted to equivalent thickness of concrete ma-sonry by multiplying the thickness of the finish by the factorgiven in Table 7. This is then added to the base concretemasonry wall equivalent thickness which is used in Table 1to determine the fire resistance rating.

For finishes on the fire exposed side of the wall, a timeis assigned to the finish in Table 8 which is added to the fireresistance rating determined for the base wall and non-fireside finish. The times listed in Table 8 are essentially thelength of time the various finishes will remain intact whenexposed to fire (on the fire side of the wall).

When calculating the fire resistance rating of a wall withfinishes, two calculations are performed. The first is assum-ing fire on one side of the wall and the second is assuming thefire on the other side. The fire rating of the wall assembly isthen the lowest of the two. Note that there may be situationswhere the wall needs to rated with the fire on only one side.

Installation of FinishesFinishes that are assumed to contribute to the total fire

resistance rating of a wall must meet certain minimuminstallation requirements. Plaster and stucco need only beapplied in accordance with the provisions of the buildingcode. Gypsum wallboard and gypsum lath may be attachedto wood or metal furring strips spaced a maximum of 24 in.(610 mm) on center or may be attached directly to the wallwith adhesives. Drywall and furring may be attached in oneof two ways:

Table 8—Time Assigned to Finish Materials onFire Exposed Side of Wall (ref. 1)

Finish description Time, min

Gypsum wallboard 3/8 in . (10 mm) 1/2 in . (13 mm) 5/8 in . (16 mm)

Two layers of 3/8 in . (10 mm) One layer of 3/8 in . (10mm) and one layer of 1/2 in . (16mm) Two layers of 1/2 in . (16 mm)

10152025

3540

Type “X” gypsum wallboard1/2 in . (13 mm)5/8 in . (16 mm)

2540

Direct-applied portland cement-sand plaster See Note 1

Portland cement-sand plaster on metal lath3/4 in . (19 mm)7/8 in . (22 mm)1 in . (25 mm)

202530

Gypsum-sand plaster on 3/8 in . (10 mm)gypsum lath

1/2 in . (13 mm)5/8 in . (16 mm)3/4 in . (22 mm)

354050

Gypsum-sand plaster on metal lath3/4 in . (19 mm)7/8 in . (22 mm)1 in . (25 mm)

506080

1. For purposes of determining the contribution of portland cement- sand plaster to the equivalent thickness of concrete or masonry for use in Table 1, i t shall be permitted to use the actual thickness of the plaster, or 5/8 in. (16 mm), whichever is smaller.

Table 7—Multiplying Factor for Finishes on Non-Fire Exposed Side of Wall (ref. 1)

Type of finishapplied to s lab

or wal l

Type of material used in concretemasonry uni ts

Sil iceous orcarbonate aggregate

concrete masonryuni t

Expanded shale ,expanded clay,

expanded slag, orpumice less than 20

percent sand

Portland cement-sand plaster1 or

terrazzo1.00 0.75

Gypsum-sandplaster

1.25 1.00

Gypsum-vermic-ulite or perlite

plaster1.75 1.25

Gypsum wal l -board

3.00 2.25

1. For port land cement-sand plaster 5/8 in . (16 mm) or less in thickness, and applied direct ly to concrete masonry on the non-fire- exposed side of the wall , mult iplying factor shall be 1.0.



1). Self-tapping drywall screws spaced a maximum of 12 in.(305 mm) and penetrating a minimum of 3/8 in. (10 mm)into resilient steel furring channels running horizontallyand spaced a maximum of 24 in. (610 mm) on center.

2). Lath nails spaced at 12 in. (305 mm) on center maxi-mum, penetrating 3/4 in. (19 mm) into nominal 1 x 2 in.(25 x 51 mm) wood furring strips which are attached tothe masonry with 2 in. (51 mm) concrete nails spaced amaximum of 16 in. (41 mm) on center.Gypsum wallboard must be installed with the long

dimension parallel to the furring members and all horizontaland vertical joints must be supported and finished. The onlyexception is 5/8 in. (16 mm) Type "X" gypsum wallboardwhich may be installed horizontally without being supportedat the horizontal joints.

For drywall attached by the adhesive method, a 3/8 in. (10mm) bead of panel adhesive must be placed around theperimeter of the wallboard and across the diagonals and thensecured with a masonry nail for each 2 ft2 (0.19 m2)of panel.

CONCLUSION

The calculated fire resistance procedure is practical,versatile, and economical. It is based on thousands of tests.It is incorporated by reference into the major model codes ofthe US and allows the designer virtually unlimited flexibilityto incorporate the excellent fire resistive properties of con-crete masonry into the design.

REFERENCES

1. Standard Method for Determining Fire Resistance of Con-crete and Masonry Construction Assemblies, ACI 216.1-97/TMS 0216.1-97. American Concrete Institute and The Ma-sonry Society, 1997.

2. Standard Methods of Sampling and Testing Concrete Ma-sonry Units, ASTM C 140-01. American Society for Testingand Materials, 2001.

3. Standard Specification for Concrete Aggregates, ASTM C33-01. American Society for Testing and Materials, 2001.

4. Standard Specification for Lightweight Aggregates for Con-crete Masonry Units, ASTM C 331-01. American Society forTesting and Materials, 2001.

5. Standard Specification for Lightweight Aggregates forInsulating Concrete, ASTM C 332-99. American Society forTesting and Materials, 1999.

6. Standard Specification for Loadbearing Concrete MasonryUnits, ASTM C 90-01. American Society for Testing andMaterials, 2001.

7. Standard Test Methods for Fire Tests of Building Construc-tion and Materials, ASTM E 119-00a. American Society forTesting and Materials, 2000.

8. Standard Specification for Vermiculite Loose Fill Insulation,ASTM C 516-80(1996)e1. American Society for Testing andMaterials, 1996.

9. Standard Specification for Perlite Loose Fill Insulation, ASTMC 549-81(1995)e1. American Society for Testing and Materials,1995.

FIRE RESISTANCE RATING OF TEK 7-1ACONCRETE MASONRY ASSEMBLIES

Keywords: columns, control joints, equivalent thickness,fire resistance ratings, fire walls, multi-wythe walls, speci-fications

INTRODUCTION

This TEK conforms to the stated parameters of theStandard Method for Determining Fire Resistance of Con-crete and Masonry Construction Assemblies, ACI 216.1-97/TMS 0216.1-97 (ref. 1–hereinafter referred to as the Stan-dard). Concrete masonry is widely specified for fire walls andfire separation walls because these elements are:

∑ noncombustible,∑ provide durable fire resistance, and∑ are economical to construct.For the most part, the contents of the Standard are not

new, but rather are a compilation and refinement of the manydocuments previously published by the various segments ofthe masonry and concrete industry. More importantly, theStandard is a document that has gone through a formalconsensus process and is written in mandatory language, andtherefore is now incorporated by reference into the nationalmodel codes.

Methods of Determining Fire Resistance RatingsThe fire resistance rating period of concrete masonry

elements can be determined by three methods:∑ calculation,∑ through a listing service, or∑ by testing.The calculation method is the most practical and most

commonly used method of determining the fire resistancerating of concrete masonry. It is based on extensive researchwhich established a relationship between physical propertiesof materials and the fire resistance rating. The calculationmethod is utilized in the Standard which determines fireresistance ratings based on the equivalent thickness of con-crete masonry units and aggregate types used in their manu-facture.

An alternative to the calculation method is provided byprivate commercial listing services. The listing serviceapproach allows the designer to select a fire rated assemblywhich has been previously classified and listed in a published

Fire Resistance (2001)


TEK 7-1A © 2001 National Concrete Masonry Association (replaces TEK 7-1 and 7-3)

directory of listed fire rated assemblies. The listing servicealso monitors materials and production to verify that theconcrete masonry units are and remain in compliance withappropriate standards. A premium is usually charged forunits of this type. The system also is somewhat inflexible inthat little variation from the original tested wall assembly isallowed including unit size, shape, mix design, ingredients,and even the plant of manufacture.

The third option, testing of representative elements of theconstruction in accordance with standard fire test methods isgenerally not practical due to the expense of the test and timerequired to build, cure, and test representative specimens.

CALCULATED FIRE RESISTANCE METHOD

ScopeThis TEK covers methods for determining the fire resis-

tance rating of concrete masonry assemblies, including walls,columns, lintels, beams, and concrete masonry fire protectionfor steel columns. It also includes assemblies composed ofconcrete masonry and other components including plasterand drywall finishes, and multi-wythe masonry componentsincluding clay or shale masonry units.

BackgroundThe calculated fire resistance method is based on exten-

sive research and results of previous testing of concretemasonry walls. Fire testing of wall assemblies is conductedin accordance with the Standard Test Methods for Fire Testsof Building Construction and Materials, ASTM E 119 (ref. 7)which measures four performance criteria.ASTM E 119 Performance Criteria:

∑ resistance to the transmission of heat through thewall assembly,

∑ resistance to the passage of hot gases through thewall sufficient to ignite cotton waste,

∑ load carrying capacity of loadbearing walls, and∑ resistance to the impact, erosion, and cooling effects

of a hose stream on the assembly after exposure tothe standard fire.

The fire resistance rating of concrete masonry is typicallygoverned by the heat transmission criteria. This type offailure mode is certainly preferable to a structural collapseendpoint characteristic of many other building materialsfrom the standpoint of life safety (particularly for fire fighters)

and salvageability.Fire testing of concrete masonry columns evaluates the

ability of the column to carry design loads under standard firetest conditions. Fire testing of a concrete masonry protectedsteel column assembly evaluates the structural integrity of thesteel column under fire test conditions by measuring thetemperature rise of the steel.

Fire testing of concrete masonry beams and lintels evalu-ates the ability of the member to sustain design loads understandard fire test conditions. This is accomplished by insur-ing that the temperature rise of the tensile reinforcing doesnot exceed 1100 oF (593 oC) during the rating period.

Equivalent ThicknessExtensive testing has established a relationship between

the fire resistance and the equivalent solid thickness forconcrete masonry walls as shown in Table 1. Equivalentthickness is essentially the solid thickness that would beobtained if the same amount of masonry contained in a hollowunit were recast without core holes. The equivalent thicknessof a hollow unit is equal to the percentage solid times theactual thickness of the unit. See Figure 1. The percentagesolid is determined in accordance with Standard Methods ofSampling and Testing Concrete Masonry Units, ASTM C140 (ref. 2).

The equivalent thickness of a 100% solid unit or a solidgrouted unit is equal to the actual thickness. For partiallygrouted walls where the unfilled cells are left empty, theequivalent thickness for fire resistance rating purposes is

equal to that of an ungrouted unit.Loadbearing units conforming to ASTM C 90 (ref. 6)

that are commonly available include 100% solid units, 75%solid units, and hollow units meeting minimum requiredfaceshell and web dimensions. Typical equivalent thicknessvalues for these units are listed in Table 2.

Filling Cells with Loose Fill MaterialIf the cells of hollow unit masonry are filled with

approved materials, the equivalent thickness of the assemblycan be considered the same as the actual thickness. The listof approved materials includes: sand, pea gravel, crushedstone, or slag that meets ASTM C 33 (ref. 3) requirements;pumice, scoria, expanded shale, expanded clay, expandedslate, expanded slag, expanded flyash, or cinders that complywith ASTM C 331 (ref. 4) or C 332 (ref. 5), or perlite orvermiculite meeting the requirements of ASTM C 549 and C516 (refs. 9 and 8), respectively.

Wall AssembliesThe fire resistance rating is determined in accordance

with Table 1 utilizing the appropriate aggregate type of themasonry unit and the equivalent thickness. Units manufac-tured with a combination of aggregate types are addressed byfootnote (2) which may be expressed by the following equa-tion:

If this hollowunit is 53% solid,

the equivalentthickness is4.04 inches

7 5/8" 4.04"

Equivalent Thickness = 0.53 x 7-5/8 in. = 4.04 in.

Figure 1—Equivalent Thickness Calculation

Table 2—Equivalent Thickness of ConcreteMasonry Units, in. (mm)

Nominal Based on Based onwidth, in. typical percent solid

(mm) hollow units1 (75%) (100%)

4 (102) 2.7 (69) [73.8] 2.7 (69) 3.6 (91)6 (152) 3.1 (79) [55.0] 4.2 (107) 5.6 (142)8 (203) 4.0(102) [53.0] 5.7 (145) 7.6 (193)

10 (254) 5.0(127) [51.7] 7.2 (183) 9.6 (244)12 (305) 5.7(145) [48.7] 8.7 (221) 11.6 (295)

1. Values in brackets [ ] are percent solid values basedon typical two core concrete masonry units.

Table 1—Fire Resistance Rating Period of Concrete Masonry Assemblies (ref. 1)

Aggregate type in the Minimum required equivalent thickness for fire resistance rating, in. (mm)1

concrete masonry unit2 4 hours 3 hours 2 hours 1.5 hours 1 hour 0.75 hours 0.5 hoursCalcareous or siliceous gravel 6.2 (157) 5.3 (135) 4.2 (107) 3.6 (91) 2.8 (71) 2.4 (61) 2.0 (51)Limestone, cinders or slag 5.9 (150) 5.0 (127) 4.0 (102) 3.4 (86) 2.7 (69) 2.3 (58) 1.9 (48)Expanded clay, shale or slate 5.1 (130) 4.4 (112) 3.6 (91) 3.3 (84) 2.6 (66) 2.2 (56) 1.8 (46)Expanded slag or pumice 4.7 (119) 4.0 (102) 3.2 (81) 2.7 (69) 2.1 (53) 1.9 (48) 1.5 (38)

1. Fire resistance rating between the hourly fire resistance rating periods listed may be determined by linear interpolation based on theequivalent thickness value of the concrete masonry assembly.

2. Minimum required equivalent thickness corresponding to the hourly fire resistance rating for units made with a combination of aggregatesshall be determined by linear interpolation based on the percent by volume of each aggregate used in the manufacture.

Figure 2—Fire Resistance of Multi-WytheMasonry Wall (ref. 1)

Wythe (R2) Air space factor (A1) forwidths 1/2 in. (13 mm) orgreater

Wythe (R1)

R1 = Fire resistance rating of wythe 1R2 = Fire resistance rating of wythe 2A1 = Air space factor = 0.3

Table 3—Fire Resistance of Brick or Tile of Clay or Shale (ref.1)

Material typeMinimum required equivalent thickness1 for

fire resistance rating, in. (mm)

4 hours 3 hours 2 hours l hour

> 75% solidHollow units2

Hollow units3

6.0 (152)5.0 (127)6.6 (168)

4.9 (124)4.3 (109)5.5 (140)

3.8 (97)3.4 (86)4.4 (112)

2.7 (69)2.3 (58)3.0 (76)

1. See section entitled "Equivalent Thickness" for calculation.2. Unfilled hollow units.3. Grouted or filled per section entitled "Filling Cells with Loose Fill Material".

For multi-wythe walls of clay brick and concrete ma-sonry, use the values of Table 3 for the brick wythe in theabove equation.

Concrete Masonry LintelsThe fire resistance rating of concrete masonry lintels is

determined based upon the nominal thickness of the linteland the minimum cover of longitudinal reinforcement inaccordance with Table 5. Cover requirements in excess of 1½in. (38 mm) protect the reinforcement from strength degra-dation due to excessive temperature during the fire exposureperiod. Cover requirements may be provided by masonryunits, grout, or mortar.

Tr = (T1 x V1) + (T2 x V2)

Where:Tr = required equivalent thickness for a specific fire

resistance rating of an assembly constructed ofunits with combined aggregates, in. (mm)

T1, T2 = required equivalent thickness for a specific fireresistance rating of a wall constructed of units withaggregate types 1 and 2, respectively, in. (mm)

V1, V2= fractional volume of aggregate types 1 and 2, re-spectively, used in the manufacture of the unit

Multi-Wythe Wall AssembliesThe fire resistance rating of multi-wythe walls (Figure 2) isbased on the fire resistance of each wythe and the air spacebetween each wythe in accordance with the following Equa-tion.

R = (R10.59 + R2

0.59 +...+Rn0.59 + A1 + A2 +... An)

1.7

Where:R1, R2,...Rn = fire resistance rating of wythe 1, 2,...n,

respectively (hours).A1, A2,...An = 0.30; factor for each air space, 1, 2,...n,

respectively, having a width of 1/2 to 31/2 in. (13 to 89 mm)between wythes. Note: It does not matter which side isexposed to the fire.

Reinforced Concrete Masonry ColumnsThe fire resistance rating of reinforced concrete masonry

columns is based on the least plan dimension of the columnas indicated in Table 4. The minimum required cover over thevertical reinforcement is 2 in. (51 mm).

Table 5—Reinforced Concrete Masonry LintelsMinimum Longitudinal Reinforcing Cover,

in. (mm) (ref. 1)Nominal

lintel width, Fire resistance ratingin., (mm) 1 hour 2 hours 3 hours 4 hours6 (152) 11/2 (38) 2 (51) - -8 (203) 11/2 (38) 11/2 (38) 13/4 (44) 3 (76)

10 (254) or more 11/2 (38) 11/2 (38) 11/2 (38) 13/4(44)

Blended aggregate example:The required equivalent thickness of an assembly

constructed of units made with expanded shale (80% byvolume), and calcareous sand (20% by volume), to meet a3 hour fire resistance rating is:

T1 for expanded shale (3 hour rating) = 4.4 in. (112 mm)T2 for calcareous sand (3 hour rating) = 5.3 in. (135 mm)Tr = (4.4 x 0.80) + (5.3 x 0.20) = 4.58 in. (116 mm)

Table 4—Reinforced Concrete Masonry Columns (ref. 1)

Minimum column dimensions, in. (mm),for fire resistance rating of:

1 hour 2 hours 3 hours 4 hours

8 (203) 10 (254) 12 (305) 14 (356)

Control JointsFigure 3 shows control joint details in fire rated wall

assemblies in which openings are not permitted or whereopenings are required to be protected. Maximum joint widthis ½ in. (13 mm).

Steel Columns Protected by Concrete MasonryThe fire resistance rating of steel columns protected by

concrete masonry as illustrated in Figure 4 is determined bythe following equation:

R = 0.401(Ast /ps)0.7 + {0.285(Tea

1.6/k0.2) x[1.0 + (42.7{(Ast/DTea)/(0.25p + Tea)}

0.8 )]}(English units)R = 7.13(Ast ps)

0.7 + {0.0027(Tea1.6/k0.2) x

[1.0 + (2.49x107{(Ast/DTea)/(0.25p + Tea)}0.8 )]}(SI units)

Where:R = Fire resistance rating of the column assembly, hr.Ast = Cross-sectional area of the steel column, in.2 (m2)D = Density of concrete masonry protection, pcf (kg/m3) ps = Heated perimeter of steel column, in. (mm)k = Thermal conductivity of concrete masonry, Table 6,

Btu/hr•ft•oF (W/m•K)p = Inner perimeter of concrete masonry protection, in. (mm)Tea = Equivalent thickness of concrete masonry protec-

tion, in. (mm)

Table 6—Properties of Concrete Masonry Units

Density, D Thermal conductivity1, kpcf (kg/m3) Btu/hr•ft•oF (W/m•K)

80 (1281) 0.207 (0.358)85 (1362) 0.228 (0.394)90 (1442) 0.252 (0.436)95 (1522) 0.278 (0.481)

100 (1602) 0.308 (0.533)105 (1682) 0.340 (0.588)110 (1762) 0.376 (0.650)115 (1842) 0.416 (0.720)120 (1922) 0.459 (0.749)125 (2002) 0.508 (0.879)130 (2082) 0.561 (0.971)135 (2162) 0.620 (1.073)140 (2243) 0.685 (1.186)145 (2323) 0.758 (1.312)150 (2403) 0.837 (1.449)

1. Thermal conductivity at 70 oF. oC = (oF-32)(5/9)

Effects of Finish MaterialsIn many cases drywall, plaster or stucco finishes are

added to concrete masonry walls. While finishes are nor-mally applied for architectural reasons, they also provideadditional fire resistance value. The Standard (ref. 1) makesprovision for calculating the additional fire resistance pro-vided by these finishes.

It should be noted that when finishes are used to achieve

Figure 3—Control Joints for Fire Resistant Concrete Masonry Assemblies (ref. 1)


Sealant and backerMortar (1/2 in., 13 mmminimum depth)




Sealant and backer

Preformed gasket

Sealant and backer

Bond breaker Sealant and backer

Grout key

Ceramic fiber felt(alumina-silica fibers)

Vertical reinforcementeach side of joint

the required fire resistance rating, the masonry alone mustprovide at least one-half of the total required rating. This isto assure structural integrity during a fire.

Certain finishes deteriorate more rapidly when exposedto fire than when on the non-fire side of the wall. Therefore,two separate tables are required. Table 7 applies to finisheson the non-fire exposed side of the wall and Table 8 appliesto finishes on the fire exposed side.

For finishes on the non-fire exposed side of the wall, the

Figure 4—Details of Concrete Masonry ColumnProtection for Commonly Used Shapes (ref. 1)

tweb

w

d

ps = 2(w + d) + 2(w - tweb) ps = 4d

ps = pd0.25p

0.25p

d

d finish is converted to equivalent thickness of concrete ma-sonry by multiplying the thickness of the finish by the factorgiven in Table 7. This is then added to the base concretemasonry wall equivalent thickness which is used in Table 1to determine the fire resistance rating.

For finishes on the fire exposed side of the wall, a timeis assigned to the finish in Table 8 which is added to the fireresistance rating determined for the base wall and non-fireside finish. The times listed in Table 8 are essentially thelength of time the various finishes will remain intact whenexposed to fire (on the fire side of the wall).

When calculating the fire resistance rating of a wall withfinishes, two calculations are performed. The first is assum-ing fire on one side of the wall and the second is assuming thefire on the other side. The fire rating of the wall assembly isthen the lowest of the two. Note that there may be situationswhere the wall needs to rated with the fire on only one side.

Installation of FinishesFinishes that are assumed to contribute to the total fire

resistance rating of a wall must meet certain minimuminstallation requirements. Plaster and stucco need only beapplied in accordance with the provisions of the buildingcode. Gypsum wallboard and gypsum lath may be attachedto wood or metal furring strips spaced a maximum of 24 in.(610 mm) on center or may be attached directly to the wallwith adhesives. Drywall and furring may be attached in oneof two ways:

Table 8—Time Assigned to Finish Materials onFire Exposed Side of Wall (ref. 1)

Finish description Time, min

Gypsum wallboard 3/8 in. (10 mm) 1/2 in. (13 mm) 5/8 in. (16 mm)

Two layers of 3/8 in. (10 mm) One layer of 3/8 in. (10mm) and one layer of 1/2 in. (16mm) Two layers of 1/2 in. (16 mm)

10152025

3540

Type “X” gypsum wallboard1/2 in. (13 mm)5/8 in. (16 mm)

2540

Direct-applied portland cement-sand plaster See Note 1

Portland cement-sand plaster on metal lath3/4 in. (19 mm)7/8 in. (22 mm)1 in. (25 mm)

202530

Gypsum-sand plaster on 3/8 in. (10 mm)gypsum lath

1/2 in. (13 mm)5/8 in. (16 mm)3/4 in. (22 mm)

354050

Gypsum-sand plaster on metal lath3/4 in. (19 mm)7/8 in. (22 mm)1 in. (25 mm)

506080

1. For purposes of determining the contribution of portland cement- sand plaster to the equivalent thickness of concrete or masonry for use in Table 1, it shall be permitted to use the actual thickness of the plaster, or 5/8 in. (16 mm), whichever is smaller.

Table 7—Multiplying Factor for Finishes on Non-Fire Exposed Side of Wall (ref. 1)

Type of finishapplied to slab

or wall

Type of material used in concretemasonry units

Siliceous orcarbonate aggregateconcrete masonry

unit

Expanded shale,expanded clay,

expanded slag, orpumice less than 20

percent sand

Portland cement-sand plaster1 or

terrazzo1.00 0.75

Gypsum-sandplaster 1.25 1.00

Gypsum-vermic-ulite or perlite

plaster1.75 1.25

Gypsum wall-board 3.00 2.25

1. For portland cement-sand plaster 5/8 in. (16 mm) or less in thickness, and applied directly to concrete masonry on the non-fire- exposed side of the wall, multiplying factor shall be 1.0.



1). Self-tapping drywall screws spaced a maximum of 12 in.(305 mm) and penetrating a minimum of 3/8 in. (10 mm)into resilient steel furring channels running horizontallyand spaced a maximum of 24 in. (610 mm) on center.

2). Lath nails spaced at 12 in. (305 mm) on center maxi-mum, penetrating 3/4 in. (19 mm) into nominal 1 x 2 in.(25 x 51 mm) wood furring strips which are attached tothe masonry with 2 in. (51 mm) concrete nails spaced amaximum of 16 in. (41 mm) on center.Gypsum wallboard must be installed with the long

dimension parallel to the furring members and all horizontaland vertical joints must be supported and finished. The onlyexception is 5/8 in. (16 mm) Type "X" gypsum wallboardwhich may be installed horizontally without being supportedat the horizontal joints.

For drywall attached by the adhesive method, a 3/8 in. (10mm) bead of panel adhesive must be placed around theperimeter of the wallboard and across the diagonals and thensecured with a masonry nail for each 2 ft2 (0.19 m2)of panel.

CONCLUSION

The calculated fire resistance procedure is practical,versatile, and economical. It is based on thousands of tests.It is incorporated by reference into the major model codes ofthe US and allows the designer virtually unlimited flexibilityto incorporate the excellent fire resistive properties of con-crete masonry into the design.

REFERENCES

1. Standard Method for Determining Fire Resistance of Con-crete and Masonry Construction Assemblies, ACI 216.1-97/TMS 0216.1-97. American Concrete Institute and The Ma-sonry Society, 1997.

2. Standard Methods of Sampling and Testing Concrete Ma-sonry Units, ASTM C 140-01. American Society for Testingand Materials, 2001.

3. Standard Specification for Concrete Aggregates, ASTM C33-01. American Society for Testing and Materials, 2001.

4. Standard Specification for Lightweight Aggregates for Con-crete Masonry Units, ASTM C 331-01. American Society forTesting and Materials, 2001.

5. Standard Specification for Lightweight Aggregates forInsulating Concrete, ASTM C 332-99. American Society forTesting and Materials, 1999.

6. Standard Specification for Loadbearing Concrete MasonryUnits, ASTM C 90-01. American Society for Testing andMaterials, 2001.

7. Standard Test Methods for Fire Tests of Building Construc-tion and Materials, ASTM E 119-00a. American Society forTesting and Materials, 2000.

8. Standard Specification for Vermiculite Loose Fill Insulation,ASTM C 516-80(1996)e1. American Society for Testing andMaterials, 1996.

9. Standard Specification for Perlite Loose Fill Insulation, ASTMC 549-81(1995)e1. American Society for Testing and Materials,1995.



CRACK CONTROL INCONCRETE MASONRY WALLS

TEK 10-1AMovement Control (2001)

Keywords: control joints, crack control, joint reinforcement,moisture, reinforced concrete masonry, wall movement

INTRODUCTION

Cracks in buildings and building materials normally resultfrom restrained movement. This movement may originatewithin the material, as with temperature expansion or shrink-age; or may result from movements of adjacent materials, suchas deflection of beams or slabs. In many cases, movement isinevitable and must be accommodated or controlled.

Designing for effective crack control requires an under-standing of the sources of stress which may cause cracking. Itwould be a simple matter to prevent cracking if there were onlyone variable. However, prevention is made more difficult by thefact that cracking often results from a combination of sources.

CAUSES OF CRACKING

There are a variety of potential causes of cracking. Under-

standing the cause of potential cracking allows the designer toincorporate appropriate design procedures to control it. Themost common causes of cracking in concrete masonry areshown in Figure 1 and are discussed below.

Shrinkage/RestraintCracking resulting from shrinkage can occur in concrete

masonry walls because of drying shrinkage, temperature fluc-tuations, and carbonation. These cracks occur when masonrypanels are restrained from moving.

Drying ShrinkageConcrete products are composed of a matrix of ag-

gregate particles coated by cement which bonds themtogether. Once the concrete sets, this cementitious-coated aggregate matrix expands with increasing mois-ture content and contracts (shrinks) with decreasing mois-ture content. Drying shrinkage is therefore a function ofchange in moisture content.

Although mortar, grout, and concrete masonry unitsare all concrete products, unit shrinkage has been shownto be the predominate indicator of the overall wall shrink-

Figure 1 – Proper Design Can Avert Cracking of These Types

Clay brick

Steelbeam

Concretemasonryshrinks

loadShear

a) Shrinkage/restraint b) Differential movement c) Excessive deflection

d) Structural overload e) Differential settlement

expands

age principally due to the fact that it represents the largestportion of the wall. Therefore, the shrinkage properties ofthe unit alone are typically used to establish design criteriafor crack control.

For an individual unit, the amount of drying shrinkage isinfluenced by the wetness of the unit at the time of placementas well as the characteristics and amount of cementitiousmaterials, the type of aggregate, consolidation, and curing.Specifically, drying shrinkage is influenced in the followingways:• walls constructed with "wet" units will experience more

drying shrinkage than drier units ;• increases in cement content increase drying shrinkage;• aggregates which are susceptible to volume change due

to moisture content will result in increased shrinkage;and

• units which have undergone at least one drying cycle willnot undergo as much shrinkage in subsequent dryingcycles (ref. 6).Typical drying shrinkage coefficients range from 0.0002

to 0.00045 in./in. (mm/mm) or 0.24 to 0.54 in. (6.1 to 13.7mm) in 100 ft (30.48 m). The maximum of 0.00065 in./in.(mm/mm) allowed by ASTM C 90, Standard Specificationfor Loadbearing Concrete Masonry Units (ref. 7), is froma 100% saturated condition (immersed in water for 48 hrs.)Typically however, the moisture content of units placed inthe wall is less than 70% accounting for the lower maximumfield value than allowed in the lab.

Standard Test Method for Drying Shrinkage of Con-crete Masonry Units, ASTM C 426 (ref. 8), is the methodfor determining the potential drying shrinkage of concretemasonry units. This is a measure of shrinkage from asaturated moisture content (100%) to that in equilibriumwith a relative humidity of 17% - usually resulting in amoisture content of about 8 to 10% of total absorption.

Temperature ChangesConcrete masonry movement has been shown to be

linearly proportional to temperature change. The coeffi-cient of thermal movement normally used in design is0.0000045 in./in./°F (0.0000081 mm/mm/°C) (ref. 2).Actual values may range from 0.0000025 to 0.0000055 in./in./°F (0.0000045 to 0.0000099 mm/mm/°C) dependingmainly on the type of aggregate used in the unit. The actualchange in temperature is, of course, determined by geo-graphical location and exposure. Other environmental fac-tors may also impact wall temperatures as well. For ex-ample, dark-colored south-facing exterior walls normallyexperience higher temperature fluctuations than lighter col-ored walls or walls with a different orientation.

For typical design purposes, surface wall temperaturesare assumed to range between 0 and 140°F (-18 and 60°C).Expansion and contraction of the wall will occur within thisrange depending on the temperature of the wall at the time ofconstruction. For example, a wall constructed during 70°F(21°C) weather and subjected to a minimum temperature of0°F (-18°C) results in a shortening of about 0.38 in. (9.7mm) in a 100 foot (30.48 m) long wall using the 0.0000045

in./in./°F (0.0000081 mm/mm/°C) coefficient.

CarbonationCarbonation is an irreversible reaction between cemen-

titious materials and carbon dioxide in the atmosphere whichoccurs slowly over a period of several years. Since therecurrently is no standard test method for carbonation shrink-age, it is suggested that a value of 0.00025 in./in. (mm/mm)be used for the carbonation shrinkage coefficient. Thisresults in a shortening of 0.3 in. (7.6 mm) in a 100 foot(30.48 m) long wall.

RestraintAs previously mentioned, the above phenomenon produce

movement in the wall. When external restraint is provided thatresists this movement ,the result is tension within the wall anda corresponding potential for cracking. Typically, concretemasonry walls are restrained along the bottom of the wall withpartial restraint along the top of the wall. The ends of the typicalconcrete masonry wall panel may be partially restrained bypilasters or wall intersections, but this partial restraint usuallydoes not significantly alter the wall's cracking potential. Excep-tions to the typical restraint condition include cantileveredwalls which are restrained along their base, but free (unre-strained) at the top. It is conservative to base general crackcontrol design criteria on a condition of restraint along the topand bottom of the wall.

In addition to external restraint, reinforcement causessome internal restraint within the wall. Reinforcementresponds to temperature changes with corresponding changesin length; however, reinforcement does not undergo volu-metric changes due to moisture changes or carbonation.Consequently, as the wall shrinks, the reinforcement under-goes elastic shortening (strain) which results in compres-sive stress in the steel. Correspondingly, the surroundingmasonry offsets this compression by tension. At the pointwhen the masonry cracks and tries to open, the stress in thereinforcement turns to tension and acts to limit the width ofthe crack by holding it closed.

The net effect is that reinforcement controls crackwidth by causing a greater number (frequency) of cracks tooccur. As the horizontal reinforcement ratio (cross-sec-tional area of horizontal steel vs. vertical cross-sectionalarea of masonry) increases, crack width decreases. Smallersized reinforcement at closer spacings is more effectivethan larger reinforcement at wider spacings, although hori-zontal reinforcement at spacings up to 144 in. (3658 mm) isconsidered effective in controlling crack widths in someareas.

Differential MovementVarious building materials may react differently to

changes in temperature, moisture, or structural loading. Anytime materials with different properties are combined in awall system, a potential exists for cracking due to differen-tial movement. With concrete masonry construction, twomaterials in particular should be considered: clay brick andstructural steel.

Differential movement between clay brick and con-crete masonry must be considered when the two areattached since concrete masonry has an overall tendencyto shrink while clay brick masonry tends to expand. Thesedifferential movements may cause cracking, especially incomposite construction and in walls that incorporatebrick and block in the same wythe.

Composite walls are multi-wythe walls designed toact structurally, as a single unit in resisting applied loads.The wythes are typically bonded together using wall tiesat prescribed intervals to assure adequate load transfer.When the composite wall includes a brick wythe bondedto a concrete masonry wythe, ladder-type joint reinforce-ment, or box ties are used to provide some degree oflateral movement between wythes. In addition, expansionjoints are installed in the clay brick wythe to coincidewith a control joint in the concrete masonry wythe.

When clay brick is used as an accent band in a con-crete masonry wall, or vice-versa, the differential move-ment of the two materials may result in cracking unlessprovisions are made to accommodate the movement. Toprevent cracking a slip plane can be placed between theband and the surrounding wall to accommodate differen-tial shrinkage and expansion. However, the effect of thisslip plane on the structural capacity of the wall should beconsidered. Horizontal reinforcement and frequent con-trol joints will also reduce cracking.

Thermal movement differences also need to be takeninto consideration when using masonry in conjunctionwith structural steel. In addition to differences in ther-mal coefficients, steel shapes typically have a much highersurface area to volume ratio and tend to react to changesin temperature more quickly. This is normally accommo-dated with slotted and flexible connections. ConcreteMasonry Walls for Metal Buildings (ref. 3) providesmore detailed information on this subject.

Excessive DeflectionAs walls and beams deflect under structural loads,

cracking may occur. Additionally, deflection of support-ing members can induce cracks in masonry elements. Toreduce the potential for cracking, the following alterna-tives are available:• adding reinforcing steel into the masonry to cross the

expected cracks and to limit the width of the cracks,• limiting the deflection of members providing vertical

support of unreinforced masonry to acceptable levels(less than or equal to l/600 nor more than 0.3 in. (7.6mm) due to dead load and live load when supportingunreinforced masonry) (ref. 2), and;

• utilizing movement joints to effectively panelize themasonry so that it can articulate with the deflectedshape of the supporting member.

Structural OverloadAll wall systems are subject to potential cracking

from externally applied design loads due to wind, soilpressure or seismic forces. Cracking due to these sources

is controlled by applying appropriate structural designcriteria such as allowable stress design or strength de-sign. These criteria are discussed in detail in AllowableStress Design Tables for Reinforced Concrete MasonryWalls and Strength Design of Tall Concrete MasonryWalls (refs. 1 and 9).

SettlementDifferential settlement occurs when portions of the

supporting foundation subside due to weak or improperlycompacted foundation soils. Foundation settlement typi-cally causes a stair-step crack along the mortar joints inthe settled area as shown in Figure 1(E). Preventingsettlement cracking depends on a realistic evaluation ofsoil bearing capacity, and on proper footing design andconstruction.

Footings should be placed on undisturbed native soil,unless this soil is unsuitable, weak, or soft. Unsuitablesoil should be removed and replaced with compacted soil,gravel, or concrete. Similarly, tree roots, constructiondebris, and ice should be removed prior to placing foot-ings. Adding reinforcement in foundations can also lessenthe effects of differential settlement.

CRACK CONTROL STRATEGIES

In addition to the proper design strategies discussedabove for structural capacity and differential movement,the following recommendations can be applied to limitcracking in concrete masonry walls.

Material PropertiesTraditionally, crack control in concrete masonry has

relied on specifying concrete masonry units with a lowmoisture content, using horizontal reinforcement, andusing control joints to accommodate movement. Prior tothe 2000 edition of ASTM C 90 (ref.7), low moisturecontent was specified by requiring a Type I moisturecontrolled unit. The intent was to provide designers anassurance of units with lower moisture content to mini-mize potential shrinkage cracking. However, there areseveral limitations to relying on moisture content alonesince there are other factors that influence shrinkagewhich are not accounted for by specifying a Type I unit.Additionally, Type I units were not always inventoried byconcrete masonry manufacturers. Most importantly, TypeI units needed to be kept protected until placed in the wall,which was proven to be difficult on some projects.

Because of the above problems associated with theType I specification, ASTM removed the designations ofType I, Moisture-Controlled Units and Type II,Nonmoisture Controlled Units from the standard. Toaccommodate this change, two methods of determiningcontrol joint spacings have been devised irrespective ofunit type: 1). Empirical crack control criteria which isbased on successful, historical performance over manyyears in various geographic conditions and 2). Engi-neered crack control criteria based on a Crack Control


REFERENCES1. Allowable Stress Design Tables for Reinforced Concrete Masonry Walls, TEK 14-19A. National Concrete Masonry

Association, 2000.2. Building Code Requirements for Masonry Structures, ACI 530-99/ASCE 6-99/TMS 402-99. Reported by the Masonry

Standards Joint Committee, 1999.3. Concrete Masonry Walls for Metal Buildings, TR-149. National Concrete Masonry Association, 1996.4. Control Joints for Concrete Masonry Walls, TEK 10-2B. National Concrete Masonry Association, 2001.5. Engineered Crack Control Criteria for Concrete Masonry Walls, TEK 10-3. National Concrete Masonry Association,

2001.6. Measuring Shrinkage of Concrete Block - A Comparison of Test Methods, E.L. Saxer and H.T. Toennies, Pages 988-1004,

1957.7. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90-00. American Society for Testing and

Materials, 1997.8. Standard Test Method for Drying Shrinkage of Concrete Block, ASTM C 426-99. American Society for Testing and

Materials, 1996.9. Strength Design of Tall Concrete Masonry Walls, TEK 14-11A. National Concrete Masonry Association, 1996.

Coefficient (CCC) which includes the combined effectsof movement due to drying shrinkage, carbonation shrink-age, and contraction due to temperature change. The firstis presented in NCMA TEK 10-2B, Control Joints forConcrete Masonry Walls - Empirical Method (ref. 4)and the second in TEK 10-3 Engineered Crack ControlCriteria for Concrete Masonry Walls (ref. 5). For moreinformation on these two methods see TEK 10-2B andTEK 10-3.

Limiting Crack WidthStudies have shown that reinforcement, either in the

form of joint reinforcement or reinforced bond beams,effectively limits crack width in concrete masonry walls.As indicated previously, as the level of reinforcementincreases and as the spacing of the reinforcement de-creases, cracking becomes more uniformly distributedand crack width decreases.

Control JointsControl joints are essentially vertical separations built

into the wall to reduce restraint and permit longitudinalmovement. Because shrinkage cracks in concrete masonryare an aesthetic rather than a structural concern, controljoints are typically only required in walls where shrinkagecracking may detract from the appearance or where waterpenetration may occur. In addition, walls with a relativelylarge amount of horizontal reinforcement may not requirecontrol joints, as the reinforcement alone reduces the widthof shrinkage cracks effectively. For walls that require them,control joints should be located where volume changes inthe masonry due to drying shrinkage, carbonation, tempera-ture changes or other factors are likely to create tension inthe masonry that will exceed its capacity. Specific detailedrecommendations for control joint spacings, steel sizingand spacing, and Crack Control Coefficients are contained inTEK 10-2B (ref. 4) and TEK 10-3 (ref. 5).

Figure 1—Typical Control Joint Locations



CONTROL JOINTS FOR CONCRETE MASONRYWALLS - EMPIRICAL METHOD

TEK 10-2BMovement Control (2001)

Keywords: bond beams, construction details, controljoints, crack control, joint reinforcement, reinforcing bars,reinforced concrete masonry, shrinkage, wall movement

INTRODUCTION

Concrete masonry is a popular construction materialbecause its inherent attributes satisfy the diverse needs ofboth exterior and interior walls. While these attributes arethe primary basis for concrete masonry’s popularity, perfor-mance should not be taken for granted. Like all constructionsystems, design decisions significantly influence field per-formance of the concrete masonry wall system. Properapplication of crack control measures, including controljoints when required, can help ensure satisfactory perfor-mance of the concrete masonry.

Control joints are one method used to relieve horizontal

tensile stresses due to shrinkage of the concrete masonryunits, mortar, and when used, grout. They are essentiallyvertical separations built into the wall at locations wherestress concentrations may occur. These joints reduce re-straint and permit longitudinal movement.

Control joints are typically only required in exposedconcrete masonry walls, where shrinkage cracking maydetract from the appearance of the wall. Shrinkage cracksin concrete masonry are an aesthetic, rather than a struc-tural, concern. In addition, walls with adequate horizontalreinforcement may not require control joints, as thereinforcement effectively reduces the width of shrinkagecracks. Foundation walls traditionally do not include

control joints due to concerns withwaterproofing the joint to withstandhydrostatic pressure. Additionally,since foundation walls are subjectedto relatively constant temperature andmoisture conditions, shrinkage crack-ing in below grade walls tends to beless significant than in above gradewalls.

This TEK focuses on crackingresulting from internal volume changeof the concrete masonry. Potentialcracking resulting from externally ap-plied design loads due to wind, soilpressure, seismic forces, or differ-ential settlement of foundations iscontrolled by limiting the designstress in allowable stress design or byproviding adequate strength whenstrength design is used. These designconsiderations are not covered here.Where external loads are an issue incombination with internal volumechange, the design should considerthe combined effects of these influ-ences on cracking.

ADJACENT

OPENING

HALF JOINT SPACINGMAXIMUM OF ONE

TO

FROM CORNERS BETWEEN MAIN ANDINTERSECTING WALL

PILASTERAT

ADJACENT

OPENINGTO

WALL HEIGHTAT CHANGES IN

Table 1—Recommended Control Joint Spacing forAbove Grade Exposed Concrete Masonry Wallsa

Distance between joints should not exceed the lesser of:Length to height ratio or ft (m)

1½ 25 (7.62)

a Notes:1. Table values are based on the use of horizontal reinforcement

having an equivalent area of not less than 0.025 in.2/ft (52.9mm2/m) of height to keep unplanned cracks closed (see Table 2).

2. Criteria applies to all concrete masonry units.3. This criteria is based on experience over a wide geographical

area. Control joint spacing should be adjusted up or down wherelocal experience justifies but no farther than 25 ft (7.62 m).

CONTROL JOINT PLACEMENT

When required, control joints should be located wherevolume changes in the masonry due to drying shrinkage,carbonation, or temperature changes are likely to createtension in the masonry that will exceed its capacity. Inpractice, this can be difficult to determine, but several meth-ods are presented in the following sections to provide guid-ance in locating control joints.

In addition, care should be taken to provide joints atlocations of stress concentrations such as (see Figure 1):1. at changes in wall height,2. at changes in wall thickness, such as at pipe and duct

chases and pilasters,3. at (above) movement joints in foundations and floors,4. at (below) movement joints in roofs and floors that bear

on a wall,5. near one or both sides of door and window openings,

(Generally, a control joint is placed at one side of anopening less than 6 ft (1.83 m) wide and at both jambs of

Table 2—Maximum Spacing of HorizontalReinforcement to Achieve 0.025 in.2/ft (52.9 mm2/m)

Criteria

Maximum spacing, Reinforcement size in. (mm)2a x W1.7 (9gage)(MW 11) 16 (406)2a x W2.1 (8gage)(MW 13) 16 (406)2a x W2.8 (3/16 in.)(MW 18) 24 (610)4b x W1.7 (9gage)(MW 11) 32 (813)4b x W2.1 (8gage)(MW 13) 40 (1016)4b x W2.8 (3/16 in.)(MW 18) 48 (1219)No. 3 (M10) 48 (1219)No. 4 (M13) 96 (2348)No. 5 (M16) or larger 144 (3658)

Notes:a. Indicates 2 wires per course, one in each faceshell.b. Indicates 4 wires per course, two in each faceshell.

openings over 6 ft (1.83 m) wide. Control joints can beaway from the opening if adequate tensile reinforce-ment is placed above, below, and beside wall openings.)

6. adjacent to corners of walls or intersections within adistance equal to half the control joint spacing.

EMPIRICAL CRACK CONTROL CRITERIA

For walls without openings or other points of stressconcentration, control joints are used to effectively di-vide a wall into a series of isolated panels. Table 1 listsrecommended maximum spacing of these control jointsbased on empirical criteria. This criteria has beendeveloped based on successful, historical performanceover many years in various geographical conditions. Italso assumes that units used in the construction complywith the minimum requirements of ASTM C 90-00 Stan-dard Specification for Loadbearing Concrete MasonryUnits (ref. 1) and that a minimum amount of horizontalreinforcement is provided as indicated in Footnote 1 ofTable 1. It is intended to provide the most straightforwardguidelines for those cases where detailed properties ofthe concrete masonry are not known at the time of design.As indicated in Footnote 3 of Table 1, local experiencemay justify an adjustment to the control joint spacingspresented in the table.

To illustrate these criteria, consider a 20 ft (6.10 m) tallwarehouse with walls 100 ft (30.48 m) long. Table 1indicates control joints spaced every 25 ft (7.62 m). Inthis example, the maximum spacing of 25 ft (7.62 m)governs over the maximum length to height ratio of 1½times 20 ft (6.10 m) or 30 ft (9.14 m). For wallscontaining masonry parapets, consider the parapet as partof the masonry wall below if it is connected by masonrymaterials such as a bond beam unit when determining thelength to height ratio.

The control joint spacings of Table 1 have been devel-oped based on the use of horizontal reinforcement to keepunplanned cracks closed as indicated in Footnote 3. Theminimum area of reinforcement given, 0.025 in.2/ft (52.9mm2/m) of height, translates to horizontal joint reinforce-ment spaced as indicated in Table 2.

CONSTRUCTION

Common control joints are illustrated in Figure 2. Thejoints permit free longitudinal movement, but may need totransfer lateral or out-of-plane shear loads. These loads canbe transferred by providing a shear key, as shown in Figure 2a,2d and 2f. Figure 2e shows smooth dowel bars placed acrossthe control joint to transfer shear. The dowels are typicallygreased or placed in a plastic sleeve to reduce bond and allowthe wall to move longitudinally. Control joints also must beweather-tight when located in exterior walls.

Nonstructural reinforcement, such as horizontal jointreinforcement which is mostly used for crack control only,should not be continuous through a control joint, since this

Figure 2—Typical Control Joint Details

HOUR FIRE RATING

USED TO ACCOMMODATE REINFORCEMENT IS

SMOOTH DOWELS (GREASEDOR SLEAVED TO MINIMIZEBOND TO GROUT)

BLANKET FOR 4

BACKER ROD

PREFORMED

BUILDING

ROD AND SEALANTSEAL WITH BACKER RAKE JOINT AND

PAPER

AT CONTROL

STOP JOINT

GROUTFILL

REINFORCEMENT

JOINT

TERMINATED 2 IN. (51 mm)

DIAPHRAGM CHORD TENSION)

(EXCEPT WHEN

JOINT SEALER

BACKER ROD

JOINT FILLER

IF REQUIREDVERTICAL BARS

CERAMIC FIBER

HORIZONTAL BARS TERMINATED

REINFORCEMENT IS USED TO JOINTS (EXCEPT WHEN 2 IN. (51 mm) FROM CONTROL

BACKER RODAND JOINT SEALANT

IF REQUIREDVERTICAL BARS

JOINT SEALER

AND SEALANT

RAKE JOINT AND SEALWITH BACKER ROD

BACKER ROD AND

VERTICAL BARSIF REQUIRED

JOINT SEALERVERTICAL BARSIF REQUIRED

ACCOMMODATE DIAPHRAGM CHORD TENSION)

HORIZONTAL BARS

FROM CONTROL JOINTS

Figure 2c—Discontinuous Horizontal Reinforcement Figure 2d—Formed Paper Joint

Figure 2f—Special Shaped UnitsFigure 2e—Doweled Joint (for Shear Transfer)

Figure 2a—Preformed Gasket Figure 2b—4 Hour Fire Rated Control Joint


will restrict horizontal movement. However, structural rein-forcement, such as bond beam reinforcement at floor androof diaphragms that resists diaphragm cord tension, must becontinuous through the control joint.

Where concrete masonry is used as a backup for othermaterials, consider the following:1. control joints should extend through the facing when

wythes are rigidly bonded,2. control joints need not extend through the facing when

bond is flexible (i.e. metal ties). However, depending onthe type of facing, considerations should be given to crack

control in the facing material as well.For example, control joints should extend through plas-

ter applied directly to masonry units. Plaster applied on lathwhich is furred out from masonry may not, however, requirevertical separation at control joints.

REFERENCES

1. Standard Specifications for Loadbearing ConcreteMasonry Units, ASTM C 90-01. American Society forTesting and Materials, 2001.

12-1A: ANCHORS AND TIES FOR MASONRY

INTRODUCTION

Anchors and ties are types of connectors which attach masonry to a structural support system, or which connect two or more wythes of masonry together. The design of connectors is covered by national standards (refs. 2, 4) and by model building codes (refs. 1, 5, 6, 7). The provisions of these codes and standards require that connectors be designed to resist applied loads and that the type, size, and location of connectors be shown or indicated on project drawings. The design criteria, illustrations, and tables provided in this TEK are presented as a guide to assist the designer in determining anchor and tie capacity in accordance with the applicable standards and building code requirements. DESIGN CRITERIA

Regardless of whether connectors are being used to connect wythes of masonry, intersecting walls, or masonry walls to the structural frame, they play a very important role in providing structural integrity and good serviceability. As a result, when selecting connectors for a project, designers should consider a number of design criteria. Connectors should: 1. Transmit out-of-plane loads from one wythe of masonry to another or from masonry to its lateral support with a minimum amount of deformation. It is important to reduce the potential for cracking in masonry due to deflection. There is no specific criteria on the stiffness of connectors, but some authorities suggest that a stiffness of 2000 lb/in. (350 kN/m) is a reasonable target. 2. Allow differential in-plane movement between two masonry wythes connected with ties. This design criterion is especially significant as more and more insulation is used between the outer and inner wythes of cavity walls or where wythes of dissimilar materials are anchored together. On the surface, it appears that this criterion is in conflict with Item 1, but simply means that connectors must be stiff in one direction (out-of-plane) and flexible in the other (in-plane). Where control joints are necessary, they are typically designed to accommodate a movement of 3/16 in. (4.8 mm). Therefore, a designer can base the needed in-plane flexibility of the connector on this quantity. Some connectors allow much more movement than unreinforced masonry can tolerate, so designers should not assume that walls can actually move as much as the connector will allow without cracking the masonry. Additionally, cavity widths are limited to less than 4.5 in. (114 mm) so as not to compromise both the in-plane and out-of-plane stiffness of the wall ties (ref. 2). 3. Provide adequate corrosion protection. The protection of anchors and ties from the effects of environmental exposure is an extremely important consideration in any design. Where stainless steel anchors and ties are specified, Specification for Masonry Structures (ref. 4) requires that AISI Type 304 stainless steel be provided that complies with the following:

� Joint reinforcement – ASTM A 580 � Sheet metal anchors and ties – ASTM A 167 � Wire ties and anchors – ASTM A 580

Where carbon steel ties and anchors are specified, protection from corrosion shall be provided by either galvanizing or epoxy coating in conformance with the following (ref. 4):

A. Galvanized coatings:

� Joint reinforcement, interior walls – ASTM A 641 (0.1 oz zinc/ft2) (0.031 kg zinc/m2)

� Joint reinforcement, wire ties or anchors, exterior walls – ASTM A 153 (1.5 oz zinc/ft2) (0.46 kg zinc/m2) � Sheet metal ties or anchors, interior walls – ASTM A 653 Class G60 � Sheet metal ties or anchors, exterior walls – ASTM A 153 Class B

B. Epoxy coatings:

Provided by: Grace Construction Products

Keywords: anchorage, cavity walls, column anchorage, connectors, corrosion protection, joint reinforcement, veneer, wall anchorage, wall ties

Page 1 of 612-1A: ANCHORS AND TIES FOR MASONRY

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� Joint reinforcement – ASTM A 884 Class B Type 2 (18 mils) (457 µm) � Wire ties and anchors – ASTM A 899 Class C Type 2 (20 mils) (508 µm) � Sheet metal ties and anchors – Per manufacturer’s specification (or 20 mils) (508 µm)

4. Accommodate construction by being simple in design and easy to install. Connectors should not be so large and cumbersome as to leave insufficient room for mortar in the joints. Connectors that take up considerable space in a bed joint will result in a greater tendency to allow water migration into the wall. In the same way, connectors should readily accommodate installation of rigid board insulation in wall cavities when necessary. TYPES OF CONNECTORS

There are three types of connectors: wall ties, anchors, and fasteners. Wall ties connect one masonry wythe to an adjacent wythe. Anchors connect masonry to a structural support or frame. Fasteners connect an appliance to masonry. This TEK covers metal wall ties and anchors. Fasteners should be used strictly in accordance with the manufacturer's recommendations. Wall Ties Building Code Requirements for Masonry Structures (ref. 2) has a number of prescriptive requirements for wire wall ties and strap-type ties for intersecting walls. Wire wall ties can be either one piece unit ties, adjustable two piece ties, joint reinforcements or prefabricated assemblies made up of joint reinforcement and adjustable ties. Figure 1 shows typical wall ties. Wall ties do not have to be engineered unless the nominal width of a wall cavity is greater than 4.5 in. (114 mm). The prescribed size and spacing is presumed to provide connections that will be adequate for the loading conditions covered by the code.

Truss-type joint reinforcement is not recommended for tying the wythes of an insulated cavity wall together. In addition, truss type joint reinforcement should not be used when the cavity wall is constructed using concrete masonry backup and a clay brick outer wythe. The truss shape is relatively more stiff in the plane of a wall with respect to ladder type joint reinforcement, and hence restricts more differential movement. Ladder type joint reinforcement is less rigid, and is recommended when either of these conditions occur or when vertical reinforcement is used.



Table 1 summarizes code prescriptive requirements for unit wall ties and joint reinforcement. Figure 2 also shows additional requirements for adjustable wall ties.

Anchors Building Code Requirements for Masonry Structures (ref. 2) contains no prescriptive requirements for wall anchors, but does imply that they be designed with a structural system to resist wind and earthquake loads and to accommodate the effects of deformation. Typical anchors are shown in Figure 3. The shapes and sizes of these typical anchors have evolved over many years and satisfy the “constructability” criterion. All of the anchors shown have been tested with the resulting capacities as shown in Table 2.



Additional tests are needed for adjustable anchors of different configurations and for one piece anchors. Proprietary anchors are also available. Manufacturers of proprietary anchors should furnish test data to document comparability with industry tested anchors. Anchors are usually designed based on their contributory area. This is the traditional approach, but some computer models suggest that this approach does not always reflect the actual behavior of the anchorage system. However, there is currently no accepted computer program to address this point, so most designers still use the contributory area approach with a factor of safety of 3. The use of additional anchors near the edges of wall panels is also recommended and required around large openings.



CONSTRUCTION

When typical ties and anchors are properly embedded in mortar or grout, mortar pullout or pushout will not usually be the controlling mode of failure. The standard (ref. 4) requires that connectors must be embedded at least 11/2 in. (38 mm) into a mortar bed of solid units. The required embedment of unit ties in hollow masonry is such that the tie must extend completely across the hollow units (Figure 4). Proper embedment can be easily attained with the use of prefabricated assemblies of joint reinforcement and unit ties. Because of the magnitude of loads on anchors, it is recommended that they be embedded in filled cores of hollow units. To save mortar, screens can be placed under the anchor and 1 to 2 in. (25 to 51 mm) of mortar can be built up into the core of the block above the anchor (Figure 5).

REFERENCES

1. BOCA National Building Code. Country Club Hills, IL. Building Officials and Code Administrators International, Inc. (BOCA), 1999. 2. Building Code Requirements for Masonry Structures, ACI 530-99/ASCE 5-99/TMS 402-99. Reported by the Masonry Standards Joint Committee, 1999. 3. Porter, Max L., Lehr, Bradley R., Barnes, Bruce A., Attachments for Masonry Structures, Engineering Research Institute, Iowa State University, February 1992. 4. Specification for Masonry Structures, ACI 530.1-99/ASCE 6-99/TMS 602-99. Reported by the Masonry Standards Joint Committee, 1999. 5. Standard Building Code. Birmingham, AL. Southern Building Code Congress International, Inc. (SBCCI), 1999. 6. Uniform Building Code. Whittier, CA. International Conference of Building Officials (ICBO), 1999. 7. 2000 International Building Code, Falls Church, VA. International Code Council, 2000.



of 612-1A: ANCHORS AND TIES FOR MASONRY


12-2A: THE STRUCTURAL ROLE OF JOINT REINFORCEMENT IN CONCRETE MASONRY

Introduction

Joint reinforcement for masonry is a factory-fabricated welded wire assembly consisting of two or more longitudinal wires connected with cross wires forming a truss or ladder configuration. The primary function for which it was initially conceived is the control of wall cracking associated with thermal or moisture shrinkage or expansion. Its exemplary performance in this function is well known, and adequately discussed elsewhere (ref. 2). Less well known are its secondary functions of: (1) metal tie system for bonding adjacent masonry wythes in composite, faced, cavity, and veneer wall constructions, and (2) structural steel reinforcement increasing masonry’s resistance to flexural, shear, and tensile stresses.

Bending Strength

Joint reinforcement increases a wall’s resistance to horizontal bending. The effectiveness of joint reinforcement in the horizontal span depends on several factors, discussed below.

Bond Pattern

The measured relative flexural strength of 8 in. (203 mm) thick concrete masonry walls spanning 8 ft (2.4 m) horizontally is shown in Figure 1 for two common bonding patterns, both with and without joint reinforcement (ref. 3). Without joint reinforcement, the tested strength of a stacked bond wall is approximately 40 percent that of a wall laid in running bond. This difference in strength of unreinforced walls is reflected in code allowable flexural tension stresses which are twice as large for stresses parallel to the bed joint as they are for stresses perpendicular to the bed joint (ref. 1).

When joint reinforcement is placed at 16 in. (406 mm) intervals, the strength of the two different bonding patterns is increased to the same level (Figure 1). For the running bond wall, joint reinforcement at 16 in. (406 mm) increased wall strength 20 percent. For the stacked bond wall, the improvement was three-fold (3 x 40 = 120). With joint reinforcement spaced at 8 in. (203 mm) vertically, a four-fold improvement was observed for the stacked bond wall, and 60 percent improvement for running bond.

Mortar Strength & Bond

The comparisons shown in Figure 1 are from tests on walls built with mortar having sufficient strength and bond to fully develop the tensile strength of the deformed longitudinal wire reinforcement. In this regard it is noteworthy that slippage of the deformed side wires is resisted not only by surface bond but also by the mechanical anchorage afforded by the embedded portions of the weld-connected cross wires. When masonry unit faceshells are mortared, some excess mortar is squeezed out onto the cross web. It follows, then, that anchorage of the joint reinforcement is increased when the cross wires align with the block webs.


Keywords: cavity wall, connectors, flexural strength, joint reinforcement, multiwythe wall, wall ties

Page 1 of 612-2A: The Structural Role of Joint Reinforcement in Concrete Masonry


It is logical that mortar strength and bond should be influencing factors, especially with respect to the larger wire sizes. Test data supporting this view are summarized graphically in Figure 2. In these tests the compressive strengths of the mortars were 3540 psi (24 MPa) for Type S mortar and 1100 psi (8 MPa) for Type N mortar. Walls built with the stronger mortar exhibited a steady increase in flexural strength as the amount of joint reinforcement was increased. In contrast, walls built with the weaker mortar did not benefit by increasing the reinforcement above the minimum amount.

Data pertaining more specifically to the bond between deformed wire and mortar are given in Table 1. Taken from pullout tests, the data indicate that 4 in. (102 mm) of embedment is insufficient in many cases to fully develop the strength of the wire. When splicing joint reinforcement, a 6 in. (152 mm) lap is recommended, since it provides sufficient embedment to develop full tensile strength of the wire. In addition, the data suggest that when 3/16 in. (5 mm) longitudinal wires are employed, the accompanying mortar should be either Type S or Type M.



Design Strength

Table 2 shows the allowable moment capacity of single-wythe hollow concrete masonry walls spanning horizontally, with and without joint reinforcement. As noted in footnote C, the calculated moment capacity is lower, in a few cases, for walls with joint reinforcement than for walls without joint reinforcement. This discrepancy is due to the design assumption in reinforced concrete masonry that the tensile strength of the masonry is ignored and all tensile force is carried by the steel reinforcement. For these cases, the wall should be designed as an unreinforced wall or the amount of joint reinforcement should be increased so that the reinforced capacity exceeds the unreinforced capacity.

Multi-Wythe Walls

The welded cross wires of joint reinforcement are considered acceptable ties for bonding the wythes of composite walls, cavity walls



and veneer to backups. In composite walls with a solidly-filled collar joint, the cross wires hold the units together so that the combination of units can be treated as a single solid structural element. In cavity walls and veneer, the metal cross wires transfer direct tensile and compressive forces from one masonry wythe to the other, but are not considered effective in resisting shear. However, tests have indicated that the cross wires in joint reinforcement do, in fact, provide some transfer of longitudinal shear across the wall cavity (ref. 4).

There are a number of advantages to using joint reinforcement for bonding multiwythe walls:

1. When joint reinforcement is compared to other types of connectors (Z-ties, rectangular ties, and masonry headers), walls of the various types will have about the same initial flexural strength, but the wall with joint reinforcement will maintain greater structural integrity after cracking. Walls tied with joint reinforcement resist 75 to 90 percent of the maximum test load after initial cracking.

2. Walls subjected to racking loads sufficient to cause diagonal cracking are protected from failure by the longitudinal wires of the joint reinforcement. Horizontal steel is roughly three times as efficient as vertical steel in carrying racking shear loads.

3. Walls tied with joint reinforcement resist cracking due to thermal or moisture shrinkage and expansion.

Cavity Width

To gage the impact of increasing cavity width, compressive buckling strength tests were conducted on two joint reinforcement-wall tie configurations spanning three different cavity widths. The test specimens are shown in Figure 3, while Table 3 lists pertinent details of the specimens and results of the test. As noted, all tests were duplicated with both crimped and straight wire spanning the cavity.



For both joint reinforcement configurations (truss and rectangular), crimps created to form a cavity drip in the cross wires significantly reduced load carrying capacity, the reduction varying from about one-half when the cavity width was 23/4 in. (70 mm) to no reduction with the 7 in. (178 mm) cavity. Based on this, Building Code Requirements for Masonry Structures (ref. 1) requires a 50% reduction in the spacing when cavity drips are used.

Recommendations

Recommendations for the use of different types of joint reinforcement are listed in Table 4.



References

1. Building Code Requirements for Masonry Structures, ACI 530-95/ASCE 5-95/TMS 402-95. Reported by the Masonry Standards Joint Committee, 1995. 2. Control of Wall Movement with Concrete Masonry, NCMA TEK 10-2. National Concrete Masonry Association, 1972. 3. Load Tests of Patterned Concrete Masonry Walls. Skokie, IL: Portland Cement Association. 4. Investigation of Masonry Wall Ties, ARF B-870-2. Armour Research Foundation of Illinois Institute of Technology, 1962.



12-3: ANCHOR BOLTS FOR CONCRETE MASONRY

Introduction

The function of anchor bolts is to transfer loads to the masonry from attachments such as ledgers, sill plates, weld plates, etc. As illustrated in Figure 1, both shear and tension are transferred through anchor bolts in resisting design forces such as uplift due to wind or vertical loads on ledgers due to gravity. The magnitude of these loads will vary significantly. The purpose of this TEK is to assist the designer in determining the proper size, embedment length and spacing of bolts to resist design loads.

Anchor bolts can generally be divided into two categories: embedded anchor bolts which are placed in the grout during construction of the masonry; and drilled-in anchors which are placed after construction of the masonry.

Drilled-in anchors achieve shear and tension (pull out) resistance by means of expansion against the masonry or sleeves, or by bonding with epoxy or other adhesives. The design of drilled-in anchors should be in accordance with manufacturer ’literature and is outside the scope of this TEK.

Types of Embedded Anchor Bolts

Conventional bolts are available in standard sizes (diameters and lengths) or can be fabricated to meet specific project requirements. The types of conventional anchors most commonly specified are illustrated in Figure 2. These consist of headed, bent bar, and plate anchor bolts.


Keywords: allowable stress, anchorage, connectors, wall anchorage, wall ties

Page 1 of 712-3: Anchor Bolts for Concrete Masonry

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Headed anchor bolts are usually of either the square or hex-headed variety and are popular due to their wide availability and relatively low cost. Washers are placed against the bolt head for the purpose of enlarging the bearing area and thereby increasing pullout resistance.

Bent bar anchor bolts are currently fabricated in a variety of shapes, since no standard exists governing the geometric properties, with the “L” and “J”shapes being the most common. The design provisions in this TEK are based on a bolt with a 90 degree bend and an extension of 1 1/2 bolt diameters. The inside diameter of bend should be at least three bolt diameters.

Plate anchor bolts are fabricated by welding a square or circular steel plate at right angles to the axis of a steel bar. The dimensions of the steel plate (length, width, or diameter) should be at least one inch plus the bolt diameter and the thickness should be at least 0.4 times the bolt diameter.

Applications/Uses

In most new masonry construction, anchor bolts are commonly embedded at:

� tops of walls xattach sill plates and weld plates for the purpose of supporting wood and steel joists, trusses, and beams � tops of walls xattach sill plates and weld plates for the purpose of supporting wood and steel joists, trusses, and beams � surfaces of walls xattach wood or steel ledger beams used to support wood and steel joists and trusses

Design Requirements

The design provisions for anchor bolts presented here are excerpts from Building Code Requirements for Masonry Structures (ref. 2) which is referenced by the BOCA National Building Code and Standard Building Code (refs. 1, 3). These provisions are also written into the Uniform Building Code (ref. 5).

Definition:

Connector mechanical device for securing two or more pieces, parts, or members together, including anchors, wall ties and fasteners.

Notations:

Ab = cross-sectional area of an anchor bolt, in.2 (mm2)

Ap = projected area on the masonry surface of a right circular cone for anchor bolt allowable shear and tension calculations, in.2

(mm2) ba = total applied design axial force on an anchor bolt, lb (N) Ba = allowable axial force on an anchor bolt, lb (N) bv = total applied design shear force on an anchor bolt, lb (N) Bv = allowable shear force on an anchor bolt, lb (N)



db = nominal diameter of anchor bolt, in. (mm) f’m = specified compressive strength of masonry, psi (MPa) fy = specified yield stress of steel for reinforcement and anchors, psi (MPa) lb = effective embedment length of plate, headed or bent anchor bolts, in. (mm) lbe = anchor bolt edge distance measured from the surface of an anchor bolt to the nearest free edge of masonry, in. (mm)

5.14 Anchor Bolts Solidly Grouted in Masonry 5.14.1 Test design requirements Except as provided in Section 5.14.2, anchors shall be designed based on the following provisions. 5.14.1.1 Anchors shall be tested in accordance with ASTM E 488 under stresses and conditions representing intended use except that at least five tests shall be performed. 5.14.1.1 Anchors shall be tested in accordance with ASTM E 488 under stresses and conditions representing intended use except that at least five tests shall be performed. 5.14.2 Plate, headed and bent bar anchor bolts The allowable loads for plate anchors, headed anchor bolts, and bent bar anchor bolts (J or L type) embedded in masonry shall be designed in accordance with the provisions of Sections 5.14.2.1 through 5.14.2.4. 5.14.2.1 The minimum effective embedment length shall be 4 bolt diameters, but not less than 2 in. (51 mm). 5.14.2.2 The allowable load in tension shall be the lesser of that given by Eq. (5-1) or Eq. (5-2).

Ap = π lbe2 (5-1)

Ba = 0.2Abfy (5-2)

(a) The area Ap shall be the lesser of Equation 5-3 or Equation 5-4. Where the projected areas of adjacent anchor bolts overlap, p of each bolt shall be reduced by one half of the overlapping area. That portion of the projected area falling in an open cell or core shall be deducted from the value of p calculated using Equations 5-3 or 5-4.

Ap = π lb2 (5-3)

Ap = π lbe2 (5-4)

(b) The effective embedment length of plate or headed bolts, lb, shall be the length of embedment measured perpendicular from the surface of the masonry to the bearing surface of the plate or head of the anchor bolt.

(c) The effective embedment length of bent anchors, lbe, shall be the length of embedment measured perpendicular from the surface of the masonry to the bearing surface of the bent end minus one anchor bolt diameter.

5.14.2.3 The allowable load in shear, where lbe equals or exceeds 12 bolt diameters, shall be the lesser of that given by Eq. (5-5) or Eq. (5-6).

Where lbe is less than 12 bolt diameters, the value of Bv in Equation (5-5) shall be reduced by linear interpolation to zero at an lbe distance of 1 in. (25 mm).

5.14.2.4 Combined shear and tension: Anchors in Section 5.14.2 subjected to combined shear and tension shall be designed to satisfy Eq. (5-7).



The minimum effective embedment length is illustrated in Figure 4. When anchor bolts penetrate the face shells of a masonry unit, the opening in the face shell shall be wide enough to provide at least 1 in. (25 mm) of cover around the perimeter of the bolt.

Minimum edge distance requirements are illustrated in Figure 5.



Allowable Tension and Shear



The following tables include allowable tension values for bent bar anchor bolts embedded in concrete masonry with f’ m equal to 1500 psi and 2500 psi.

Construction

In order to keep the anchor bolts properly aligned during placement of the grout, templates are required to hold the bolts within the necessary tolerances. Templates can be either of wood or steel, depending upon the degree of accuracy required. Tolerances of 1/4 in. (6.4 mm) can be maintained using wood templates, while closer tolerances usually require the use of steel.

Locating and drilling the holes in the template after placement is recommended. To be sure that the bolts are not disturbed during the grouting operation, nuts and washers on both sides of the templates should be used to hold them securely in position.

References

1. BOCA National Building Code. Country Club Hills, IL: Building Officials and Code Administrators International, Inc. (BOCA), 1993. 2. Building Code Requirements for Masonry Structures, ACI 530-95/ASCE 5-95/TMS 402-95. Reported by the Masonry Standards Joint Committee, 1995. 3. Standard Building Code. Birmingham, AL: Southern Building Code Congress International, Inc. (SBCCI), 1994. 4. Standard Test Methods for Strength of Anchors in Concrete and Masonry Elements, ASTM E 488-90. American Society for Testing and Materials, 1990. 5. Uniform Building Code. Whittier, CA: International Conference of Building Officials (ICBO), 1994.

Table 1 Allowable Tension, lb f’m = 1500 psi

Bolt diameter, db, in.

lb* 1/4 3/8 1/2 5/8 3/4 7/8 1 1 1/8

4db

6db

8db

10db

60 130 240 360

130 310 550 790

240 540 970

1440

380 850

1520 2230

540 1230 2190 3160

740 1670 2980 4320

970 2180 3890 5680

1240 2770 4920 7130

* Use lesser of Ib or Ibe

Table 2 Allowable Tension, lb f’m = 2500 psi


lb* 1/4 3/8 1/2 5/8 3/4 7/8 1 1 1/8

4db

6db

8db

10db

80 180 310 360

180 400 710 790

310 710

1260 1440

490 1105 1960 2230

710 1590 2820 3120

960 2160 3850 4320

1260 2820 5025 5690

1600 3570 6350 7130

* Use lesser of Ib or Ibe

Table 3 Allowable Shear, lb1, 2


fm 1/4 3/8 1/2 5/8 3/4 7/8 1 1 1/8

1500 2000 2500 3000 3500

210 210 210 210 210

480 480 480 480 480

850 850 850 850 850

1330 1330 1330 1330 1330

1780 1900 1900 1900 1900

1920 2060 2180 2280 2370

2050 2200 2330 2440 2540

2170 2340 2470 2590 2680

1 lbe > 12db

2 fy= 36,000 psi



of 712-3: Anchor Bolts for Concrete Masonry


12-4C: STEEL REINFORCEMENT FOR CONCRETE MASONRY

INTRODUCTION

Reinforcement incorporated into concrete masonry walls increases strength and ductility, provides increased resistance to applied loads, and in the case of horizontal reinforcement, provides increased resistance to shrinkage cracking. This TEK covers non-prestressed reinforcement for concrete masonry construction. Prestressing steel is discussed in Post-Tensioned Concrete Masonry Wall Construction, TEK 3-14 (ref. 12).

MATERIALS

Reinforcement types used in masonry principally are reinforcing bars and cold-drawn wire products. Wall anchors and ties are usually formed of wire, metal sheets or strips. Table 1 lists applicable ASTM Standards governing steel reinforcement, as well as nominal yield strengths for each steel type.

Reinforcing Bars In the United States, reinforcing bars are manufactured in eleven standard bar sizes designated No. 3 through 11 (M #10 - 36), No. 14 (M #43), and No. 18 (M #57). The bar size number designates the nominal diameter in eighths of an inch (or the diameter in millimeters for metric equivalents) as shown in Table 2. The actual specified diameter (which is used for design purposes) may vary slightly from the nominal diameter. Bar sizes larger than No. 11 (M #36) (No. 9 (M #29) for masonry designed by strength design provisions) are not permitted in masonry work (ref. 1).

As a means of field identification, reinforcing bar manufacturers mark the bar size, producing mill identification, type of steel and grade of steel on the reinforcing bars (see Figure 1).

Each applicable ASTM standard includes minimum requirements for various physical properties including yield strength and stiffness. While not all reinforcing bars have a well-defined yield point, the modulus of elasticity, Es , is roughly the same for all reinforcing steels and for design purposes is taken as 29,000,000 psi (200 GPa).

When designing by allowable stress design methods, the allowable tensile stress is limited to 20,000 psi (138 MPa) for Grade 40 or


Keywords: allowable stress, ASTM specifications, corrosion protection, development, embedment, joint reinforcement, reinforcing bars, reinforcing steel, splice, standard hooks, strength design, wall ties, wire

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50 reinforcing bars and 24,000 psi (165 MPa) for Grade 60 reinforcing bars. For reinforcing bars enclosed in ties, such as those in columns, the allowable compressive stress is limited to 40% of the specified yield strength, with a maximum of 24,000 psi (165 MPa). For strength design, the nominal yield strength of the reinforcement is used to size and distribute the steel.

Cold-Drawn Wire ASTM A 951 (ref. 6) is the standard for joint reinforcement used in masonry. Cold-drawn wire for joint reinforcement, ties or anchors varies from W1.1 to W4.9 (MW7 to MW32) with the most popular size being W1.7 (MW11). Table 3 shows standard wire sizes and properties. Because current codes (ref. 1) limit the size of joint reinforcement to one half the joint thickness, the practical limit for wire diameter is 3/16 in. (W2.8, 4.8 mm, MW18) for a 3/8 in. (9.5 mm) bed joint. Wire for masonry is plain with the exception that side wires for joint reinforcement are deformed by means of knurling wheels.

Stress-strain characteristics of reinforcing wire have been determined by extensive testing programs. Not only is the yield strength of cold-drawn wire close to its ultimate strength, but the location of the yield point is not clearly indicated on the stress-strain curve. ASTM A 82 (ref. 8) defines yield as the stress determined at a strain of 0.005 in./in. (mm/mm).

CORROSION PROTECTION

Grout, mortar, and masonry units usually provide adequate protection for embedded reinforcement provided that minimum cover and clearance requirements are met. Specification for Masonry Structures (ref. 3) allows reinforcement with a moderate amount of rust to be used without cleaning or brushing. Reinforcing bars may be used as long as the rust is not so severe that a wire-brushed sample fails to comply with the minimum dimensions and weight required by the applicable ASTM specification.

Joint Reinforcement Carbon steel can be protected from corrosion by coating the steel with zinc (galvanizing). The zinc protects steel by acting as a barrier between the steel and oxygen and water. During the corrosion process, the zinc is also sacrificed before the steel is attacked. The protective value of the zinc coating increases with increased coating thickness; therefore the required amount of galvanizing increases



with the severity of exposure, as listed below.

Mill galvanized: • for joint reinforcement in interior walls exposed to a mean relative humidity less than or equal to 75% ASTM A 641 (ref. 10) 0.1 oz/ft2 (0.031 kg/m2)

Hot-dip galvanized: • joint reinforcement in exterior walls or in interior walls exposed to a mean relative humidity exceeding 75% ASTM A 153 (ref. 9) 1.5 oz/ft2 (0.46 kg/m2)

Alternatively, corrosion protection can be provided by stainless steel joint reinforcement, AISI Type 304 or Type 316 conforming to ASTM A 580 (ref. 7) or epoxy coatings in accordance with ASTM A 884 (ref. 15) Class B Type 2, 18 mils (457 mm).

In addition, joint reinforcement must be placed so that longitudinal wires are embedded in mortar with a minimum cover of 1/2 in. (13

mm) when not exposed to weather or earth, and 5/8 in. (16 mm) when exposed to weather or earth.

Reinforcing Bars Building Code Requirements for Masonry Structures requires a minimum amount of masonry cover over reinforcing bars to protect against steel corrosion. This masonry cover is measured from the exterior masonry surface to the outermost surface of the reinforcement, and includes the thickness of masonry face shells, mortar and grout. The following minimum cover requirements apply:

• masonry exposed to weather or earth bars larger than No. 5 (M #16) 2 in. (51 mm) No. 5 (M #16) bars or smaller 11/2 in. (38 mm)

• masonry not exposed to weather or earth 11/2 in. (38 mm)

PLACEMENT

Specification for Masonry Structures includes installation requirements for reinforcement and ties to help ensure that elements are placed as assumed in the design, and that structural performance is not compromised. These requirements also help minimize corrosion by providing for a minimum amount of masonry and grout cover around reinforcing bars, and providing sufficient clearance for grout and mortar to surround reinforcement and accessories so that stresses can be properly transferred.

To help address potential problems associated with over-reinforcing and grout consolidation, the Building Code Requirements for Masonry Structures strength design chapter contains the following requirements:

• maximum bar size No. 9 (M # 29), • nominal bar diameter not more than 1/8 the nominal member thickness (i.e., maximum No. 8 (M #25) bar in an 8-in. (203-mm)

wall) nor more than 1/4 the least clear dimension of the cell, course or collar joint where it is placed, and

• maximum area of reinforcing bars of 4% of the cell area (i.e., about 1.2 in.2, 1.6 in.2, or 2.1 in.2 for 8, 10 and 12 in. concrete masonry, respectively (774, 1032 or 1354 mm2 for 203, 254 and 305 mm units, respectively).

Reinforcing Bars Tolerances for placing reinforcing bars are: • variation from d for flexural elements (measured from the center of reinforcement to the extreme compressive face of masonry): d < 8 in. (203 mm) +1/2 in. (13 mm)

8 in. (203 mm) < d < 24 in. (610 mm) +1 in. (25 mm)

d > 24 in. (610 mm) +11/4 in. (32 mm)

• for vertical bars in walls 2 in. (51 mm) from the location along the length of the wall indicated on the project drawings.

In addition, a minimum clear distance between reinforcing bars and the adjacent face of a masonry unit of 1/4 in. (6.4 mm) for fine

grout or 1/2 in. (13 mm) for coarse grout must be maintained so that grout can flow around the bars.



DEVELOPMENT

Development length or anchorage is necessary to transfer the forces acting on the reinforcement to the grout in which it is embedded. Reinforcing bars can be anchored by embedment length, hook or mechanical device. Reinforcing bars anchored by embedment length rely on interlock at the bar deformations and on sufficient masonry cover to prevent splitting from the reinforcing bar to the free surface.

For allowable stress design, the required embedment length for reinforcement in tension is: ld = 0.0015 db Fs, but not less than 12 in. (305 mm) for bars or 6 in. (152 mm) for wires (metric: ld = 0.22 db Fs)

where: ld = embedment length of straight reinforcement, in. (mm) db = nominal diameter of reinforcement, in. (mm) Fs = allowable tensile stress in reinforcement, psi (MPa)

In addition, Section 2.1.10.3 of Building Code Requirements for Masonry Structures requires increased embedment lengths for flexural reinforcement in some cases. In concrete work, bond strength values of deformed reinforcing bars are equated to development length. The allowable stress design minimum embedment lengths are based on an allowable bond stress of 160 psi (1.10 MPa) (ref. 1).

When using strength design, the required embedment length for reinforcement in tension or compression is: ld = lde /f, but not less than 12 in. (305 mm)

where: lde = basic development length of reinforcement, in. (mm)

= 0.13 db2 fy g/K (f'm)1/2 (metric: lde = 1.5 db

2 fy g/K (f'm)1/2)

f = strength reduction factor = 0.8 fy = specified yield strength of steel, psi (MPa) g = reinforcement size factor = 1.0 for No. 3 through 5 bars (M #10 - 16); 1.4 for No. 6 and 7 bars (M #19 & 22); and 1.5 for No. 8 and 9 bars (M #25 & 29) K = the least of the masonry cover, the clear spacing between adjacent reinforcement and 5db , in. (mm) f'm = specified compressive strength of masonry, psi (MPa)

This embedment length is based on developing a minimum reinforcing steel stress of 1.25fy, similar to the requirement for welded or mechanical splices.

Standard Hooks Figure 2 illustrates the requirements for standard hooks, when reinforcing bars are anchored by hooks. Table 4 lists equivalent embedment lengths for standard hooks of various sizes.

Splices Splices are used to provide continuity of reinforcement. Tables 5 and 6 list the allowable stress design and strength design requirements, respectively, for the most commonly used lap splices including noncontact lap splices. Reinforcing bars may be spliced using lap, mechanical or welded splices.

Mechanical splices must be capable of developing at least 125% of the specified yield strength of the bar in tension or compression, as required (ref. 1). This tensile strength requirement ensures sufficient splice strength to avoid brittle failure. Mechanical splices are typically threaded reinforcing bars, joined using couplers designed for this application.

Welded splices are accomplished by butting and welding the bars. The welded splice must be strong enough to develop at least 125% of the specified yield strength of the bar in tension. All welds must conform to AWS D1.4 (ref. 14).



End-bearing splices may be used only for bars required for compression and only in members containing closed ties, closed stirrups or spirals. Building Code Requirements for Masonry Structures (ref. 1) contains requirements to ensure adequate bearing for end-bearing splices.

Joint Reinforcement Splices Joint reinforcement is typically spliced 6 in. (152 mm) to transfer shrinkage stresses. Slippage of the deformed side wires is resisted not only by the surface bond but also by the mechanical anchorage afforded by the embedded portions of the weld-connected cross wires (ref. 11).



REFERENCES

1. Building Code Requirements for Masonry Structures, ACI 530-02/ASCE 5-02/TMS 402-02. Reported by the Masonry Standards Joint Committee, 2002. 2. Manual of Standard Practice, MSP 1-01. Concrete Reinforcing Steel Institute, 2001. 3. Specification for Masonry Structures, ACI 530.1-02/ASCE 6-02/TMS 602-02. Reported by the Masonry Standards Joint Committee, 2002. 4. Standard Specification for Deformed and Plain Billet-Steel Bars for Concrete Reinforcement, ASTM A 615/A 615M-01b. ASTM International, Inc., 2001. 5. Standard Specification for Low-Alloy Steel Deformed and Plain Bars for Concrete Reinforcement, ASTM A 706/A 706M-01. ASTM International, Inc., 2001 6. Standard Specification for Masonry Joint Reinforcement, ASTM A 951-00. ASTM International, Inc., 2000. 7. Standard Specification for Stainless and Heat-Resisting Steel Wire, ASTM A 580-98. ASTM International, Inc., 1998. 8. Standard Specification for Steel Wire, Plain, for Concrete Reinforcement, ASTM A 82-01. ASTM International, Inc., 2001. 9. Standard Specification for Zinc (1987) Coating (Hot-Dip) on Iron and Steel Hardware, ASTM A 153-01a. ASTM International, Inc., 2001. 10. Standard Specification for Zinc-Coated (Galvanized) Carbon Steel Wire, ASTM A 641-98. ASTM International, Inc., 1998. 11. Structural Role of Joint Reinforcement in Concrete Masonry, TEK 12-2A, National Concrete Masonry Association, 1997. 12. Post-Tensioned Concrete Masonry Wall Construction, TEK 3-14, National Concrete Masonry Association, 2002. 13. Standard Specification for Rail-Steel and Axle-Steel Deformed Bars for Concrete Reinforcement, A 996/996M-01a. ASTM International, Inc., 2001. 14. Structural Welding Code - Reinforcing Steel, AWS D1.4. American Welding Society, 1998. 15. Standard Specification for Epoxy-Coated Steel Wire and Welded Wire Fabric for Reinforcement, ASTM A 884/884M-01. ASTM International, Inc., 2001.



Table 1—Representative Sound Levels

Loudness Decibels SoundJet plane takeoff

Deafening 110-150 Siren at 100 ft (30 m)Thunder—sonic boom

Hard rock bandVery Loud 90-100 Power lawn mower

Pneumatic jackhammerLoud 70-80 Noisy office

Average radioModerate 50-60 Normal conversation

Average homeFaint 30-40 Private office

Quiet homeVery Faint 3-20 Whisper at 4 ft (1.2 m)

Normal breathing

SOUND TRANSMISSION CLASS RATINGSFOR CONCRETE MASONRY WALLS



TEK 13-1ASound (2000)

sational tones have a frequency of approximately 500 Hz.Regarding intensity, Table 1 provides an indication of thedecibel as a measure of sound intensity.

Sounds are vibrations transmitted through air or othermediums. The speed of sound through a particular mediumdepends on both the density and the stiffness of the medium.

All solid materials have a natural frequency of vibration.If the natural frequency of a solid is at or near the frequency ofthe sound which strikes it, the solid will vibrate in sympathywith the sound, which will be regenerated on the opposite side.The effect is especially noticeable in walls or partitions thatare light, thin, or flexible. Conversely, the vibration is effec-tively stopped if the partition is heavy and rigid, as is the casewith concrete masonry walls. Then, the natural cycle of vibra-tion will be relatively slow and only sounds of low frequencywill cause sympathetic vibration. Because of its mass andrigidity, concrete masonry is especially effective in reducing thetransmission of unwanted sound.

SOUND TRANSMISSION CLASS

Sound transmission class (STC) provides an estimate ofthe performance of a wall in certain common sound insula-tion applications.

The STC of a wall is determined by comparing plottedtransmission loss values to a standard contour. Sound trans-mission loss (STL) is the decrease or attenuation in soundenergy, in dB, of airborne sound as it passes through a wall.Although STC is a convenient index of transmission loss, itmay be necessary in some cases to study the sound transmis-sion loss data across a range of frequencies. This may bedesirable in a case where the main source of noise is of oneknown frequency. In this case, the STL curve is checked toensure there is not a “hole”, or low STL value, at the particularfrequency of interest.

To determine STC, the standard curve is superimposedover a plot of the STL curve obtained by test (Figure 1) andshifted upward or downward relative to the test curve untilsome of the measured transmission loss values fall belowthose of the standard STC contour and the following condi-tions are fulfilled:

INTRODUCTION

Unwanted noise can be a major distraction, whether inthe home or the work environment. Concrete masonry wallsare often used for their ability to isolate and dissipate noise.Concrete masonry is an excellent noise control material in twoways. First, masonry walls effectively block sound transmissionover a wide range of frequencies. Secondly, concrete masonrycan effectively absorb noise thereby diminishing noise intensity.These abilities have led to the successful use of concrete masonryin applications ranging from party walls to hotel separation walls,and even highway sound walls.

Sound is characterized by its frequency and intensity.Frequency is a measure of the number of vibrations or cyclesper second. One cycle per second is defined as a hertz (Hz).Intensity is measured in decibels (dB), a relative logarithmicintensity scale. For each 20 dB increase in sound there is acorresponding tenfold increase in pressure. This logarithmicscale is particularly appropriate for sound because the percep-tion of sound by human ear is also logarithmic. For example, a10 dB sound level increase is perceived by the ear as a doublingof the loudness.

The human ear can perceive sounds as low as 16 Hz to ashigh as 20,000 Hz. However, it is most sensitive to soundsbetween 500 and 5000 Hz. Human voices speaking in conver-

Keywords: noise control, sound transmission class, soundtransmission loss, STC, STL, testing

Figure 1—Standard Contour Fitted toTransmission Loss Data

200 400 600 800 1000 3000Frequency, Hz

0

10

20

30

Tran

smis

sion

loss

, dB

1. The sum of the deficiencies (deviations below thestandard contour) are not greater than 32 dB, and

2. The maximum deficiency at a single test point is notgreater than 8 dB.

When the contour is adjusted to the highest value thatmeets the above criteria, the sound transmission class is takento be the transmission loss value read from the standardcontour at the 500 Hz frequency line. For example, the STCfor the data plotted in Figure 1 is 25.

DETERMINING STC FOR CONCRETE MASONRY

Many sound transmission loss tests have been performedon various concrete masonry walls. These tests have indicateda direct relationship between wall weight and the resultingsound transmission class—heavier concrete masonry wallshave higher STC values. As shown in Figure 2, a wide varietyof STC values is available with concrete masonry construction,depending on wall weight, wall construction, and finishes.

In the absence of test data, standard calculation methodsexist, although these tend to be conservative. Standard Methodfor Determining the Sound Transmission Class Rating forMasonry Walls, TMS 0302 (ref. 2), outlines procedures fordetermining STC values of concrete masonry walls. STC can bebased on field or laboratory testing in accordance with stan-dard test methods or on a calculation procedure. The calcula-tion is based on a best-fit relationship between wall weight andSTC based on a wide range of test results, as follows:

STC = 0.18W + 40where W = wall weight in psf

The equation is applicable to uncoated fine- or medium-textured concrete masonry. Coarse-textured units, however,may allow airborne sound to enter the wall, and thereforerequire a surface treatment to seal at least one side of the wall.Coatings of acrylic, alkyd latex, or cement-based paint, or ofplaster are specifically called out in TMS 0302, although othercoatings that effectively seal the surface are also acceptable.

The equation above also assumes the following:1. Walls have a thickness of 3 in. (76 mm) or greater.2. Hollow units are laid with face shell mortar bedding, with

Standard contour

STL dataSTC = 25

Figure 2—Concrete Masonry STC Test Results

Notes:a 57.1 psf (301 kg/m2) wall weight, test designation TL-88-

488, ref. 11b 49.2 psf (240 kg/m2) wall weight, test designation TL-88-

476, ref. 11c STC = 49: 39 psf (190 kg/m2) wall weight (lightweight),

test designation KAL 1144-1-71, ref. 12STC = 50: 48.2 psf (236 kg/m2) wall weight (normalweight), test designation TL-88-356, ref. 11STC = 52: 53 psf (259 kg/m2) wall weight (nomalweight), test designation KAL 1144-3-71, ref. 12

d 48.2 psf (236 kg/m2) wall weight of CMU only, test desig-nation TL-88-361, ref. 11

e 48.2 psf (236 kg/m2) wall weight of CMU only, test desig-nation TL-88-384, ref. 11

f 85.4 psf (417 kg/m2) wall weight of masonry only, testdesignation TL-88-431, ref. 11

Wall Construction STC

50a

49-52c

54d

64e

79f

55b

6 in. (140 mm) 100% SOLID CMU

2 COATS LATEX BLOCK SEALER

GYPSUM WALLBOARD / in. (13 mm) 1 2

BATTS INSTALLED BETWEEN

6 in. (140 mm) 75% SOLID CMU1 / in. (38 mm) GLASS FIBER1 2

WOOD FURRING

8 in. (190 mm) HOLLOW CMU

8 in. (190 mm) CMU1.5 in. (40 mm) WOOD FURRING,

/ in. (16 mm) GYPSUM BOTH SIDES

WALLBOARD, BOTH SIDES85

WALLBOARD, BOTH SIDES / in. (16 mm) GYPSUM

2 in. (50 mm) Z BARS, BOTH SIDES

8 in. (190 mm) CMU

GLASS FIBER BATTS, BOTH SIDES

85

2 / in. (65 mm) GLASS FIBER PANEL

8 in. (190 mm) CMU

RIB CMU4 in. (90 mm) SPLIT

3 / in. (90 mm) AIR SPACE1 2

21

SCREWEDWALLBOARD

TO CMU

GYPSUM / in. (16 mm) 5 8

mortar joints the full thickness of the face shell.3.Solid units are fully mortar bedded.4.All holes, cracks, and voids in the masonry that are intended

to be filled with mortar are solidly filled with mortar.If STC tests are performed, the Standard requires the

testing to be in accordance with ASTM E 90, Standard TestMethod for Laboratory Measurement of Airborne SoundTransmission Loss of Building Partitions (ref. 8) for labo-ratory testing or ASTM E 413, Standard Classification forRating Sound Insulation (ref. 6) for field testing.

DESIGN AND CONSTRUCTION

In addition to STC values for walls, other factors alsoaffect the acoustical environment of a building. For ex-ample, outside noise levels need to be considered. Lowbackground noise levels, such as exist in rural areas, mayindicate the need for partition walls to have a higher STCrequirement, since the background noise levels cannot becounted on to mask other noises.

Seemingly minor construction details can also im-pact the acoustic performance of a wall. For example,When gypsum wallboard is attached to steel furring orresilient channels, using screws that are too long willresult in the screw contacting the face of the concretemasonry substrate, which becomes an effective path forsound vibration transmission.

Standard Method for Determining the Sound Trans-mission Class Rating for Masonry Walls (ref. 2) includesrequirements for sealing openings and joints, to ensurethese gaps do not undermine the sound transmission charac-teristics of the wall. These requirements are describedbelow and illustrated in Figures 3 and 4.

Through-wall openings should be completely sealed,after first filling gaps with foam, cellulose fiber, glass fiber,ceramic fiber or mineral wool. Similarly, partial wall pen-etration openings and inserts, such as electrical boxes,should also be completely sealed.

Control joints and joints between the top of walls androof or floor assemblies should be sealed with elastomericjoint sealants. The joint space behind the sealant backing canbe filled with mortar, grout, foam, cellulose fiber, glassfiber or mineral wool (see Figure 4).

Additional considerations, not covered in TMS 0302, willalso help minimize sound transmission. For example, in apart-ment construction, floor plans that reduce the number ofcommon walls between units are preferred. “Mirror-plan”arrangements, with bedrooms located adjacent to each other,and noisy areas such as kitchens abutting each other, willgenerally result in less disturbance between neighbors. Doorand window arrangement may also have an effect on theacoustical environment. Locating apartment doors so that theyare not directly opposite each other diffuses a portion of noisethat would otherwise be transmitted directly across a hall.Windows in exterior walls should be located as far fromcommon walls as possible to help diffuse noise that maytravel from one window to another. See TEK 13-2 (ref. 4) formore information on room layouts to minimize sound trans-mission.

BUILDING CODE REQUIREMENTS

The model building codes contain requirements toregulate sound transmission for partitions that separateadjacent units in multifamily dwellings and for partitionsthat separate dwelling units from public areas, serviceareas, or commercial facilities. In the BOCA NationalBuilding Code and the appendix of the Standard BuildingCode (refs. 1, 5), all partitions serving the above purposemust have a sound transmission class of at least 45 dB forairborne noise when tested in accordance with ASTM E 90(ref. 8). The International Building Code and the Appen-dix of the Uniform Building Code (refs. 9, 10) establisha lower limit of 50 dB for the same applications.

FOAM, FIBER OR

PIPE

PIPE

MINERAL WOOL FILLSEALANTELASTOMERIC

ELASTOMERICSEALANT

ELASTOMERICSEALANT

ELASTOMERICSEALANT

ELECTRICALCONDUIT

REQUIREDSLEEVE, WHERE

MORTAR

FOAM, FIBER ORMINERAL WOOL FILL

MORTAR

MINERAL WOOL FILLFOAM, FIBER OR

ELECTRICALRECEPTACLE BOX

Figure 3—Sealing Around Penetrations and Fixtures

ELASTOMERIC SEALANT

BACKER ROD

ELASTOMERIC

MORTAR RAKEDBACK / in. (19 mm) GASKET MATERIAL

CONTROL JOINT3

4

SEALANT

Figure 4—Sealing Wall Intersections and Control Joints



REFERENCES1. BOCA National Building Code. Country Club Hills, IL: Building Officials and Code Administrators International, Inc. (BOCA),

1999.2. Standard Method for Determining the Sound Transmission Class Rating for Masonry Walls, TMS 0302-00. The Masonry

Society, 2000.3. Noise Control in Buildings, National Research Council of Canada, 1987.4. Noise Control with Concrete Masonry in Multifamily Units, TEK 13-2. National Concrete Masonry Association, 1997.5. Standard Building Code. Birmingham, AL: Southern Building Code Congress International, Inc. (SBCCI), 1999.6. Standard Classification for Rating Sound Insulation, ASTM E 413-87(1999). American Society for Testing and Materials, 1999.7. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90-00. American Society for Testing and

Materials, 2000.8. Standard Test Method for Laboratory Measurement of Airborne-Sound Transmission Loss of Building Partitions, ASTM

E 90-99. American Society for Testing and Materials, 1999.9. Uniform Building Code. Whittier, CA: International Conference of Building Officials (ICBO), 1997.10. International Building Code. Falls Church, VA: International Code Council, 2000.11. Sound Transmission Loss Measurements on 190 and 140 mm Single Wythe Concrete Block Walls and on 90 mm Cavity Block

Walls, Report for Ontario Concrete Block Association. National Research Center of Canada Report No. CR-5588.1, 1989.12. Kodaras Acoustical Laboratories, Elmhurst, NY, 1971.

Keywords: multifamily housing, noise control, noise reduc-tion coefficient, openings in walls, paints and painting,residential, sound absorption, sound transmission class

TEK 13-2 © 1997 National Concrete Masonry Association


NOISE CONTROL WITH CONCRETEMASONRY IN MULTIFAMILY HOUSING

TEK 13-2Sound (1997)

INTRODUCTION

Multifamily housing is considerably noisier than singlefamily residences. Here, the occupants of a given unit are notonly exposed to noise from the exterior and noise generated intheir own living area, but they are also exposed to noise fromoccupants of adjoining units.

Studies and surveys of occupant desires show conclu-sively that people want residences which are soundproof fromthe exterior enviroment, between rooms and between livingunits. Since it is not feasible to remove the cause of unwantedsound, designers of multifamily housing must control theacoustical environment. Concrete masonry is the economicalbuilding material which enables the designing architect orengineer to effectively respond to this challenge.

Concrete masonry is an ideal noise control material in twoways. First, masonry walls act as barriers which block soundtransmission over a wide range of frequencies. Outdoor soundsand sounds from other living units are thus reflected away byconcrete masonry walls. Secondly, concrete masonry is aneffective sound absorption matrial for absorbing noise gener-ated within a room (see Figure 1).

Three techniques are commonly used to reduce unwantedsound. The first is the elimination of the source of the noise. Inmultifamily housing, this technique would be impractical if notimpossible. The second method of reducing noise is to dimin-ish the sound level within a room by absorbing the soundinstead of reflecting it back into the room. The third method isto use sound insulating material to prevent sound waves frombeing transmitted from an adjoining area.

SOUND ABSORPTION

Sound absorption control involves minimizing soundreflection, so that the noise generated within is controlled.Sound absoption is most important in applications like assem-bly areas or concert halls. The extent of control depends on theroom surface's ability to absorb rather than reflect soundwaves. The sound absorption coefficient is an indication of thesound absorbing efficiency of a surface. A surface which couldtheoretically absorb 100% of impinging sound would have asound absorption coefficient of 1. Similarly, a surface absorb-ing 45% of incident sound would have a coefficient of 0.45.

Another designator, the noise reduction coefficient (NRC),is calculated by taking a mathematical average of the soundabsorption coefficients obtained at frequencies of 250, 500,1,000 and 2,000 cycles per second. Table 1 lists the approximateNRC values of concrete masonry.

NRC values depend on the porosity of the material and thesurface texture. More porous and open-textured surfaces areable to absorb more sound and, hence, have a higher NRC.

SOUND ISOLATION

For sound violation between dwelling units, walls aredesigned to minimize sound transmission. Unlike sound ab-sorption, for this purpose, higher density concrete tends to bemore effective than lighter weight materials.

To determine the effectiveness of wall construction as aFigure 1—Sound Reflection and Absorption Characteris-

tics of Concrete Masonry

a Applies to ungrouted single wythe walls. Grout, or other corefill materials, and finish systems will increase the wall weight, andtherefore, increase the STC.

considered to be areas of average noise, while public spacessuch as corridors, stairs, halls or service areas are consideredto have high noise levels.

SELECTION OF WALLS

In choosing the type of concrete masonry for walls,evaluate the porosity and density of the material. Soundtransmission loss increases with unit weight and decreaseswith porosity. Transmission loss characteristics of unpainted,open textured units can be increased by plastering or painting.At the same time, sealing the pores results in a correspondingreduction in the sound absorption (NRC) of the block.

It is sometimes thought that by using open texturedconcrete block, both sound absorption and sound insula-tion can effectively be obtained, although this is generallynot completely achievable. There are instances, however,when the designer may wish to use both properties ofconcrete block to advantage. In multifamily housing thedesigner can consider using concrete masonry partitionsto separate public areas such as stairwells and corridorsfrom adjacent living areas. In this application the opentextured surface of the concrete block is left unpainted toretain sound absorption and to reduce the echo fromcorridor sounds. Sound transmission reduction is achievedby painting or plastering the surface of the living area onthe opposite side of the partition. A similar technique,which affords sound absorption on both sides of the wall,

means of sound isolation, a steady sound is generated andmeasured on one side of a wall, and the transmitted sound ismeasured in an adjacent room. The difference in sound levelsindicates the transmission loss of the wall. For example, if agenerated sound level of 80 dB is observed in one room, and30 dB measured in the adjacent room, the reduction in soundintensity due to the intervening wall is 50 dB. The wall is saidto have a 50 dB sound transmission loss. The higher thetransmission loss of a wall, the better it functions as a soundbarrier.

Arithmetic averages of sound transmission loss at se-lected frequencies were extensively used in the past to rate theeffectiveness of walls. The classification method was some-times unreliable, however, because a good average could beascribed to a wall that performed poorly at a particular fre-quency. The American Society for Testing and Materialsprovides a test standard, ASTM E 90, to provide a soundreduction rating by a single number called sound transmissionclass (STC). A detailed explanation of determining STC ratingsis published in NCMA TEK 13-1 (ref. 2 ).

STC ratings for concrete masonry walls can be easilyestimated using the equation:

STC = 23 w0.2

where w = wall weight in lb/ft2

Some representative STC values are listed in Table 2.Model building codes provide minimum STC ratings for

partitions that separate adjacent units in multifamily dwellingsand similar partitions that separate a dwelling unit from publicand service areas (see Table 3). Generally, living units are

a May be reduced to 45 if field tested.

Table 2—Typical STC Ratings of Concrete Masonry WallsNominal

wall thickness, in.Density of

concrete, pcfSTCa

6 105135

4345

8 105135

4548

10 105135

4750

12 105135

4951

Table 1—Approximate Noise Reduction CoefficientsNCR for Unpainted CMU Wall

SurfaceTextureCoarse Medium Fine

Lightweight concretemasonryNormal weight concretemasonry

0.50

0.28

0.45

0.27

0.40

0.26

NRC for Painted Lightweight CMU WallPaint, application Coats Surface Texture

Coarse Medium FineAny, sprayed

Oil, brushed

Latex, brushed

Cement, brushed

12121212

0.450.400.400.230.350.230.200.05

0.410.360.360.210.320.210.180.05

0.360.320.320.180.280.180.160.04

NRC for Painted Normal Weight CMU WallPaint, application Coats Surface Texture

Coarse Medium FineAny, sprayed

Oil, brushed

Latex, brushed

Cement, brushed

12121212

0.250.220.220.130.200.130.110.03

0.240.220.220.130.190.130.110.03

0.230.210.210.120.180.120.100.03

Table 3—Sound Transmission Class Requirements

Location of partitionSTC

UBC BOCA SBC

Living unit to living unit(average noise)

Living unit to public spaceand service area(high noise)

50a

50a

45

45

45

45

as well as sound reduction, uses open textured units in a cavitywall with back plastering on the inside face of one of the wythes.

DESIGN AND CONSTRUCTION

Early in the design stages, a detailed noise survey shouldbe conducted to determine the outside noise level and theanticipated background noise level in completed living units.A building layout can then be developed which will effectivelyreduce the noise transmission from one area to another.

All of the design elements that are employed in soundcontrol—proper layout, selection of walls, etc., can be madeineffective through poor or improper construction. Soundleakage will occur through any opening in a wall. An improperlyfitted corridor door is a prime source of sound leakage, as wellas openings around ducts, piping, and electrical outlets whichare improperly fitted or sealed. A crack just 0.007 in. (0.178 mm)wide along the top of a 12.5 ft (3.8 m) wall would let through asmuch sound as a 1 in.2 (645 mm2) hole.

A good acoustical design takes the following into consid-eration. The details below show six ways noise transmissioncan be reduced.

PLAN INLINE RATHER THANCUBICLE BUILDINGS

In a cubicle plan, each apartment may have up to 3 commonwalls. In an in-line plan with halls between every other apart-ment, each apartment will have only one common wall totransmit sound.

USE MIRROR FLOOR PLANS

Generally this arrangement will place adjacent apartmentsso that quieter areas (bedrooms) abut, and noisy areas (kitch-ens) are next to similar noisy areas.

STAGGER THE DOORS OF APARTMENTSOPENING ONTO THE SAME HALL

Sound travels most effectively in straight lines. Every timeit changes direction, some of it is asorbed and some diffused.

PLACE WINDOWS AS FARFROM COMMON WALL AS POSSIBLE

The closer windows are to each other, the more sound willpass from one window to the other. Simply separating windowswill stop much of this sound.

OFFSET MEDICINE CABINETS INDOUBLE BATHROOM PARTITIONS

Medicine cabinets should be offset from one another andeither backed up with solid material or surface mounted on thewall. Cabinets placed back-to-back will transmit almost asmuch noise as an opening.

NATIONAL CONCRETE MASONRY ASSOCIATION To order a complete TEK Manual or TEK Index,2302 Horse Pen Road, Herndon, Virginia 20171-3499 contact NCMA Publications (703) 713-1900

DUCTS CARRY NOISEFROM ONE ROOM TO ANOTHER

REFERENCES

1. Standard Specification for Loadbearing Concrete Ma-sonry Units, ASTM C 90-96a. American Society for Test-ing and Materials, 1996.

2. Sound Transmission Class Ratings for Concrete Ma-sonry Walls, TEK 13-1. National Concrete Masonry As-sociation, 1990.

3. BOCA National Building Code. Country Club Hills, IL:Building Officials and Code Administrators International,Inc. (BOCA), 1996.

4. Standard Building Code. Birmingham, AL: SouthernBuilding Code Congress International, Inc. (SBCCI), 1994.

5. Uniform Building Code. Whittier, CA: International Con-ference of Building Officials (ICBO), 1997.

14-1A: SECTION PROPERTIES OF CONCRETE MASONRY WALLS

INTRODUCTION

Engineered design of concrete masonry walls uses section properties to determine strength, stiffness and deflection characteristics. These design philosophies are summarized in Allowable Stress Design of Concrete Masonry and Strength Design of Concrete Masonry (refs. 3, 4).

SECTION PROPERTIES

Tables 1 through 10 (click to view all Tables) summarize section properties of grouted and ungrouted 4, 6, 8, 10, 12, 14 and 16 in. (102, 152, 203, 254, 305, 356 and 406 mm) wide concrete masonry walls, based on the following assumptions:

� standard unit dimensions are based on the minimum face shell and web thickness requirements of Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90 (ref. 2) as shown in Figure 1 (except as noted in Tables 8, 9 and 10 (click to view all Tables)),

� each unit has square ends and two square cores, � the nominal face dimensions of all units are 16 in. long by 8 in. high (406 by 203 mm), � all units have a symmetrical cross-section, � all mortar joints are 3/8 in. (9.5 mm) thick, and

� all mortar joints are the same depth as the thickness of the face shell or web on which they are placed.


Keywords: allowable stress design, area (net vs. gross), moment of inertia, radius of gyration, reinforced concrete masonry, reinforced properties, section modulus, section properties, strength design, structural properties

Page 1 of 414-1A: Section Properties of Concrete Masonry Walls


of 414-1A: Section Properties of Concrete Masonry Walls


The tables include both net and average section properties. The net section properties (An, In and Sn) are calculated based on the minimum net cross-sectional area of an assemblage. These values are related to the critical section when determining stresses due to an applied load (ref. 1). Average section properties (Aavg, Iavg, Savg and ravg) correspond to an average cross-sectional area of an assemblage. Average section properties are used to determine stiffness or deflection due to applied loading (ref. 1). The net and average horizontal section properties are listed in Tables 1a, 2a (click to view all Tables), etc. while vertical section properties are listed in Tables 1b, 2b (click to view all Tables), etc. For vertically spanning walls, horizontal section properties are calculated along a horizontal axis parallel to the plane of the masonry (axis X-X in Figure 2). For horizontally spanning walls, vertical section properties are calculated along a vertical axis parallel to the plane of the masonry (axis Y-Y in Figure 2).

In addition to section properties based on the standard unit dimensions shown in Figure 1, Tables 8 and 9 (click to view all Tables) list section properties of walls constructed using 8-inch (203-mm) units with thickened face shells. These units are often specified to achieve higher fire ratings. Table 10 (click to view all Tables) lists section properties of walls constructed using 12-in. (305-mm) units with 11/4 in. (32 mm) face shells. These units are permitted by ASTM C 90 (ref. 2) when allowable design loads are reduced in proportion to the reduction in face shell thickness.

REFERENCES

1. Building Code Requirements for Masonry Structures, ACI 530-02/ASCE 5-02/TMS 402-02. Reported by the Masonry Standards Joint Committee, 2002.

2. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90-02. ASTM International, 2002.

3. Allowable Stress Design of Concrete Masonry, TEK 14-7A. National Concrete Masonry Association, 2002.

4. Strength Design of Concrete Masonry, TEK 14-4A. National Concrete Masonry Association, 2002.

5. Concrete Masonry Design Tables, TR 121. National Concrete Masonry Association, 2000.



TEK 14-22Structural (2003)


TEK 14-22 © 2003 National Concrete Masonry Association

Construction of masonry wall systems is possible without the use of mortar. The use of standard CMU units laid dry and subsequently surface bonded with fi ber reinforced surfaced bonding cement has been well documented in the past. (ref. 16) With the use of specially fabricated concrete masonry units known as “dry-stack units,” construction of these mortarless systems is simple, easy and cost effective. This TEK describes the construction and engineering design of such mor-tarless wall systems. The provisions of this TEK apply to both specialty units manufactured specifi cally for dry-stack construction and con-ventional concrete masonry units with the following system types: • Grouted, partially grouted or surface bonded • Unreinforced, reinforced, or prestressed Note that dry-stacked prestressed systems are available that do not contain grout or surface bonding. The provisions of this

TEK do not apply to such systems due to a difference in design section properties (ref 8). Specially designed units for dry-stack construction are available in many different confi gurations as shown in Figure 1. The latest and most sophisticated designs incorporate face shell alignment features that make units easier and faster to stack plumb and level. Other units are fabricated with a com-bination of keys, tabs or slots along both horizontal and ver-tical faces as shown in Figure 1 so that they may interlock easily when placed. Physical tolerances of dry-stack concrete units are limited to ±1/16 in. (1.58 mm.) which precludes the need for mortaring, grinding of face shell surfaces or shim-ming to even out courses during construction. Interlocking units placed in running bond resist fl exural and shear stresses resulting from out-of-plane loads as a result of the keying action: (a) at the top of a web with the recess in the web of the unit above, (b) at two levels of bearing surface along each face shell at the bed joint, and (c) between adjacent blocks along the head joint. The fi rst of these two interlocking mechanisms also ensures vertical alignment of blocks. The interlocking features of dry-stack units improve alignment and leveling, reduce the need for skilled labor and reduce construction time. Floor and roof systems can be sup-ported by mortarless walls with a bond beam at the top of the

DESIGN AND CONSTRUCTION OF DRY-STACK MASONRY WALLS

Keywords: allowable stress design, architectural details, bond beams, composite wall, construction details, construc-tion techniques, dry-stack, lintels, mortarless masonry, pre-stressed masonry, reinforced masonry, surface bonding

INTRODUCTION

Figure 1–– Dry-Stack Masonry Units

Specialty Units for Dry-Stack Masonry Standard CMUFace shell aligning

slotted systemFace shell aligning

slotted / tabbed systemNon-face shell aligning

systemsNon-face shell aligning

standard CMU

wall which expedites the construction process. Wall strength and stability are greatly enhanced with grouting which provides the necessary integrity to resist forces applied parallel, and transverse to, the wall plane. Ver-tical alignment of webs ensures a continuous grout column even when the adjacent cell is left ungrouted. Grouting is necessary to develop fl exural tensile stress normal to the bed joints, which is resisted through unit-mortar bond for tradi-tional masonry construction. Strength of grouted dry-stack walls may also be enhanced by traditional reinforcement, prestressing, post-tensioning or with external fi ber-reinforced surface coatings (surface bonding) as described in the next section. Typical applications for mortarless concrete masonry include basement walls, foundation walls, retaining walls, exterior above-grade walls, internal bearing walls and par-titions. Dry-stack masonry construction can prove to be a cost-effective solution for residential and low-rise commer-cial applications because of it’s speed and ease of construc-tion, strength and stability even in zones of moderate and high seismicity. More information on design and construc-tion of dry-stack masonry can be found in Reference 5.

CONSTRUCTION

Dry-stack concrete masonry units can be used to con-struct walls that are grouted or partially grouted; unrein-forced, reinforced or prestressed; or surface bonded. With each construction type, walls are built by fi rst stacking con-crete masonry units. For unreinforced construction as shown in Figure 2a, grouting provides fl exural and shear strength to a wall system. Flexural tensile stresses due to out-of-plane bending are resisted by the grout cores. Grout cores also interlace units placed in running bond and thus provide resistance to in-plane shear forces beyond that provided by friction devel-oped along horizontal joints. Grout cores can also be rein-forced to increase fl exural strength. Reinforcement can be placed vertically, in which case only those cells containing reinforcement may be grouted as shown in Figure 2b, as well as horizontally, in which case the masonry must be fully grouted. Another version is to place vertical prestressing tendons in place of reinforce-ment. Vertical axial compressive stress, applied via the ten-dons, increases fl exural and shear capacity. Tendons may be bonded to grout, or unbonded, based upon the design. Place-ment of grout may be optional. Horizontally reinforced bond beam lintels can be created using a grout stop beneath the unit to contain grout. As an alternative to reinforcing or prestressing, wall surfaces may be parged (coated) with a fi ber-reinforced sur-face bonding cement/stucco per ASTM C887(ref. 14) as illustrated in Figure 2c. This surface treatment, applied to both faces of a wall, bonds concrete units together without the need for grout or internal reinforcement. The parging material bridges the units and fi lls the joints between units to provide additional bonding of the coating to the units through keying action. The compressive strength of the

Figure 2–– Basic Dry-Stack Masonry Wall Types

a. Unreinforced, fully grouted wall

b. Reinforced, fully or partially grouted wall

c. Surface bonded wall

Dry-stack concretemasonry units

Grout in all cores

dry-stack concretemasonry units

Grouted cores with vertical reinforcing bars

Dry-stack concretemasonry units

Fiber-reinforced sur-face bonding cement parged onto both sides

parging material should be equal to or greater than that of the masonry units.

Laying of Units The fi rst course of dry-stack block should be placed on a smooth, level bearing surface of proper size and strength to ensure a plumb and stable wall. Minor rough-ness and variations in level can be corrected by setting the fi rst course in mortar. Blocks should be laid in running bond such that cells will be aligned vertically.

Grout and Reinforcement Grout and grouting procedures should be the same as used in conventional masonry construction (ref. 1, 10) except that the grout must have a compressive strength of at least 2600 psi (190 MPa) at 28 days when tested in accordance with ASTM C 1019 (ref.12). Placement of grout can be accomplished in one lift for single-story height walls less than 8 ft (2.43 m). Grout lifts must be consolidated with an internal vibrator with a head size less than 1 in. (25 mm).

Vertical Reinforcing As for conventional reinforced masonry construc-tion, good construction practice should include placement of reinforcing bars around door and window openings, at the ends, top and bottom of a wall, and between intersect-ing walls. Well detailed reinforcement such as this can help enhance nonlinear deformation capacity, or ductility, of masonry walls in building systems subjected to earth-quake loadings - even for walls designed as unreinforced elements. Additional information on conventional grout-ing and reinforced masonry wall can be found in TEK 9-4 and TEK 3-3A (refs. 9 & 6).

Pre-stressed Walls Mortarless walls can also be prestressed by placing vertical tendons through the cores. Tendons can be anchored within the concrete foundation at the base of a

wall or in a bottom bond beam and are tensioned from the top of a wall.

Surface Bonded Walls For walls strengthened with a surface bonding, a thin layer of portland cement surface bonding material should be troweled or sprayed on to a wall surface. The thickness of the surface coating should be at least 1/8 in. (3.2 mm.) or as required by the material supplier.

ENGINEERING PROPERTIES Walls constructed with mortarless masonry can be engineered using conventional engineering principles. Existing building code recommendations such as that pro-duced by the building code (ref. 1) can serve as reference documents, but at the time of this printing it does not address mortarless masonry directly. It is thus considered an alternate engineered construction type. The Interna-tional Building Code (ref. 7) does list allowable stresses based on gross-cross-sectional area for dry-stacked, sur-face-bonded concrete masonry walls. These values are the same as presented in TEK 3-5A (ref. 16). Suggested limits on wall or building height are given in Table 1. Test data (refs. 2, 3 and 4) have shown that the strength of dry-stack walls exceeds the strength require-ments of conventional masonry, and thus the recommended allowable stress design practices of the code can be used in most cases. When designing unreinforced, grouted masonry wall sections, it is important to deduct the thick-ness of the tension side face shell when determining the section properties for fl exural resistance.

Unit and Masonry Compressive Strength Units used for mortarless masonry construction are made of the same concrete mixes as used for conventional masonry units. Thus, compressive strength of typical units could vary between 2000 psi (13.79MPa) and 4000 psi. (27.58 MPa) Standard Methods of Sampling and Testing Concrete Masonry Units (ref. 11) can be referred to for determining strength of dry-stack units. Masonry compressive strength f’

m can conserva-

tively be based on the unit-strength method of the build-ing code (ref . 15), or be determined by testing prisms in accordance with ASTM C1314 (ref. 4). Test prisms can be either grouted or ungrouted depending on the type of wall construction specifi ed.

* Laterally supported at each fl oor

Table 1 –– Summary of Wall Heights for 8” (203 mm) Dry-stacked Units (ref. 5)

Construction Type

Basement walls

Cantilevered retaining walls

Single-story buildings

Multi-story buildings*

Grouted unreinforced

Groutedreinforced

Surface bonded

8’ - 0”(2.44m)

5’ -0”(1.52m)15’ -0”(4.57m)

10’ - 8”(3.25m)

8’ -8”(2.64m)

20’ -0”(6.10m)

8’ - 0”(2.62m)

5’ 4”(4.88m)16’ -0”(4.88m)

3 storiesless than 32’-8”

(9.96m) in height

4 storiesless than 40’ -8” (12.4m) in height

2 storiesless than 20’ -0” (6.10m) in height

Solid Grouted, Unreinforced ConstructionOut-of-Plane & In-Plane Allowable Flexural Strength Because no mortar is used to resist fl exural tension

as for conventional masonry construction, fl exural strength

of mortarless masonry is developed through the grout, rein-

forcement or surface coating. For out-of-plane bending of

solid grouted walls allowable fl exural strength can be esti-

mated based on fl exural tensile strength of the grout per

Equation 1.

M = ( f a + F

t ) S

g Equation 1

Consideration should be given to the reduction in

wall thickness at the bed joints when estimating geometri-

cal properties of the net effective section.

Correspondingly, fl exural strength based on masonry

compressive stress should be checked, particularly for

walls resisting signifi cant gravity loads, using the unity

equation as given below.

f

a f

b

F a F

b + ≤ 1 Equation 2

Buckling should also be checked. (Ref. 8)

In-Plane Shear Strength Shear strength for out-of-plane bending is usually

not a concern since fl exural strength governs design for

this case. For resistance to horizontal forces applied paral-

lel to the plane of a wall, Equation 3 may be used to esti-

mate allowable shear strength.

Ib Q

V = Fv Equation 3

Fv is the allowable shear strength by the lesser of the

three values given in Equation 4.

Fv = 1.5 f ‘

m

Fv = 120 psi

Fv = 60 psi + 0.45

Nv

An Equation 4

Grouted, Reinforced Construction Mortarless masonry that is grouted and reinforced

behaves much the same as for conventional reinforced and

mortared construction. Because masonry tensile strength

is neglected for mortared, reinforced construction, fl exural

mechanisms are essentially the same with or without the

bed joints being mortared provided that the units subjected

to compressive stress are in good contact. Thus, allow-

able stress design values can be determined using the same

assumptions and requirements of the MSJC code. (ref.1)

Out-of-Plane & In-Plane Allowable Flexural Strength Axial and fl exural tensile stresses are assumed to be

resisted entirely by the reinforcement. Strains in reinforce-

ment and masonry compressive strains are assumed to vary

linearly with their distance from the neutral axis. Stresses

in reinforcement and masonry compressive stresses are

assumed to vary linearly with strains. For purposes of

estimating allowable fl exural strengths, full bonding of

reinforcement to grout are assumed such that strains in

reinforcement are identical to those in the adjacent grout.

For out-of-plane loading where a single layer of ver-

tical reinforcement is placed, allowable fl exural strength

can be estimated using the equations for conventional rein-

forcement with the lower value given by Equations 5 or 6.

Ms = A

sF

s jd Equation 5

Mm = 0.5F

b jkbd2 Equation 6

In-Plane Shear Strength Though the MSJC code recognizes reinforced

masonry shear walls with no shear, or horizontal reinforce-

ment, it is recommended that mortarless walls be rein-

forced with both vertical and horizontal bars. In such case,

allowable shear strength can be determined based on shear

reinforcement provisions (ref. 1) with Equations 7, 8 and

9.

V = bdF

v Equation 7

Where Fv is the masonry allowable shear stress per

Equations 8 or 9.

Vd 2

Vd

M 1 M M for ≤ 1 Fv = (4- ) f ’

m <(120-45 ) psi

Vd

Equation 8

for ≥ 1 Fv = 1.5 f ’

m < 75 psi Vd

M

Equation 9

Solid Grouted, Prestressed Construction Mortarless masonry walls that are grouted and pre-stressed can be designed as unreinforced walls with the prestressing force acting to increase the vertical compres-sive stress. Grout can be used to increase the effective area of the wall. Flexural strength will be increased because of the increase in the f

a term in Equation 1. Shear strength

will be increased by the Nv term in Equation 4.

Because the prestressing force is a sustained force, creep effects must be considered in the masonry. Research on the long-term behavior of dry-stacked masonry by Mar-zahn and Konig (ref. 8) has shown that creep effects may be accentuated for mortarless masonry as a result of stress concentrations at the contact points of adjacent courses. Due to the roughness of the unit surfaces, high stress con-centrations can result which can lead to higher non-propor-tional creep deformations. Thus, the creep coeffi cient was found to be dependent on the degree of roughness along bed-joint surfaces and the level of applied stress. As a result, larger losses in prestressing force is probable for dry-stack masonry.

Surface-Bonded Construction Dry-stack walls with surface bonding develop their strength through the tensile strength of small fi berglass fi bers in the 1/8” (3.8mm) thick troweled or surface bonded cement-plaster coating ASTM C-887(Ref. 14). Because no grouting is necessary, fl exural tension and shear strength are developed through tensile resistance of fi berglass fi bers applied to both surfaces of a wall. Test data has shown that surface bonding can result in a net fl exural tension strength on the order of 300 psi.(2.07 MPa) Flexural capacity, based on this value, exceeds that for conventional, unrein-forced mortared masonry construction, therefore it is con-

sidered conservative to apply the desired values of the code (ref. 1) for allowable fl exural capacity for portland cement / lime type M for the full thickness of the face shell.

Out-of-Plane and In-Plane Flexural Strength Surface-bonded walls can be considered as unrein-forced and ungrouted walls with a net allowable fl exural tensile strength based on the strength of the fi ber-reinforce-ment. Flexural strength is developed by the face shells bonded by the mesh. Allowable fl exural strength can be determined using Equation 1 with an F

t value deter-

mined on the basis of tests provided by the surface bonding cement supplier. Axial and fl exural compressive stresses must also be checked per Equation 2 considering again only the face shells to resist stress.

Surface Bonded In-Plane Shear Strength In-plane shear strength of surface-bonded walls is attributable to friction developed along the bed joints resulting from vertical compressive stress in addition to the diagonal tension strength of the fi ber coating. If the enhancement in shear strength given by the fi ber reinforced surface parging is equal to or greater than that provided by the mortar-unit bond in conventional masonry construc-tion, then allowable shear strength values per the MSJC code (ref. 1)may be used. In such case, section properties used in Equation 3 should be based on the cross-section of the face shells.

Figure 3 - A Mortarless Garden Wall Application Figure 4 - A Residential, Mortarless, Single-Family Basement - Part of a 520 Home Development

REFERENCES 1. Building Code Requirements for Masonry Structures), ACI 530-02/ ASCE 5-02/TMS 402-02. Reported by the Masonry Standards Joint Committee (MSJC), 2002.2. Drysdale, R.G., Properties of Dry-Stack Block, Windsor, Ontario, July 1999.3. Drysdale, R.G., Properties of Surface-Bonded Dry-Stack Block Construction, Windsor,Ontario, January 2000.4. Drysdale, R.G., Racking Tests of Dry-Stack Block, Windsor, Ontario, October 2000.5. Drysdale, R.G., Design and Construction Guide for Azar Dry-Stack Block Construction,JNE Consulting, Ltd., February 2001.6. Grout for Concrete Masonry, TEK 9-4. National Concrete Masonry Association, 2002.7. 2000 International Building Code, Falls Church, VA. International Code Council, 2000.8. Marzahn, G. and G. Konig, Experimental Investigation of Long- Term Behavior of Dry-Stacked Masonry, Journal of The Masonry Society, December 2002, pp. 9-21.9. Reinforced Concrete Masonry Construction, TEK 3-3A. National Concrete Masonry Association, 2001.10. Specifi cation for Masonry Structures, ACI 530.1-02/ASCE 6-02/ TMS 602-02. Reported by the Masonry Standards Joint Committee (MSJC), 2002.11. Standard Methods of Sampling and Testing Concrete Masonry Units, ASTM C140-02a, ASTM International, Inc. , Philadelphia, 2002.12. Standard Method of Sampling and Testing Grout, ASTM C1019-02, ASTM International, Inc., Philadelphia, 2002.13. Standard Specifi cation for Grout for Masonry, ASTM C 476-02. ASTM International, Inc., 200214. Standard Specifi cation for Packaged, Dry, Combined Materials for Surface Bonding Mortar, ASTM C 887-79a (2001). ASTM Interna tional, Inc., 2001.15. Standard Test Method for Compressive Strength of Masonry Assem blages, ASTM C1314-02a, ASTM International, Inc., Philadelphia, 2002.16. Surface Bonded Concrete Masonry Construction, TEK 3-5A. National Concrete Masonry Association, 1998.

NOTATION

An net cross-sectional area of masonry, in2 (mm2)

As effective cross-sectional area of reinforcement, in2 (mm2)

b width of section, in. (mm)d distance from extreme compression fi ber centroid of tension rein forcement, in. (mm)F

a allowable compressive stress due to axial load only, psi (MPa)

Fb allowable compressive stress due to fl exure only, psi (MPa)

Fs allowable tensile or compressive stress in reinforcement, psi (MPa)

Ft fl exural tensile strength of the grout, psi(MPa)

Fv allowable shear stress in masonry psi (MPa)

fa calculated vertical compressive stress due to axial load, psi (MPa)

fb

calculated compressive stress in masonry due to fl exure only, psi (MPa)f’

specifi ed compressive strength of masonry, psi (MPa)

I moment of inertia in.4 (mm4)j ratio of distance between centroid of fl exural compressive forces and centroid of tensile forces to depth, dk ratio of the distance between compression face of the wall and neu tral axis to the effective depth dM maximum moment at the section under consideration, in.-lb (N-mm)N

v compressive force acting normal to the shear surface, lb (N)

Q fi rst moment about the neutral axis of a section of that portion of the cross section lying between the neutral axis and extreme fi ber in.3 (mm3)S

g section modulus of uncracked net section in.3 (mm3)

V shear force, lb (N)



14-2: REINFORCED CONCRETE MASONRY

Introduction

Structural elements constructed of reinforced concrete masonry effectively resist applied loads through the combined tensile strength of reinforcement and the compressive strength of masonry. The benefits of incorporating reinforcement are improved ductility, structural integrity, and greater resistance to flexural and shear stresses. Walls, columns, pilasters, and beams can be designed to resist dead, live, wind, seismic, and lateral earth pressure loads using the combined capabilities of masonry and reinforcement.

Reinforced concrete masonry walls are used extensively in most structural applications—warehouses, institutional buildings, retaining walls, shear walls and load-bearing walls in multistory hotel and apartments. They provide an economical system of construction, particularly in localities or in building configurations requiring high lateral load resistance.

Materials

Materials used for reinforced masonry—units, mortar, grout, and steel reinforcement, are governed by specifications that are referenced in building codes. Applicable specifications for these materials are listed in Table 1.

Units—Reinforced concrete masonry is constructed of hollow units, solid units, or a combination of both. Single wythe walls are constructed of hollow units with vertical reinforcement and grout placed in designated cores of the block. Horizontal reinforcement, such as reinforcing bars grouted into bond beams, or joint reinforcement placed in mortar joints, is also often use d. Multi-wythe walls are built with either hollow or solid units with grout and reinforcement in the space between wythes.

Units must be laid up so that the vertical spaces to be grouted provide a continuous, unobstructed opening to accommodate grout and reinforcement. Some projects require reinforcement to be in place before masonry work is begun. These requirements have resulted in the development of open-end block shapes which are designed to be placed around the reinforcement. Some of these shapes are illustrated in Figure 1.


Keywords: allowable stress, allowable stress design, ASTM specifications, construction techniques, flexural strength, grout, grouting, inspection, load-bearing walls, mortar, reinforced concrete masonry, shear walls, sizes and shapes of concrete masonry, strength design, structural properties

Table 1—Standard Material Specifications

Concrete Masonry Units ASTM C 90 Load-bearing Concrete Masonry Units UBC 21-4 Hollow and Solid Load-bearing Concrete Masonry Units Mortar ASTM C 270 Mortar for Unit Masonry UBC 21-15 Mortar for Unit Masonry Grout ASTM C 476 Grout for Masonry UBC 21-14 Grout for Masonry Aggregates ASTM C 144 Aggregate for Masonry Mortar ASTM C 404 Aggregates for Masonry Grout Reinforcement ASTM A 82 Steel Wire, Plain ASTM A 615 Deformed and Plain Billet-Steel Bars ASTM A 616 Rail-Steel Deformed and Plain Bars ASTM A 617 Axle-Steel Deformed and Plain Bars

Page 1 of 814-2: Reinforced Concrete Masonry


Mortar—Ingredients for masonry mortar are governed by applicable product specifications. Mortar types are generally specified to comply with ASTM C 270 (ref. 5). Mortar is governed by either of two alternative specifications:

1. the proportion specification prescribes the parts by volume of each ingredient required to provide a specific mortar type 2. the property specification allows approved materials to be mixed in controlled percentages as long as the resultant laboratory prepared mortar meets prescribed compressive strength, water retention, and air content requirements.

Mortar types M, S, and N are permitted for construction of reinforced concrete masonry. Building codes (refs. 2, 7) require the use of Type S or M mortar in seismic zones 3 and 4.

Grout—Ingredients for grout used in masonry construction include cementitious materials, aggregates, and hydrated lime. ASTM specifications contain requirements for proportions for each of these ingredients. However, it is typical practice to specify compressive strength based on design requirements rather than specifying proportions of each ingredient.

When grout is placed in a masonry wall, water is absorbed into the masonry units, reducing the volume of grout. The effects of grout volume loss may be minimized by reconsolidation before the grout starts to set. Expansive grout admixtures are sometimes recommended in addition to consolidation and reconsolidation to reduce voids in the grout. These materials are added at the job site, and cause the grout to expand slightly after placement, which compensates for volume reduction due to loss of water.

Steel Reinforcement—The two principal types of reinforcement used in reinforced masonry are deformed steel bars and horizontal wire joint reinforcement. Standards for the most commonly used types of reinforcement are listed in Table 1.

Construction

Placement of hollow units for reinforced concrete masonry construction requires the following considerations:

• Vertical cores to be grouted are constructed so that a continuous, unobstructed opening of approved dimensions is maintained for proper placement of reinforcement and grout. • Care should be taken to minimize mortar protrusions into the spaces to be grouted. • When hollow unit walls are not fully grouted, mortar is placed on those cross webs adjacent to the cores to be grouted, to confine grout to specified locations. • Vertical reinforcement is secured in its proper location by the use of bar positioners or by tying vertical and horizontal bars together. • Metal lath, or other suitable material, is used in partially grouted masonry below bond beam courses to confine grout to specified locations.

Placement of steel reinforcement in its specified location is critical to the performance of reinforced masonry. The flexural resistance of reinforced masonry is based on the element's effective depth, d, which is the distance from the compressive face of the masonry to the centerline location of the tensile reinforcement.

Building codes contain allowable tolerances for placement of reinforcement in walls and flexural elements, and tolerances for the distance between vertical bars along the length of a wall. A summary of tolerance requirements is contained in Table 2.

ASTM A 706 Low-Alloy Steel Deformed Bars ASTM A 767 Galvanized Steel Bars ASTM A 775 Epoxy-Coated Reinforcing Steel Bars UBC 21-10 Joint Reinforcement for Masonry

Table 2—Tolerances For Placement of Reinforcement

Placement of reinforcement Flexural members 1/2 in. (13 mm) for d 8 in. (203 mm)

1 in. (25 mm) for d > 8 in. (203 mm) but 24 in. (610mm) ........................... 1 1/4 in. (32 mm) for d > 24 in. (610 mm) Walls (vertical bars).................. 2 in. (51 mm) along the length of the wall Clear spacing between bars and face of unit Fine grout........................... 1/4 in. (6.4 mm) Coarse grout ........................ 1/2 in. (13 mm) Minimum cover joint reinforcement



In addition to allowable tolerances, codes prescribe requirements for lap splicing and minimum permissible space between reinforcement and adjacent masonry units for fine and coarse grouts to ensure that grout completely surrounds and bonds to the reinforcement.

Low Lift Grouting—Methods of placing grout in concrete masonry elements are high lift and low lift grouting. The construction sequence of low lift grouting is as follows:

• Build the masonry to scaffold height, placing horizontal reinforcement as the wall is laid up. Low lift grouting procedures limit the maximum height of masonry to 5 ft (1.5 m) prior to grouting. When a grout pour coincides with a bond beam course, an additional course of masonry should be placed above the bond beam to permit grouting the bond beam in one operation. The grout pour should then extend a minimum of 1/2 in. (13 mm) above the bond beam course.

• Place vertical reinforcement where required, ensuring that cavities containing reinforcement have a continuous unobstructed cross section complying with Table 3.

• Place grout of fluid consistency in those cavities which contain properly positioned reinforcing bars and all other cavities required to be grouted. • Consolidate the grout with a vibrator (grout pours 12 in. (305 mm) or less may be consolidated using a puddling stick). • Repeat the operation at the next higher level. Low lift grouting requires no special concrete block shapes or special equipment.

Methods of delivering grout to the wall include hand bucketing, pumping, or the use of a concrete bucket with a spout to direct the grout into the cores, whichever is most advantageous to the contractor. Complete consolidation of grout is accomplished by vibrating or puddling each lift, while penetrating into the previous lift.

A grout lift should not terminate at a mortar bed joint nor where horizontal reinforcing bars are placed. A grout key between lifts, located at least 1/2 in. (13 mm) below the mortar joint, ensures adequate shear transfer. One course may be laid above the lift height to obtain proper grout coverage of horizontal reinforcing, and the grout poured to a height approximately 1/2 in. (13 mm) above the bed joint. The final lift is poured to the top of the wall.

High Lift Grouting—On larger projects, grouting is often delayed until walls are built to story height or to the full height of the wall. Grout is then placed into the wall in several succeeding 5 ft (1.5 m) maximum lifts. This procedure is referred to as high lift grouting.

There are several advantages of high lift grouting on larger projects. Vertical steel can be placed after the wall is erected; its location can be checked by the inspector; and the grout can be transit-mixed and placed by a grout pump or concrete bucket within a relatively short time. Cleanout openings of sufficient size for removal of mortar droppings and other debris must be provided at the bottom of all vertical cavities containing reinforcement.

Horizontal reinforcing bars are positioned as the wall is erected. Vertical bars may be installed prior to laying masonry or may be inserted from the top of the wall after the masonry is placed to story height. Vertical bars should be held in position at intervals not exceeding 200 bar diameters.

Exposed to weather or earth.............. 5/8 in. (16 mm) Not exposed to weather or earth....... 1/2 in. (13 mm)

Table 3—Grout Space Requirements

Specified grout type

Maximum grout pour

height, ft (m)

Minimum grout a

space dimensions

for grouting cells of

hollow units

in. x in. (mm x mm)

Fine Fine Fine Fine

1 (0.3) 5 (1.5)

12 (3.7) 24 (7.3)

1 1/2 x 2 (38 x 51) 2 x 3 (51 x 76) b

21/2 x 3 (64 x 76) c 3 x 3 (76 x 76)

Coarse Coarse Coarse Coarse

1 (0.3) 5 (1.5)

12 (3.7) 24 (7.3)

11/2 x 3 (38 x 76) 21/2 x 3 (64 x 76)

3 x 3 (76 x 76) 3 x 4 (76 x 102)



When design requirements result in a large amount of closely spaced vertical steel reinforcement, or when reinforcement is required to be in place prior to installation of the masonry units, a variation of the vertical steel placement may be employed. The vertical bars can be secured in their proper position at the foundation or base of the wall before units are laid up. Instead of threading hollow units down over the vertical rods, open-ended units are typically used, enabling the mason to lay the block around the steel reinforcement as the wall is being erected. These units are manufactured with one or both end webs removed, resulting in an "A" or "H" shape, as illustrated in Figure 1.

Grout spaces must be clean prior to grouting. All reinforcing, bolts, other embedded items, and cleanout closures must be securely in place before grouting is started. The grouting operation should be continuously inspected.

Structural Design

Engineered reinforced concrete masonry is designed either by the allowable stress design method or by the strength design method. Engineered masonry, in which design loads are determined and masonry members are proportioned to resist those loads in accordance with engineering principles of mechanics, is most frequently analyzed by the allowable stress method. This method is considered a conservative approach to design; however, it does not predict material performance and behavior if masonry is stressed beyond allowable limits. The limit states design method evaluates member capacity (strength limit state) as well as member deformation under service loads (deformation limit state). Limit states design has particular advantages in providing for loads which are unpredictable, such as seismic loads or hurricane wind loads. Strength design of masonry is recognized by the Uniform Building Code (ref. 7).

Reinforced masonry design relies on reinforcement to resist tension, hence the tensile strength of masonry units, mortar and grout are neglected. By contrast, unreinforced masonry design considers the tensile strength of masonry in resisting design loads. The advantages of reinforced masonry include significantly higher flexural strength and ductility as well as greater reliability. Improved ductility of reinforced masonry is also a function of reinforcement, which continues to elongate well beyond the design level, allowing deformation beyond design levels without loss of strength. These deformations allow overloads to be redistributed to other members, thus improving structural performance when actual loads exceed design load levels.

Reliability of reinforced masonry is due to the predictable tensile strength of steel reinforcement and compressive strength of masonry, which results in a predictable strength of reinforced masonry elements.

Design Loads

Allowable stress design is based on service level loads, which are typical load levels occurring when the structure is in use, and members are proportioned using conservative allowable stresses (see Table 4). Strength design of masonry is based on a realistic evaluation of member strength subjected to factored loads which have a low probability of being exceeded during the life of the structure. Minimum design loads for allowable stress design (service loads) and for strength design (factored loads) are included in Minimum Design Loads for Buildings and Other Structures (ref. 3).

Allowable Stress Design

Allowable stress design principles and assumptions for reinforced concrete masonry are:

• Members are proportioned to satisfy applicable conditions of equilibrium and compatibility of strains within the range of allowable stresses when subjected to design service loads. • Strain in the reinforcement, masonry units, mortar, and grout is directly proportional to the distance from the neutral axis. Therefore, plane sections before bending remain plane after bending. • The tensile strength of masonry units, mortar and grout, is neglected. • Reinforced concrete masonry is a homogeneous, isotropic material. Reinforcement is perfectly bonded to masonry. • Stress is linearly proportional to strain within the working stress range.

Flexure

a Grout space dimension is the clear dimension between any masonry protrusion and shall be increased by the diameters of the horizontal bars within the cross section of the grout space. b UBC (ref. 7) requires 1 1/2 x 2 (38 x 51) c UBC (ref. 7) requires 1 3/4 x 3 (38 x 76)



Flexural compression and tension stresses are determined in accordance with accepted allowable stress design principles. This results in a triangular distribution of compressive stress from zero at the neutral axis to a maximum at the extreme compression fiber. Tensile stress in reinforcement is based on the strain in the steel multiplied by its modulus of elasticity. Strain in reinforcement increases linearly in proportion to the distance from the neutral axis to the centroid of reinforcement. Flexural members are proportioned such that the maximum calculated tensile and compressive stresses are within allowable stress limits. Increased flexural strength due to compression in reinforcement located on the compression side of the neutral axis is typically neglected unless it is confined by lateral ties to prevent buckling of the reinforcement.

Axial Compression

Axial loads acting though the neutral axis of a member are distributed over the net cross-sectional area of masonry. The compressive resistance of reinforcement is neglected unless the reinforcement is confined by lateral ties in accordance with the provisions for columns to prevent buckling of the reinforcement. Masonry members are proportioned such that the maximum axial compressive stress does not exceed the allowable axial compressive stress. The allowable axial compressive stress is based on the compressive strength of masonry, a slenderness coefficient, and an allowable stress coefficient.

Combined Axial Compression and Flexure

Most loading conditions result in a combination of axial load and flexure acting on the reinforced masonry member. Superimposing the stresses resulting from axial compression and flexural compression equals the combined stress. Members are proportioned such that the maximum combined stress does not exceed the allowable stress.

Shear

Shear acting on flexural members, shear walls, or reinforced masonry columns is resisted by the masonry or by reinforcement.

Where the masonry is designed to resist shear, the shear force is distributed over an area equal to the effective width of the member multiplied by the length of wall between the centroid of tension reinforcement and the location of the resultant compressive force.

The member is proportioned such that the maximum shear stress is limited to the allowable stress value or, alternatively, shear reinforcement is provided to resist the entire shear force. The required shear reinforcement is provided parallel to the direction of the shear force and distributed over a distance equal to the effective depth of the member. This reinforcement orientation provides shear resistance across a potential 45o diagonal tension crack in the masonry.

Strength Design

Strength design principles and assumptions for reinforced concrete masonry are:

• The strength of members is based on satisfying the applicable conditions of equilibrium and compatibility of strains when subjected to factored design loads. • Strain in the reinforcement, masonry units, mortar, and grout is directly proportional to the distance from the neutral axis. Therefore, plane sections before bending remain plane after bending. • The tensile strength of masonry units, mortar, and grout is neglected. • Reinforced concrete masonry is a homogeneous, isotropic material. Reinforcement is perfectly bonded to the masonry. • Masonry compressive stress distribution and masonry strain is assumed to be rectangular and uniformly distributed over an equivalent compression zone, bounded by the compression face of the masonry, with a depth of 0.85c (see Figure 3). • The maximum usable strain at the extreme compression fiber of the masonry is limited to 0.003.

Flexure

Research (ref. 6) has confirmed the accuracy of using the rectangular stress block model for calculating flexural strength of masonry. The required moment strength, Mu, is limited to the nominal moment strength, Mn = Asfy(d-a/2), multiplied by the strength reduction factor for flexure, = 0.8 (refs. 7, 8).

To ensure ductile behavior, the maximum reinforcement is limited to 50% of the reinforcement which produces balanced strain conditions, rbal (ref. 7). Balanced conditions occur when reinforcement reaches its specified yield strength at the same time that masonry reaches its maximum usable compressive strain of 0.003. This limit on reinforcement ensures the steel yields at strength level loads.



In addition to complying with flexural strength requirements, members should also be designed to have adequate stiffness to limit deflections or any deformations that may adversely affect strength or serviceability of a structure.

Axial Compression

Factored axial load is limited to the nominal strength of masonry multiplied by the strength reduction factor, = 0.65 (refs. 7,8).

Shear

The factored shear force is limited to the nominal shear strength multiplied by a strength reduction factor, = 0.80. This strength reduction factor is permitted to increase linearly to 0.85 as the required axial load strength, Pu, decreases from Pn to zero (ref. 8). The nominal shear strength is based on the shear strength of the masonry plus the strength of the shear reinforcement.

Table 4—Allowable Stressesa for Reinforced Concrete MasonryCompression Axial Fa = 1/4 f 'm[1-(h/140r)2], where h/r 99

Fa = 1/4 f ' m (70r/h)2, where h/r > 99

Flexural............................... Fb = 1/3 f ' m b Shear Where reinforcement is not provided to resist the entire shear: Flexural members....................... Fv = (f ' m)0.5, 50 psi max. (0.3 MPa) Shear walls M/Vd < 1.................. Fv = 1/3 [4-(M/Vd)](f ' m)0.5 [80-45(M/Vd)] psi max. M/Vd 1.................. Fv = (f ' m)0.5 35 psi max. (0.2 MPa) Where reinforcement is provided to resist all the calculated shear: Flexural members Fv = 3.0(f ' m)0.5, 150 psi max. (1.0 MPa) Shear walls M/Vd < 1.................... Fv = 1/2[4-(M/Vd)](f ' m)0.5 [120-45(M/Vd)] psi max. M/Vd 1........ Fv = 1.5(f ' m)0.5, 75 psi max. (0.5 MPa) Steel Reinforcement Tension Grade 40...................... Fs = 20,000 psi (138 MPa)

Grade 60...................... Fs = 24,000 psi (165 MPa)

Joint reinforcement..... Fs = 30,000 psi (207 MPa)

Compression...... Fs = 0.4 fy, 24,000 psi max (165 MPa)

a refs. 1, 2, 4, 7

b UBC (ref. 7) limits Fb to 2,000 psi (13.8 MPa) max.

Click below to open diagrams.Figures 1, 2 & 3

Table 5—Strength Design Criteria for Reinforced Concrete Masonry

Axial compression Pu A nf ' m [1-(h/140r)2] for h/r < 99

Pu A nf ' m [1-(70r/h)2] for h/r > 99

Shear Vu 6.0 (f ' m)0.5An + A fy for M/Vd 0.25



Notations

An net cross-sectional area of masonry, in.2 (mm2)

Av cross-sectional area of shear reinforcement, in.2 (mm2)

a depth of equivalent rectangular stress block, in. (mm) c distance from extreme compression fiber to neutral axis, in. (mm), a/0.85 d distance from extreme compression fiber to centroid of tension reinforcement, in. (mm) db nominal diameter of reinforcement, in. (mm) Es modulus of elasticity of steel, psi (MPa) Fa allowable compressive stress due to axial load only, psi (MPa) Fb allowable compressive stress due to flexure only, psi (MPa) Fs allowable tensile or compressive stress in reinforcement, psi (MPa) Fv allowable shear stress in masonry, psi (MPa) f 'm specified compressive strength of masonry, psi (MPa) fy specified yield stress of steel reinforcement, psi (MPa) h effective height of column, wall, or pilaster, in. (mm) M maximum moment occurring simultaneously with design shear force, V, at section under consideration, in.-lb (N.m) Mn nominal moment strength of a cross section before application of strength reduction factors, in.-lb (N.m) Mu required moment strength at a cross section to resist factored loads, in.-lb (N.m)

Pn nominal axial load strength, lb (N)

Pu factored axial load, lb (N) r radius of gyration, in. (mm) V design shear force, lb (N) Vu factored shear, lb (N) e strain

strength reduction factor p ratio of reinforcement area to gross masonry area, As/bd pbal reinforcement ratio producing balanced strain conditions

References

1. BOCA National Building Code. Country Club Hills, IL: Building Officials and Code Administrators International, Inc. (BOCA), 1993.

2. Building Code Requirements for Masonry Structures, ACI 530-92/ASCE 5-92/TMS 402-92. Reported by the Masonry Standards Joint Committee, 1992.

3. Minimum Design Loads for Buildings and Other Structures, ASCE 7-93. American Society of Civil Engineers, 1993.

4. Standard Building Code. Birmingham, AL: Southern Building Code Congress International, Inc. (SBCCI), 1994.

5. Standard Specification for Mortar for Unit Masonry, ASTM C 270-92a. American Society for Testing and Materials, 1992.

6. TCCMAR Research Program (Technical Coordinating Committee for Masonry Research).

7. Uniform Building Code. Whittier, CA: International Conference of Building Officials (ICBO), 1994.

Vu 4.0 (f ' m)0.5An + A fy for M/Vd 1.0

Interpolate values between M/Vd = 0.25 and 1.0

Flexure Mu As fy (d-a/2)

p 0.5 rbal



8. 1994 NEHRP Recommended Provisions For the Development of Seismic Regulations For New Buildings. Building Seismic Safety Council, 1994.



ALLOWABLE STRESS DESIGN OFCONCRETE MASONRY FOUNDATION WALLS

NCMA TEK

TEK 15-1BStructural (2001)

National Concrete Masonry Associationan information series from the national authority on concrete masonry technology

INTRODUCTION

Basements provide: economical living, working andstorage areas; convenient spaces for mechanical equipment;safe havens during tornadoes and other violent storms; andeasy access to plumbing and ductwork. Concrete masonry iswell suited to basement and foundation wall construction dueto its inherent durability, compressive strength, economy,and resistance to fire, termites, and noise.

Traditionally, residential basement walls have been con-structed of plain (unreinforced) concrete masonry, oftendesigned empirically. Walls over 8 ft (2.4 m) high or withlarger soil loads are typically designed using reinforcedconcrete masonry or using design tables included in buildingcodes such as the International Building Code (ref. 4).

DESIGN LOADS

Soil imparts a lateral load on foundation walls. Fordesign, the load is traditionally assumed to increase linearlywith depth resulting in a triangular load distribution. Thislateral soil load is expressed as an equivalent fluid pressure,with units of pounds per square foot per foot of depth (kPa/m).The maximum force on the wall depends on the total wallheight, soil backfill height, wall support conditions, soil type,and the existence of any soil surcharges. For design, founda-tion walls are typically assumed to act as simple verticalbeams laterally supported at the top and bottom.

Foundation walls also provide support for the structureabove, transferring vertical loads to the footing. When foun-dations span vertically, this vertical compression counteractsflexural tension, increasing the wall's resistance to flexure. Inlow-rise construction, these vertical loads are typically smallin relation to the compressive strength of concrete masonry.Further, if the wall spans horizontally, vertical compressiondoes not offset the flexural tension. Vertical load effects arenot included in the tables and design example presented inthis TEK (references 2 and 3 include vertical load effects).

EMPIRICAL DESIGN

The empirical design method uses historical experience


Keywords: allowable stress design, basements, basementwalls, empirical design, flexural strength, lateral loads,reinforced concrete masonry, structural properties

to proportion and size masonry elements. Empirical design isoften used to design concrete masonry foundation walls dueto its simplicity and history of successful performance.

Table 1 lists the allowable backfill heights for 8, 10 and12-inch (203, 254 and 305 mm) concrete masonry foundationwalls. Table 1 may be used for foundation walls up to 8 feet(2.4 m) high under the following conditions (ref. 1):

(1) terrain surrounding the foundation wall is graded todrain surface water away from foundation walls,(2) backfill is drained to remove ground water away fromfoundation walls,(3) tops of foundation walls are laterally supported prior tobackfilling,(4) the length of foundation walls between perpendicularmasonry walls or pilasters is a maximum of 3 times thefoundation wall height,(5) the backfill is granular and soil conditions in the areaare non-expansive,(6) masonry is laid in running bond using Type M or Smortar, and(7) units meet the requirements of ASTM C 90 (ref. 6).

Where these conditions cannot be met, the wall must beengineered using either an allowable stress design (see fol-lowing section) or strength design procedure (see ref. 5).

Table 1—Empirical Foundation Wall Design (ref. 1)a

Wall Nominal wall Maximum depth ofconstruction thickness, in. (mm) unbalanced backfill b, ft (m)

Hollow unit 8 (203) 5(1.52)masonry 10 (254) 6(1.83)

12 (305) 7(2.13)

Solid unit 8 (203) 5(1.52)masonry 10 (254) 7(2.13)

12 (305) 7(2.13)

Fully grouted 8 (203) 7(2.13)masonry 10 (254) 8(2.44)

12 (305) 8(2.4)

a see notes above for conditionsb unbalanced backfill is the distance from the top of the

basement floor slab to the top of the backfill

Table 2—Vertical Reinforcement for 8 in. (203 mm)Concrete Masonry Foundation Walls a, b

Wall Backfill Reinforcement size (No.) and spacing (in. o.c.) requiredheight, height, for equivalent fluid pressure of soil, psf/ft depth (kPa/m):ft (m) ft (m) 30 (4.71) c 45 (7.07) d 60 (9.43) e

7.3 (2.2) 4 (1.2) 5 @ 120 in. 6 @ 120 in. 5 @ 72 in.5 (1.5) 5 @ 72 in. 4 @ 40 in. 5 @ 40 in.6 (1.8) 4 @ 40 in. 5 @ 40 in. 6 @ 40 in.7 (2.1) 5 @ 40 in. 6 @ 40 in. 8 @ 48 in.

8 (2.4) 4 (1.2) 5 @ 120 in. 5 @ 96 in. 7 @ 120 in. h

5 (1.5) 5 @ 72 in. or 4 @ 32 in. or 5 @ 40 in. or 6 @ 120 in. h 8 @ 120 in. h 7 @ 72 in. h

6 (1.8) 4 @ 32 in. or 5 @ 32 in. or 5 @ 24 in. or 6 @ 72 in. h or 6 @ 48 in. or 6 @ 40 in. or 7 @ 96 in. h 7 @ 72 in. h 8 @ 56 in. h

7 (2.1) 5 @ 40 in. or 5 @ 24 in. or 6 @ 24 in. or 6 @ 56 in. h or 6 @ 32 in. or 7 @ 32 in. or 7 @ 72 in. h 8 @ 56 in. h 8 @ 48 in.

8 (2.4) 5 @ 24 in. or 6 @24 in. or 5 @ 8 in. 7 @ 64 in. h 8 @ 48 in.

9.3(2.8) 4 (1.2) 4 @ 96 in. or 5 @ 96 in. or 5 @ 72 in. or 5 @ 120 in. 6 @ 120 in. 7 @ 120 in. h



7 (2.1) 5 @ 32 in. or 5 @ 24 in. or 4 @ 8 in. or 8 @ 72 in. h 8 @ 56 in. h 7 @ 24 in.

8 (2.4) 6 @ 32 in. or 4 @ 8 in. or 7 @ 8 in. 8 @ 56 in. h 7 @ 24 in.

9 (2.7) 6 @ 24 in. or 6 @ 8 in. 8 @ 8 in. 8 @ 48 in.

10(3.1) 4 (1.2) 4 @ 72 in. or 5 @ 72 in. or 5 @ 64 in. or 5 @ 120 in. 6 @ 120 in. 7 @ 120 in. h



7 (2.1) 5 @ 32 in. or 6 @ 24 in. or 5 @ 8 in. or 8 @ 72 in. h 8 @ 48 in. 8 @ 24 in.

8 (2.4) 5 @ 24 in. or 5 @ 8 in. or 8 @ 8 in. 8 @ 56 in. h 8 @ 24 in.

9 (2.7) 6 @ 24 in. or 7 @ 8 in. ______ 8 @ 40 in.

WALL DESIGN

Tables 2 through 4 of this TEK have been rationallydesigned in accordance with the allowable stress design provi-sions of Building Code Requirements for Masonry Structures(ref. 1) and therefore meet the requirements of the InternationalBuilding Code even though the latter limits reinforcmentspacing to 72 in. (1829 mm) when using their tables. Additionalreinforcement alternatives may be appropriate and can beverified with an engineering analysis.

Tables 2, 3 and 4 list reinforcement options for 8, 10 and12-in. (203, 254 and 305-mm) thick walls, respectively. Theeffective depths of reinforcement, d, (see Table notes) used arepractical values, taking into account variations in face shellthickness, a range of bar sizes, minimum required grout cover,and construction tolerances for placing the reinforcing bars.

Tables 2 through 4 are based on the following:(1) no surcharges on the soil adjacent to the wall and no

hydrostatic pressure,(2) negligible axial loads on the wall,(3) wall is simply supported at top and bottom,(4) wall is grouted only at reinforced cells,(5) section properties are based on minimum face shell

and web thicknesses in ASTM C 90 (ref. 6),(6) specified compressive strength of masonry, f '

m , is

1,500 psi (10.3 MPa),(7) reinforcement yield strength, f

y, is 60,000 psi (414

MPa),(8) modulus of elasticity of masonry, E

m , is 1,350,000 psi

(9,308 MPa),(9) modulus of elasticity of steel, E

s , is 29,000,000 psi

(200,000 MPa),(10) maximum width of compression zone is six times the

wall thickness (where reinforcement spacing exceedsthis distance, the ability of the plain masonry outsidethe compression zone to distribute loads horizontallyto the reinforced section was verified assuming two-way plate action),

(11) allowable tensile stress in reinforcement, Fs, is 24,000

psi (165 MPa),(12) allowable compressive stress in masonry, F

b , is 1/3 f '

m

(500 psi, 3.4 MPa),(13) grout complies with ASTM C 476 (2,000 psi (14

MPa) if property spec is used) (ref. 7), and(14) masonry is laid in running bond using Type M or S

mortar and face shell mortar bedding.

DESIGN EXAMPLEWall: 12-inch (305 mm) thick,12 feet (3.7 m) high.

Loads: equivalent fluid pres-sure of soil is 45 pcf (7.07 kPa/m), 10 foot (3.1 m) backfillheight. No axial, seismic, orother loads.

Using Table 4, #8 bars at 40in. (M 25 at 1016 mm) o.c. aresufficient.

Notes to Tables 2, 3, and 4:a effective depth of reinforcement (distance from extreme compres-

sion fiber to centroid of tension reinforcement), d, is 4 5/8 in. (117mm) minimum

b metric equivalents: 1 in. (25.4 mm); No. 4 bar (M 13); No. 5 (M16); No. 6 (M 19); No. 7 (M 22); No. 8 (M 25)

c granular soil backfilld drained silty sand or clayey silt backfille clay soil (non-expansive) backfillf effective depth of reinforcement d, is 6 5/8 in. (168 mm) minimumg effective depth of reinforcement d, is 8 5/8 in. (219 mm) minimumh use Portland cement/lime or mortar cement mortar (Type M or S)

(7.07 kPa/m )45 psf/ft

12 ft

(3.

7 m

)

10 ft

(3.

1 m

)

Table 3—Vertical Reinforcement for 10 in. (254 mm)Concrete Masonry Foundation Walls b, f


7.3 (2.2) 4 (1.2) No reinforcement 5 @ 120 in. 5 @ 96 in.5 (1.5) 4 @ 72 in. or 5 @ 72 in. or 5 @ 64 in. or

5 @ 120 in. 6 @ 120 in. h 7 @ 120 in. h



8 (2.4) 4 (1.2) No reinforcement 5 @ 120 in. 5 @ 96 in.5 (1.5) 5 @ 120 in. 5 @ 72 in. 5 @ 64 in.6 (1.8) 5 @ 72 in. or 5 @ 56 in. or 5 @ 40 in. or

6 @ 120 in. h 7 @ 96 in. h 7 @ 72 in. h

7 (2.1) 5 @ 56 in. or 5 @ 40 in. or 5 @ 24 in. or 6 @ 72 in. h or 6 @ 56 in. or 6 @ 40 in. or 7 @ 96 in. h 7 @ 72 in. h 7 @ 56 in.


9.3(2.8) 4(1.2) No reinforcement 5 @ 120 in. 5 @ 96 in.5 (1.5) 4 @ 72 in. or 5 @ 72 in. or 5 @ 56 in. or

5 @ 120 in. 7 @ 120 in. h 8 @ 120 in. h





10(3.1) 4 (1.2) No reinforcement 5 @ 120 in. 5 @ 96 in.5 (1.5) 5 @ 96 in. 5 @ 72 in. 5 @ 56 in.6 (1.8) 5 @ 72 in. or 5 @ 48 in. or 5 @ 32 in. or

7 @ 120 in. h 8 @ 96 in. h 8 @ 72 in. h



9 (2.7) 5 @ 24 in. or 6 @ 24 in. or 4 @ 8 in. 7 @ 56 in. 8 @ 48 in.

10(3.1) 6 @ 32 in. or 4 @ 8 in. or 6 @ 8 in. 8 @ 56 in. 8 @ 32 in.

12(3.7) 4 (1.2) No reinforcement 5 @ 120 in. 5 @ 96 in.5 (1.5) 5 @ 96 in. 5 @ 72 in. 5 @ 48 in.6 (1.8) 5 @ 64 in. or 5 @ 40 in. or 5 @ 32 in. or

7 @ 120 in. h 8 @ 96 in. 8 @ 72 in. h



9 (2.7) 5 @ 24 in. or 4 @ 8 in. or 5 @ 8 in. 8 @ 56 in. 8 @ 40 in.

10(3.1) 8 @ 48 in. 5 @ 8 in. 8 @ 8 in.11(3.4) 8 @ 40 in. 7 @ 8 in.

Table 4—Vertical Reinforcement for 12 in. (305 mm)Concrete Masonry Foundation Walls b, g


7.3 (2.2) 4 (1.2) No reinforcement No reinforcement 5 @ 120 in.5 (1.5) 5 @ 120 in. 5 @ 120 in. 5 @ 72 in.6 (1.8) 4 @ 72 in. or 5 @ 72 in. or 5 @ 56 in. or

5 @ 120 in. 7 @ 120 in. h 7 @ 96 in. h


8 (2.4) 4 (1.2) No reinforcement No reinforcement 5 @ 120 in.5 (1.5) 5 @ 120 in. 5 @ 96 in. 5 @ 72 in.6 (1.8) 5 @ 96 in. or 5 @ 72 in. or 5 @ 56 in. or

6 @ 120 in. 7 @ 120 in. h 7 @ 96 in. h



9.3(2.8) 4 (1.2) No reinforcement No reinforcement 5 @ 120 in.5 (1.5) 4 @ 96 in. or 5 @ 96 in. or 5 @ 72 in. or

5 @ 120 in. 6 @ 120 in. 7 @ 120 in. h

6 (1.8) 5 @ 96 in. or 5 @ 64 in. or 5 @ 48 in. or 6 @ 120 in. 7 @ 120 in. h 7 @ 96 in. h



9 (2.7) 5 @ 40 in. or 5 @ 24 in. or 4 @ 8 in. or 7 @ 72 in. 8 @ 64 in. 8 @ 48 in.


6 @ 120 in. 7 @ 120 in. h 8 @ 96 in. h






6 @ 120 in. 8 @ 120 in. h 8 @ 96 in. h




10 (3.1) 5 @ 24 in. or 4 @ 8 in. or 4 @ 8 in. 8 @ 64 in. 8 @ 40 in.

11 (3.4) 8 @ 48 in. 8 @ 32 in. 5 @ 8 in.12 (3.7) 8 @ 40 in. 5 @ 8 in. 7 @ 8 in.



CONSTRUCTION ISSUES

This section is not a complete construction guide, butrather discusses those issues directly related to structuraldesign assumptions. Figures 1 and 2 illustrate typical wallsupport conditions, drainage, and water protection.

Before backfilling, the floor diaphragm must be in placeor the wall must be properly braced to resist the soil load. Inaddition to the absence of additional dead or live loadsfollowing construction, the assumption that there are nosurcharges on the soil also means that heavy equipmentshould not be operated close to basement wall systems that arenot designed to carry the additional load. In addition, thebackfill materials should be placed and compacted in severallifts, taking care to prevent wall damage. Care should also betaken to prevent damaging the drainage, waterproofing, orexterior insulation systems, if present.

REFERENCES1. Building Code Requirements for Masonry Structures,

ACI 530-99/ASCE 5-99/TMS 402-99. Reported by theMasonry Standards Joint Committee, 1999.

2. Concrete Masonry Design Tables, TR 121. NationalConcrete Masonry Association, 2000.

3. Concrete Masonry Wall Design Software, CMS-12111.National Concrete Masonry Association, 1999.

4. International Building Code. International Code Council,2000.

5. Strength Design of Reinforced Concrete Masonry Foun-dation Walls, TEK 15-2A. National Concrete MasonryAssociation, 1997.

6. Standard Specification for Loadbearing Concrete Ma-sonry Units, ASTM C 90-01. American Society for Test-ing and Materials, 2001.

7. Standard Specification for Grout Masonry, ASTM C476-01. American Society for Testing and Materials, 2001.

Figure 2—Typical Top of Foundation Wall

Figure 1—Typical Base of Foundation Wall

Note: wet and impermeable soils may require additionalwaterproofing

Waterproof ordamproofmembrane

(sloped)Grade

Floordiaphragm

boltAnchor

Filter paper orgeosyntheticmaterialGravel or

or bituminousExpansion joint

Full mortar

waterproofing exterior face of walls1) two / inch (6.4 mm) thick coats of portland cement, or,

plaster plus two brush coats of bituminous

3) one heavy troweled-on coat of cold,

joint

joint

Drain

stone fill

fiber-reinforced asphaltic mastic.

waterproofing,or,

2) one / inch (6.4 mm) thick coat of portland cement

Recommended protective coatings for

14

14

• masonry wall laid in running bond,• sufficient wall height above the lintel to form a 45o triangle,• at least 8 in. (203 mm) of wall height above the apex of the

45o triangle,• minimum end bearing (4 in. (102 mm) typ) is maintained,• control joints are not located adjacent to the lintel, and• sufficient masonry on each side of the opening to resist

lateral thrust from the arching action. The designer shouldconsider two cases. First, there should be a sufficientshear area of the masonry to resist the horizontal thrust,and second, there must be enough masonry to resist thein-plane overturning moment on the masonry adjacent tothe opening. In unreinforced masonry, this means usingvertical loads to offset overturning. In reinforced ma-sonry, vertical steel can be used to resist overturning. Asan alternative, the lintel could be a discrete length of alarger continuous bond beam to provide adequate re-straint. For a series of wall openings, the designer shouldconsider the offsetting effect of thrust from adjacentopenings.



ALLOWABLE STRESS DESIGN OFCONCRETE MASONRY LINTELS

TEK 17-1BStructural (2001)

Keywords: allowable stress design, design examples, lintels,openings in walls

INTRODUCTION

Lintels and beams are horizontal structural members de-signed to carry loads above openings. Although lintels may beconstructed of concrete masonry units, precast or cast-in-placeconcrete, or structural steel, this TEK addresses reinforcedconcrete masonry lintels only. Concrete masonry lintels have theadvantages of easily maintaining the bond pattern, color, andsurface texture of the surrounding masonry and being placedwithout need for special lifting equipment.

Concrete masonry lintels are sometimes constructed as aportion of a continuous bond beam. This construction pro-vides several benefits: it is considered to be more advanta-geous in high seismic areas or areas where high winds may beexpected to occur; control of wall movement due to shrinkageor temperature differentials is more easily accomplished; andlintel deflection may be substantially reduced.

DESIGN LOADS

Vertical loads carried by lintels typically include: (1) dis-tributed loads from the dead weight of the lintel, the dead weightof the masonry above, and any floor and roof loads, dead andlive loads supported by the masonry; and (2) concentratedloads from floor beams, roof joists, or other beams framing intothe wall. Axial load carried by lintels is negligible.

Most of these loads can be separated into the four typesillustrated in Figure 1: uniform load acting over the effectivespan; triangular load with apex at mid-span acting over theeffective span; concentrated load; and uniform load actingover a portion of the effective span. The designer calculates theeffects of each individual load and then combines them usingsuperposition to determine the overall effect, typically byassuming the lintel is a simply supported beam.

Arching ActionFor some configurations, the masonry will distribute ap-

plied loads in such a manner that they do not act on the lintel.This is called arching action of masonry. Arching action can beassumed when the following conditions are met (see alsoFigure 2):

Figure 1—Typical Lintel Load Components

Uniform Load

Triangular Load

Concentrated Loads

Uniform load over portionof span

Lintel

Clear span

Effective span Effective span = clear span + effective depth of lintel, d, butneed not exceed distance between centers of support (for

simply supported)

Table 2—Lintel Weights, lb/ft (kN/m)a

Nominal lintel Nominal wall thickness, in. (mm) height, in. 8 (203) 10 (254) 12 (305)

(mm) LIGHTWEIGHT CMU8 (203) 51(0.75) 65 (0.95) 79 (1.2)16 (406) 103(1.5) 130 (1.9) 158 (2.3)24 (610) 154(2.3) 195 (2.9) 237 (3.5)

NORMAL WEIGHT CMU8 (203) 58(0.84) 73 (1.1) 88 (1.3)16 (406) 116(1.7) 146 (2.1) 176 (2.6)24 (610) 174(2.5) 219 (3.2) 264 (3.9)

a Face shell mortar bedding. Unit weights: grout = 140 pcf(2,242 kg/m3); lightweight masonry units = 100 pcf (1602kg/m3); normal weight units = 135 pcf (2,162 kg/m3).

Lintel LoadingThe loads supported by a lintel depend on whether arch-

ing action can occur or not. If arching occurs, only the selfweight of the lintel, the weight of the wall below the archedportion, and concentrated loads are considered. Otherwise, theself weight, the weight of the wall above the lintel, roof and floorloads, and concentrated loads are considered. Self weight isa uniform load based on lintel weight (see Table 2).

When arching occurs, the wall weight supported by thelintel is taken as the wall weight within the triangular area belowthe apex (see Table 3). This triangular load has a base equal to theeffective span length of the lintel and a height of half the effectivespan. Any superimposed roof and floor live and dead loads areneglected, since they are assumed to be distributed to themasonry on either side of the lintel. When arching is not present,the full weight of the wall section above the lintel is considered,as are superimposed loads.

Concentrated loads are assumed to be distributed asillustrated in Figure 3. The load is then resolved onto the lintel asa uniform load, with a magnitude determined by dividing theconcentrated load by this length. In most cases, this results in auniform load acting over a portion of the lintel span.

When a lintel or other beam supports unreinforced masonry,Building Code Requirements for Masonry Structures (ref. 1)limits lintel deflection to the clear lintel span divided by 600 or to0.3 in. (7.6 mm) to limit damage to the supported masonry.

Figure 2—Arching Action

Figure 3—Distribution of Concentrated LoadFor Running Bond Construction

DESIGN EXAMPLE

Design a lintel for a 12 in. (305 mm) normal weight concretemasonry wall laid in running bond with vertical reinforcementat 48 in. (1.2 m) o.c. The wall configuration is shown in Figure 4.

Check for Arching Action. Determine the height of ma-sonry required for arching action. Assuming the lintel has atleast 4 in. (102 mm) bearing on each end, the effective span is:L = 5.33 + 0.33 = 5.67 ft (1.7 m).

The height of masonry above the lintel necessary forarching to occur in the wall (from Figure 2) is h + 8 in. (203 mm)= L/2 + 8 in. = 3.5 ft (1.1 m).

Because there is 18.0 - 7.33 = 10.67 ft (3.3 m) of masonryabove the lintel, arching is assumed and the superimposeduniform load is neglected.

Design Loads. Because arching occurs, only the lintel andwall dead weights are considered. Lintel weight, from Table 2, for12 in. (305 mm) normal weight concrete masonry units assumingan 8 in. (203 mm) height is,

Dlintel

= 88 lb/ft (1.3 kN/m)For wall weight, only the triangular portion with a height

of 3.5 ft (1.1 m) is considered. From Table 3 wall dead load is,D

wall = 68 lb/ft2 (3.5 ft ) = 238 lb/ft (3.5 kN/m) at the apex.

Maximum moment and shear are deter-mined using simply supported beam relation-ships. The lintel dead weight is considered auniform load, so the moment and shear are,

Mlintel

= wL2/8 = (88)(5.7)2/8 = 357 ft-lb(0.48 kN-m)

Vlintel

= wL/2 = (88)(5.7)/2 = 251 lb (1.1 kN)For triangular wall load, moment and

shear are,M

wall = wL2/12 = (238)(5.7)2/12 = 644 ft-lb

(0.87 kN-m)V

wall = wL/4 = (238)(5.7)/4 = 339 lb (1.5 kN)

Since the maximum moments and shearsfor the two loading conditions occur in thesame locations on the lintel, the momentsand shears are superimposed by simpleaddition:

End bearing

h = Effective span

4 in. (102 mm)

Clear opening

45°

Superimposed wall load

Lintel

8 in. (203 mm) minimum

heightWall

2

Effective span (see Figure 1)

minimum (typ)

LintelClear span

Effective span

Beam

30°

4 x wall thickness + width of bearing area of beam

30°

(see Figure 1)

Table 3—Wall Weights a

Wall weights (lb/ft2) for wall thicknesses, in. (mm), of:Grouted Lightweight units Normal weight units

cells 4 (102) 6 (152) 8 (203) 10 (254) 12 (305) 4 (102) 6 (152) 8 (203) 10 (254) 12 (305)None 16 23 30 36 41 21 31 40 48 55

48 in. o.c. 19 29 38 46 54 24 36 48 58 6840 in. o.c. 20 30 39 48 57 25 38 49 60 7032 in. o.c. 21 32 42 52 61 26 39 52 63 7424 in. o.c. 23 35 46 57 67 28 42 55 69 8116 in. o.c. 26 40 54 67 80 31 48 63 79 94Full grout 37 57 78 98 119 42 64 87 110 133

a Assumes face shell mortar bedding. Unit weights: grout = 140 pcf (2,242 kg/m3); lightweight masonry units = 100 pcf (1602 kg/m3); normal weight units = 135 pcf (2,162 kg/m3). kN/m2 = lb/ft2 x 0.04788

Mmax

= 357 + 644 = 1,001 ft-lb = 12,012 in-lb (1.4 kN-m)V

max= 251 + 339 = 590 lb (2.6 kN)

Lintel Design. From Table 4, a 12 x 8 lintel with one No. 4(M 13) bar and 3 in. (76 mm) or less bottom cover has adequatestrength. In this example, shear was conservatively computedat the end of the lintel. However, Building Code Requirementsfor Masonry Structures (ref. 1) allows maximum shear to becalculated using a distance d/2 from the face of the support.

Figure 4—Wall Configuration for Design Example

Case 2, No Arching Action. Using the same example,recalculate assuming a 2 ft (0.6 m) height from the bottom of thelintel to the top of the wall. For ease of construction, the entire2 ft (0.6 m) would be grouted solid, producing a 24 in. (610 mm)deep lintel.

Since the height of masonry above the lintel is less than3.5 ft (1.1 m), arching cannot be assumed, and the superimposedload must be accounted for.D

lintel = 264 lb/ft (3.9 kN/m), from Table 2. Because the lintel is

24 in. (610 mm) deep, there is no additional dead load due tomasonry above the lintel.D

total = 264 lb/ft + 1,000 lb/ft = 1,264 lb/ft (18.4 kN/m)

Mmax

= wL2/8 = (1,264)(5.7)2/8 x 12 in./ft = 61,601 in.-lb (7.0 kN-m)V

max = wL/2 = (1,264)(5.7)/2 = 3,602 lb (16.0 kN)From Table 4, a 12 x 24 lintel with one No. 4 (M 13)

reinforcing bar and 3 in. (76 mm) or less bottom cover isadequate.

REFERENCES1. Building Code Requirements for Masonry Structures, ACI

530-99/ASCE 5-99/TMS 402-99. Reported by the MasonryStandards Joint Committee, 1999.

Table 4—Allowable Shear and Moment Capacities for Concrete Masonry Lintels (width x height)a

Bottom cover, in. (mm):No. 1.5 (38) 2 (51) 2.5 (64) 3 (76)

Steel of Vall

Mall

Vall

Mall

Vall

Mall

Vall

Mall

size bars lb in.-lb lb in.-lb lb in.-lb lb in.-lb 8 x 8 lintels

No. 4 1 1,730 20,460 1,580 17,650 1,440 14,990 1,290 12,510No. 5 1 1,710 23,170 1,560 19,890 1,420 16,810 1,270 13,930No. 6 1 1,690 25,220 1,550 21,550 1,400 18,120 1,250 14,930No. 4 2b 1,730 25,460 1,580 21,860 1,440 18,480 1,290 15,320No. 5 2b 1,710 28,140 1,560 24,030 1,420 20,190 1,270 16,620

10 x 8 lintelsNo. 4 1 2,190 23,810 2,000 20,570 1,810 17,500 1,630 14,620No. 5 1 2,160 27,170 1,980 23,360 1,790 19,780 1,600 16,430No. 6 1 2,140 29,760 1,950 25,480 1,770 21,470 1,580 17,720No. 4 2 2,190 29,990 2,000 25,790 1,810 21,840 1,630 18,140No. 5 2 2,160 33,430 1,980 28,600 1,790 24,080 1,600 19,870


= 1500 psi (10.3 MPa)

5 ft 4 in. (1.6 m)

Window

3 ft 4 in. (1.0 m)

4 ft (1.2 m)

mf12 in. (305 mm) CMU

18 ft (5.5 m)

1,000 lb/ft (14.6 kN/m) superimposed uniform load


Table 4—Allowable Shear and Moment Capacities for Concrete Masonry Lintels (width x height) (continued)a

Bottom cover, in. (mm), of:No. 1.5 (38) 2 (51) 2.5 (64) 3 (76)

Steel of Vall

Mall

Vall

Mall

Vall

Mall

Vall

Mall

size bars lb in.-lb lb in.-lb lb in.-lb lb in.-lb 8 x 16 lintelsNo. 4 1 4,090 61,110 3,950 58,820 3,800 56,540 3,650 54,250No. 5 1 4,070 92,550 3,930 89,050 3,780 85,560 3,630 80,860No. 6 1 4,060 109,740 3,910 103,210 3,760 96,830 3,610 90,600No. 4 2b 4,090 107,750 3,950 101,420 3,800 95,240 3,650 89,200No. 5 2b 4,070 123,960 3,930 116,510 3,780 109,240 3,630 102,150



8 x 24 lintelsNo. 4 1 6,460 97,900 6,310 95,590 6,160 93,280 6,010 90,980No. 5 1 6,440 148,990 6,290 145,440 6,140 141,900 5,990 138,360No. 6 1 6,420 207,830 6,270 202,840 6,120 197,860 5,980 192,880No. 4 2b 6,460 190,850 6,310 186,300 6,160 181,760 6,010 177,220No. 5 2b 6,440 264,990 6,290 255,050 6,140 245,260 5,990 235,600



a Grade 60 reinforcement. Metric equivalents: f'm = 1,500 psi (10.3 MPa); N = lb x 4.44822; N.m = in.-lb x 0.112985; No. 4 bar (M 13); No. 5

(M 16); No. 6 (M 19). Table values differ from TEK 17-1A due to change in Em (ref. 1).

b For 8 in. (204 mm) lintels with two bars, low lift grouting is recommended for adjacent jambs to ensure proper grout flow and consolidation.



DESIGN FOR DRY SINGLE-WYTHECONCRETE MASONRY WALLS

TEK 19-2AWater Penetration Resistance (2001)

Keywords: architectural, capillary suction, coatings, constructiondetails, flashing, moisture, single-wythe, tooling mortar joints, walldrainage, water resistance, water repellents, weep holes

INTRODUCTION

Single-wythe concrete masonry construction has becomea predominant method of construction with the increased useof integrally colored architectural concrete masonry units.Single-wythe walls are cost competitive with other systemsbecause they provide structural form as well as an attractivearchitectural facade. However, single-wythe concrete ma-sonry walls, as opposed to cavity and veneered walls, requirespecial attention regarding moisture penetration issues.

The major objective in designing dry concrete masonrywalls is to keep water from entering or penetrating the wall. Inaddition to precipitation, moisture can find its way into ma-sonry walls from a number of different sources. Dry concretemasonry walls are obtained when the design and constructionaddresses the movement of water into, through, and out of thewall. This includes detailing and protecting roofs, windows,joints, and other features to ensure water does not penetratethe wall.

SOURCE OF WATER IN WALLS

The following moisture sources need to be considered inthe design for dry concrete masonry walls.

Driving RainMoisture in liquid form can pass through concrete ma-

sonry units and mortar when driven by a significant force.However, these materials generally are too dense for water topass through quickly. If water enters the wall, it often can betraced to the masonry unit-mortar interface due to improperlyfilled joints or lack of bond between the unit and the mortar.Cracks caused by building movements, or gaps between ad-joining building segments (roofs, floors, windows, doors, etc.)and masonry walls are other common points of water entry.

Capillary SuctionUntreated masonry materials typically take on water

through capillary forces. The amount of water depends on the

capillary suction characteristics of the masonry and mortar.Integral water repellents greatly reduce the absorption charac-teristics of the units and mortar, but may not be able to preventall moisture migration if there is a significant head pressure –2 in. (51 mm) or more. Post-applied surface treatments reducethe capillary suction of masonry at the treated surface as wellbut have little effect on the interior of the units. This isdiscussed in more detail later.

Water VaporWater as vapor diffuses toward a lower vapor pressure.

This means it will move from the higher toward the lower relativehumidity regions assuming no pressure or temperature differ-ential. Vapor in air of the same humidity and pressure, but of

Figure 1— Moisture Sources

85°F (29°C) 50% R.H.*

73°F (23°C) 50% R.H.*

73°F (23°C) 50% R.H.*

increases

Vapor rises astemperature

Moist high R.H.* air(condenses on cooling)

penetrationAbsorption

Flashing

73°F (23°C) 10% R.H.*

* Relative humidity

Ground waterpenetration

73°F (23°C) 75% R.H.*

73°F (23°C) 50% R.H.*

Grade

Vapor flow

Solarheat

Rain

different temperatures, will move from the higher temperatureto the lower. As air is cooled, it becomes more saturated andwhen it reaches a temperature called the dew point, the watervapor will condense into liquid form. See Figure 1.

DESIGN CONSIDERATIONS

Physical Characteristics of the UnitsOpen textured concrete masonry units possessing large

voids (a function of density, compaction, and gradation) tendto be more permeable than closed textured units. The type ofaggregate and water content used in the production of themasonry unit also affect capillary suction and vapor diffusioncharacteristics. Units that lend to mortar joint tooling such asstandard units and scored block will form a more watertight wallthan split-face units which are a little more difficult to tool.Fluted units are the most difficult to tool and therefore, the mostsusceptible to leakage. Horizontal effects such as corbels andledges that hold water are also prone to be less water resistant.Units should be aged at least 21 days if possible beforeinstallation to reduce the chance of shrinkage cracks at themortar-unit interface.

Integral Water RepellentsThe use of integral water repellents in the manufacture of

concrete masonry units can greatly reduce the absorptioncharacteristics of the wall. When using integral water repel-lents in the units, the same manufacturer's water repellent formortar must be incorporated in the field for compatibility andsimilar reduced water capillary suction characteristics.

Integral water repellents make masonry materials hydro-phobic, thereby significantly decreasing their water absorp-tion and wicking characteristics. While these admixtures canlimit the amount of water that can pass through units andmortar, they have little impact on moisture entering throughrelatively large cracks and voids in the wall. Therefore, evenwith the incorporation of integral water repellents, properdetailing of control joints and quality workmanship to precludebeeholes and unfilled or inadequate mortar joints is still essen-tial. Another advantage of integral water repellents is that theynot only help to keep water out but also inhibit the migrationof water to the interior face of the wall by capillary suction. SeeTEK 19-1 (ref. 7) for more complete information on integral waterrepellents for concrete masonry walls.

Surface TreatmentsFor colored architectural masonry it is recommended that

a clear surface treatment be post-applied whether or not inte-gral water repellent admixtures are used. Most post-appliedcoatings and surface treatments are compatible with integralwater repellents although this should be verified with theproduct manufacturers before applying. When using standardunits for single-wythe walls, an application of portland cementplaster (stucco), paint, or opaque elastomeric coatings workswell. Coatings containing elastomerics have the advantage ofbeing able to bridge small gaps and cracks. More detailedinformation on surface treatments and water repellents isavailable in TEK 19-1 (ref. 7).

Wall DrainageProper detailing of masonry wall systems, to ensure good

performance, can not be over emphasized. Traditionally,through-wall flashing has been used to direct water away fromthe inside face of the wall and toward weep holes for drainage.Modern techniques usually do not extend the flashing throughthe inside faceshell of the wall, as shown in Figure 2, in orderto retain some shear and flexural resistance capabilities. Inreinforced walls, some shear is provided through dowelingaction of the reinforcement and by design the reinforcementtakes all the tension per the Building Code Requirements forMasonry Structures (ref. 1). Proper grouting effectively sealsthe vertical reinforcement penetrations of the flashing. Theabsence of reinforcement to provide doweling in plain masonrymay be more of a concern, but loads tend to be relatively lowin these applications. If structural adequacy is in doubt, a shortreinforcing bar through the flashing with cells grouted directlyabove and below the flashing can be provided as shown inFigure 2C.

A critical aspect of flashing is to insure that a buildup ofmortar droppings does not clog the cells or weep holes. Acavity filter consisting of washed pea stone or filter paper,immediately above the flashing, can be provided to facilitatedrainage as shown in Figure 2. This should be accompaniedby a means of intercepting or dispersing mortar droppings asan accumulation can be sufficient to completely fill and blocka cell at the bottom. Mortar nets at regular intervals or fillingthe cells with loose fill insulation, a few courses at a time as thewall is laid up, are effective in dispersing the droppings enoughto prevent clogging. An alternative is to leave out facing blockat regular intervals just above the flashing until the wall is builtto serve as cleanouts. The units left out can be mortared in later.See TEK 19-4A and TEK 19-5A (refs. 4 and 6) for an in-depthdiscussion and additional details regarding flashing.

In addition to conventional flashing systems, proprietaryflashing systems are available that direct the water away fromthe inside face of the wall to weep holes without compromisingthe bond at mortar joints in the faceshells. Specialty units thatfacilitate drainage are also available from some manufacturers.Solid grouted single-wythe walls, as are sometimes required,are not as susceptible to moisture penetration since voids andcavities where moisture can collect are absent. However, fullycured units and adequate crack control measures are especiallyimportant to minimize cracks. Some regions of the countryrecess the bottom of the wall about an inch below the floor levelto ensure drainage to the exterior. Veneer and cavity walls(sometimes referred to as drainage walls) of course provide themost moisture resistance.

Control Joints and Horizontal ReinforcementTo alleviate cracking due to thermal and shrinkage move-

ments of the building, control joints and/or horizontal rein-forcement should be located and detailed on the plans. Wallcracking provides an entry point for rainwater and moist air thatmay condense on the inside of the wall. Specification of aquality sealant for the control joints and proper installation isa must. TEK 10-1A and TEK 10-2B (refs. 2 and 3) provideadditional information on crack control strategies.

Mortar and Mortar JointsThe type of mortar and mortar joint also have a great impact

on the watertightness of a wall. A good rule of thumb is to selectthe lowest strength mortar required for structural and durabilityconsiderations. Lower strength mortars exhibit better work-ability and can yield a better weather resistant seal at the mortar/unit interface. Concave or V-shaped tooling of joints, when themortar is thumbprint hard, improves rain resistance by direct-ing water away from the surface of the wall and by compactingthe mortar against the masonry unit to seal the joint. This isespecially important when using integral water repellent admix-tures to avoid reduced bond strength and cracking at the headjoints due to the decreased affinity of the units for water. Raked,flush, struck, beaded, or extruded joints are not recommended

as they do not compact the mortar and/or create ledges thatintercept water running down the face of the wall. Head and bedjoints need to be the full thickness of the faceshells for optimumwatertightness. Head joints particularly are vulnerable toinadequate thickness (see Figure 4).

Vapor BarriersContinuous vapor barriers to reduce the passage of water

vapor into the wall generally are used only when insulation isplaced on the inside face of the wall. The relatively small

Figure 2—Flashing Details to Maintain Structural Continuity

Figure 3—Weather Resistant Types of Mortar JointsFigure 4—Head and Bed Joints the Full Thickness of the

Faceshells are Crucial for Dry Walls

f

Properly mortared

ft

head jointInadequate

head joint

Thickness no lessthan t

Typical detail at inside of faceshell

b) Unreinforced cell

of washed pea stone. Alt. — leave out every other reduced size facing unit on top of flahing to serve as cleanouts unitl the wall is completed.* Cavity filter is any material used in conjunction with mortar nets to prevent mortar droppings from cloggin the weeps, i.e. filter paper or 2 in. (51 mm)

a) Reinforced cell

off to fit (typ. a & c)and part of webs cut

Cavity filter*

o.c. partially open2 ft. 8 in. (813 mm)Weep holes @

(typ. b & c)

1 in. (25 mm)

joints"L-shaped" head

Architectural unitwith inside faceshell

Edge of flashing

Solid unit or

Cavity filter*

from joint

to support flashingfilled hollow unit

sealed by mortar

1 in.

e) One-piece flashing

d) Two-piece flashing

Bond beam, lintel orfoundation (typ.)

c) Optional unreinforced masonry

4 in. (102 mm) unit

Drip edge (typ.)

48 in. (1219 mm) o.c.#5 (#16) min. @

Mortar net*

(25 mm)

Flashing


> 8 in. (203 mm) wall4 in. (102 mm) unit for8 in. (203 mm) wall,3 in. (76 mm) unit for

Concave joint

(preferred)"V" joint


REFERENCES1. Building Code Requirements for Masonry Structures,

ACI 530-99/ASCE 5-99/TMS 402-99, reported by theMasonry Standards Joint Committee, 1999.

2. Concrete Masonry Handbook, Fifth Edition, PortlandCement Association, 1991.

3. Control Joints for Concrete Masonry Walls - Empiri-cal Method, TEK 10-2B, National Concrete MasonryAssociation, 2001.

4. Crack Control in Concrete Masonry Walls, TEK 10-1A,National Concrete Masonry Association, 2001.

5. Flashing Strategies for Concrete Masonry Walls, TEK19-4A, National Concrete Masonry Association, 2001..

6. Specification for Masonry Structures, ACI 530.1-99/ASCE 6-99/TMS 602-99, reported by the Masonry Stan-dards Joint Committee, 1999.

7. Flashing Details for Concrete Masonry Walls, TEK19-5A, National Concrete Masonry Association, 2000..

8. Water Repellents for Concrete Masonry Walls, TEK 19-1,National Concrete Masonry Association, 1995.

amount of moisture that does get through passes through thewall by diffusion, provided that a “breathable” surface treat-ment is placed on the exterior. Wall thickness and dew pointsare also determining factors regarding vapor barriers. Mate-rials most commonly used for vapor barriers are plastic film,asphalt-treated paper, and aluminum foil.

CleaningWalls incorporating integral water repellents should not

be cleaned with a high-pressure wash as it drives water intothe masonry. Acidic washes should not be used since theymay reduce the water repelling properties of treated masonry.Keeping the masonry wall clean, as the construction progresses,using a brush and water minimizes cleaning efforts after themortar has hardened. Consult the integral water repellentmanufacturer for detailed cleaning recommendations.

SPECIFICATIONS

Well-worded specifications are essential to ensure properconstruction of the design details. Items to address in additionto those previously mentioned in the contract documents are:1) Specify in the contract documents that all work be in

accordance with the Specification for Masonry Struc-tures (ref. 5).

2) Require a qualified mason by documentation of experi-ence with similar type projects.

3) Require mock-up panels to assure an understanding ofthe level of workmanship expected and to be referred to as

a standard of reference until the project is completed.4) Proper storage of all masonry materials (including sand)

at the job site to protect from contaminants such as dirt,rain, and snow.

5) The tops of unfinished walls shall be covered at the endof each working day. The cover should extend two feetdown both sides of the masonry and should be heldsecurely in place.



FLASHING DETAILS FORCONCRETE MASONRY WALLS


INTRODUCTION

At critical locations throughout a building, moisturewhich manages to penetrate a wall is collected and diverted tothe outside by means of flashing. The type and installation ofdetails may vary depending upon exposure conditions, open-ing types and locationsand wall types. This TEKis a collection of typicalflashing details that haveproven effective over thelong term and a wide geo-graphical range. Thereader is also encouragedto review the companionTEK 19-4A FlashingStrategies for ConcreteMasonry Walls (ref. 3)which addresses the ef-fect of moisture on ma-sonry, design consider-ations, flashing materials,construction practices,and maintenance of flash-ing.

CAVITY WALLS

For cavity walls, asillustrated in Figure 1, thecavity ranges from a mini-mum of 2 in. to a maximumof 4 ½ in. wide with a mini-mum of a 1" clear airspacefor a drainage way if insu-lation board is placed inthe cavity. Cavities widerthan 4 ½ in. are permittedonly if a detailed analysis

Keywords: cavity walls, construction details, flashing, mois-ture, single wythe walls, vents, weep holes

Figure 1—Flashing Cavity Walls at Foundations

is performed on the wall ties per the Building Code Require-ments of Masonry Structures (ref. 1) The 1 in. clear airspaceworks only if the mason takes precautions to insure that mortarwill not be bridging the airspace. Such precautions would bebeveling the mortar bed away from the cavity or drawing apiece of wood up the cavity to collect mortar droppings. If

(per local practice)Vapor retarder

o.c. partially open

foundation

head joints

Drip edge

Brick ledge or

collection deviceor other mortar

2 ft. 8 in. (813 mm)Weep holes @

Flashing

Cavity filter

Wall ties

2 in. (51 mm) min. to4 / in. (114 mm)1

2

flashing into mortar joint

self adheringflashing, or tuck

Sealant at top offlashing unless

max. cavity

1 in. (25 mm) min.clear airspace

insulation 16 x 96 in.Closed cell rigid

between wall ties(406 x 2,438 mm)

Figure 2—Flashing Cavity Walls at Bond Beam Locations

Figure 3—Flashing Cavity Walls at Sills

precautions are not taken, it is sug-gested that a wider airspace be uti-lized, i.e. 1½ to 2 in. Also when usingglazed masonry veneer, a 2 in. mini-mum airspace is recommended withair vents provided at the top andbottom of the wall because of theimpermeable nature of the unit. Pro-prietary insulated drainage boardsor mats are available that provide anunobstructed drainage path thateliminate the need for a clear air-space (ref. 4).

As shown in Figure 1, the flashingin a cavity wall at the intersection ofthe foundation should be sealed tothe exterior faceshell of the struc-tural wythe, project downward tothe foundation surface, outward tothe exterior face of the wall, andterminate with a sloped drip. Weepholes should be located a maximumof 32 in. (813 mm) apart. Flashing atlintels and sills (shown in Figures 2and 3, respectively) is very similar.Although not shown, vents can beinstalled in the vertical head jointsat the top of masonry walls to pro-vide natural convective air flowwithin the cavity to facilitate drying.Prefabricated flashing boots areshown in Figure 7.

SINGLE WYTHE WALLS

Flashings in single wythe walls,like cavity walls should be posi-tioned to direct water to the exterior.This is normally accomplished us-ing two narrower units to make upthe thickness of the wall and placingflashing between them as shown inFigure 4. Care should be exercisedto insure that surfaces supportingflashings are flat or are sloping tothe exterior. This can be accom-plished by using solid units, lintel orclosed bottom bond beam unitsturned upside down similar to Fig-ure 3 or by filling cells of hollowunits with gravel or grout.

Flashing of single wythe walls atlintels, foundations, and bond beamsis accomplished in the same manneras shown in Figure 4 and sills areshown in Figure 6. Through-wallflashing is used in many areas of thecountry as shown in Figure 5. How-

NOTE: Rake outvertical joints wheremasonry units buttup to window jambsand fill with sealant

4 / in. (114 mm)2 in. (51 mm) min. to

1 (per local practice)Vapor retarder

max. cavity2

or other mortarcollection device

Weep holes @2 ft. 8 in. (813 mm)

Steel shelf angle

o.c. partially open

Drip edge

head joints

1 in. (25 mm) min.clear airspace

Wall ties

Cavity filter

Flashing

mortar joint

flashing unlessSealant at top of

flashing, or tuckself adhering

flashing into

lintelReinforced CMU

(406 x 2,438 mm)between wall ties

Closed cell rigidinsulation 16 x 96 in.

Vapor retarder

4 / in. (114 mm) max. cavity2 in. (51 mm) min. to

clear airspace1 in. (25 mm) min.

21

(per local practice)

Wall ties

Drip edge

1 / in. (38 mm)21

concrete sill

Concrete masonry sill units or precast

Weep holes 24 in. (610 mm) o.c.

Min. slope 15 ° One piece flashing

lintel unitSolid CMU or inverted

Sealant

membrane

Window frame

Unit 2 in. (51 mm)thicker than units

1 in. (25 mm) min. clear airspace

above and below

min.

to support sill

between wall ties(406 x 2,438 mm) insulation 16 x 96 in.Closed cell rigid

NOTE TO PRINTER:THIS IS A FILLER PAGE

THAT IS NOT TO APPEAR INTHE FINAL DOCUMENT.DO NOT USE THIS PAGE

Figure 4—Flashing Single Wythe Walls

Figure 7—Prefabricated Flashing Boots Figure 8—Flashing Single Wythe

Figure 5—Single Wythe Through-Wall

Bond beam, lintelor foundation

termination angle

1 in. (25 mm) min.

Interior flashing

collection deviceother mortarCavity filter or

Insidecorner

Outsidecorner

Enddam

Drip edge

Bond beam

shaped head jointspartially open "L"(813 mm) o.c.holes @ 2 ft 8 in.1 in. (25 mm) weep

collection deviceother mortarCavity filter or


Hooked bar in wall

Bearing strip

Hooked bar grouted in

Topping if required

4 in. (102 mm) (solid or

Stop flashing at inside of

slab keyway

filled) to support flashing

faceshell (see TEK 19-2A)

Architectural CMU

Hollow unit (cut)

detail this sheet)(refer to isometric

open head joints

Weep holes @ 2 ft. 8 in.(813 mm) o.c. partially

membrane

Sealant

Cavity filter or other

One piece flashing

motar collection device

Figure 6—Flashing Single Wythe Walls at Sills

Figure 8a—Isometric of Flashing Around End of Joist (ref. 5)

NOTE: Rake out verticaljoints where masonry unitsbutt up to window jambsand fill with sealant

e Walls at Roof/Parapet Intersection (ref. 5)

l Flashing Walls without Interior Finishes

NOTE: The structural effect of through-wall flashing must be carefully evaluated.

o.c. partially openhead joints

Drip edge

2 ft 8 in. (813 mm)Weep holes @

Plastic flashing

min.

Min. slope 15 °

(610 mm) o.c.Weep holes 24 in.

sill units or precastConcrete masonry

concrete sill

1 / in. (38 mm)

Drip edge

21

Sealant

Window frame

support flashing

4 in. (102 mm) CMU(solid or filled) to

Flashing

Sealant

Solid or filled CMU

to support flashingor inverted lintel unit

8 in. (203 mm)CMU (cut)

flashingOne piece

Joist

Wood nailer with anchor bolts

Sloping sheet metal copingcap with cont. cleat each side

Attachment strip

Counter flashing

Parapet flashing

faceshell (see TEK 19-2A)Stop flashing at inside of

anchor boltsGrout cores solid at

Cant


Figure 10—Splicing Metal Flashing

ever, the bond-breaking effects of this type ofdetail need to be evaluated in regard to thestructural performance of the wall. Additionalinformation for flashing single-wythe walls, par-ticularly architectural concrete masonry walls,and means for providing a higher level of struc-tural continuity at flashings is contained in TEK19-2A (ref. 2). Flashing single wythe walls at theends of bar joists which utilize wall pockets forbearing is shown in Figure 8 and 8a.

FLASHINGS AT COPINGS AND CAPS

The type of flashing detail to use on low-sloped roofs will in part depend on the type ofroofing membrane being used. As with anyflashing detail, the materials used should result ina uniform and compatible design. For example,joining two materials with significantly differentcoefficients of thermal expansion (such as metalflashing and bitumen roofing membrane) cancause tearing and failure of the joint. Manyroofing membranes also shrink as they age and ifthis movement is not provided for, fracturing ofthe upper course of the masonry parapet canoccur. Counter flashing provides the solution tothese problems as shown in Figure 8. Counterflashing also facilitates the reroofing process byallowing easy removal and access to the flashingmembrane fasteners.

During placement of the final courses ofmasonry in parapets, and commencing with thesecond course below the coping/cap location, agrout stop should be placed over cores so thatgrout can be placed for the positioning of anchorbolts (Figure 8).

In coping installations it is imperative thatpenetrations of through-wall flashing be tightlysealed to prevent water infiltration. A full mortarbed is required to be placed on the through-wallflashing to allow proper positioning of copingunits. Full head joints are placed between thecoping units as well as properly spaced controljoints. The joints between the coping unitsshould then be raked and a joint sealant applied.

Coping units should be sized such thatoverhangs and a drip reveal occur on both sidesof the wall. Metal caps require wood plates foranchorage which are usually attached to the wallwith anchor bolts. The cap should be sloped toprevent water from draining onto the exposedsurface of the masonry and should extend at least4 in. over the face of the masonry and sealed onboth sides. Smooth face or uniform split faceCMU should be considered for use under the capto ensure a relatively tight fit between the ma-sonry and cap which might be hindered by un-even CMU units such as split-face or fluted units.

Figure 9—Flashing Walls with Interior Finishes Alternate

NOTE: The structural effect of through-wall flashing must be carefully evaluated.

Isolation jointConcrete slab

2 in. (51 mm) min.

Cavity filter

Flashing*

Vapor retarder

Interior Drywall

Furring

Weep holes @

head jointso.c. partially open

Grade

Drip edge

2 ft 8 in. (813 mm)

Metal Flashing 4 in. (102 mm)lap min.

gap in flashing / in. (64 mm)1

4 Fully adheremembrane

Membrane

Metal Flashing

Step 1 Step 2

Splice Cross Section


INTERIOR WALL TREATMENTS

Concrete masonry walls with an interior treatment mayalso utilize a through-wall flashing installation of flashings asshown in Figure 9. However, as also noted in the figure,through-wall flashings generally serve as a bond-breakerwhich reduces the structural capacity of a masonry wall. Thiseffect should be carefully evaluated before implementing thistype of detail particularly in high-wind and seismic areas.

As shown in Figure 9, the flashing should project throughthe wall and be carried up on the interior concrete masonrysurface. Furring strips installed to receive the plastic vaporretarder and the interior gypsum board will hold the flashingin position. This procedure permits any water that may pen-etrate to the interior surface of the concrete masonry wall todrain out at the base of the wall. Weep holes should projectcompletely through the wall thickness. Vents if used shouldproject into the core areas only.

SPLICING FLASHING

When splicing of the flashing is necessary, extra pre-cautions are required to ensure that these discreet loca-tions do not become sources of water penetration. Flashingshould be longitudinally continuous or terminated with anend dam as shown in Figure 7. The achievement of longi-tudinally continuous for plastic and rubber compoundflashing requires that the joints be overlapped sufficiently,

4 in. (102 mm) minimum, and bonded together with adhesiveif they're not self-adhering to prevent water movement throughthe lap area.

Lap splicing of metal flashing is not recommended as ithas a different coefficient of thermal expansion than that ofconcrete masonry. As the temperature fluctuates, the flashingmaterial will expand and contract differently that the masonrymaterial which can result in sealant failure and a potential pointof entry for moisture. A typical flashing splice is detailed inFigure 10. Here, the two sections of sheet metal type flashingthat are to be spliced are first installed with a ¼-in. gap betweenthem to allow for expansion of the flashing. Next, a section ofpliable self-adhering membrane (such as rubberized-asphalt)or other pliable membrane set in mastic is fully bonded to theflashing at the location of the gap.

REFERENCES

1. Building Code Requirements for Masonry Structures, ACI530-02/ASCE 5-02/TMS 402-02, reported by the MasonryStandards Joint Committee, 2002.

2.Design for Dry Single-Wythe Concrete Masonry Walls,TEK 19-2A, National Concrete Masonry Association, 2001.

3.Flashing Strategies for Concrete Masonry Walls, TEK19-4A, National Concrete Masonry Association, 2001.

4. Flashing...Tying the Loose Ends, Masonry AdvisoryCouncil, Chicago, IL, 1998

5. Generic Wall Design, Masonry Institute of Michigan, 1998.



FLASHING STRATEGIES FORCONCRETE MASONRY WALLS


Keywords: flashing, flashing materials, maintenance, mois-ture, vents, wall drainage, water resistance, weep holes

of masonry if the dew point temperature is reached. Duringcold weather, below 28 oF (-2 oC), water vapor can accumu-late on a cold surface and from frost or increase thequantity of ice within the masonry.

Although it is commonly thought that moisture prob-lems stem only from the external environment, this is notalways the case. For example, in some instances it ispossible for the humidity of interior air to cause waterdamage to the exterior of a structure. This damage mayappear in the form of water stains, ravelled mortar joints,spalled surfaces, or efflorescence.

DESIGN CONSIDERATIONS

Water MovementIn the design of any structure, the presence and movement

of water in any of its three forms needs to be considered.Significant forces that influence water movement include windpressure, gravity, and moisture absorption by the material.Dynamic wind pressure on the surface of an exposed wall candrive exterior moisture (in the form of rain or irrigation water)into the masonry. Gravity, which is always present, draws thefree water vertically downward, while the absorptive character-istics of the masonry can cause moisture migration in anydirection by capillary action.

It should also be recognized that these forces do not actindependently of one another. For example, wind-driven rainmay enter masonry through cracks at the interface betweenmortar and units and migrate downward through the wall dueto the force of gravity, or it may be transferred horizontallythrough the wall either by pressure or by flowing across thewebs of the units or mortar bridges. Wind-driven rain can alsobe absorbed by masonry units and carried from the exteriorsurface to the interior surface by capillary action. Additionally,ground water may be drawn upward by the wicking action of unitsplaced on porous foundations or by contact with moist soil.

Designers should never assume that any material is ca-pable of rendering a wall totally impervious to water penetra-tion. Surface treatments, designed to reduce the quantity ofwater entering a masonry structure, are helpful in this regard

INTRODUCTION

The primary role of flashing is to intercept the flow ofmoisture through masonry and direct it to the exterior of thestructure. Due to the abundant sources of moisture and thepotentially detrimental effects it can have, the choice of flash-ing material, and the design and construction of flashingdetails, can often be as key to the performance of a masonrystructure as that of the structural system.

The type of flashing material to be used is governed byboth environmental and design/build considerations. Envi-ronmental considerations include such factors as the physicalstate of moisture present (liquid, solid, or vapor), air movement,and temperature extremes as well as temperature differentials.Design/build considerations include the selection of the propertype of flashing material, location of the flashing, structural,and installation details. Drawings for flashing details, often theonly method of communicating the necessary informationbetween the designer and contractor, should be comprehen-sive and show sufficient detail for the proper interpretation andinstallation of flashing systems. A subsequent TEK 19-5AFlashing Details for Concrete Masonry Walls (ref. 3) willaddress drawing details.

Although flashings are the primary focus of this TEK, itshould be understood that the role of vapor retarders, airbarriers, and insulation are also important elements to considerfor any wall design as the performance of the entire system canbe dependent on the design of its individual components.

EFFECT OF MOISTURE ON MASONRY

The damage caused to a masonry structure (or its con-tents) due to the infiltration of moisture can take many forms,depending on the source and the physical state of the water.For example, in the liquid state, water penetrating to theinterior of a building may cause considerable damage to itscontents. In some extreme cases, water trapped within themasonry may freeze, inducing spalling and cracking of themasonry units or mortar. Alternatively, water vapor canlead to condensation inside the cores and on the surfaces

but should not be considered as a sole means of protection.Available as clear and opaque compounds, the effectivenessof surface treatments depends on their composition and com-patibility with the masonry. They also do not reduce themovement by capillary action (wicking) of any water that doespenetrate the masonry face through cracks or defects in themortar/masonry.

The use of integral water repellent admixtures in concretemasonry units and mortars can also reduce the amount of waterentering the masonry. In addition, they inhibit water penetratingthe masonry face from wicking to the back face of the wall.

Proper selection and application of surface treatments andintegral water repellents can greatly enhance the water resistantproperties of masonry, but they should not be considered assubsitutes for flashing. See TEKs 19-1 and 19-2A (refs. 8 and 2)for more information on water repellents for concrete masonry.

Flashing LocationThe proper design of masonry for resistance to water

penetration includes consideration of the various types of wallconstruction such as single wythe, cavity, veneer, etc. Duringthe design phase it should be understood that all exteriormasonry walls may be subjected to some degree of waterpenetration and/or water vapor movement during its designlife. Flashing is recommended for any location where thepotential exists for water penetration. Some of these criticallocations include at the top of walls and parapets, at allhorizontal obstructions such as over openings, beneath sills,above shelf angles, at the base of walls, and in walls at groundlevel to serve as a moisture retarder to reduce the amount ofwater wicked up into the masonry above grade.

When selecting the flashing material for a particular appli-cation, the service conditions, projected life of the structure,

and past performance characteristics of the flashing materialsshould be reviewed. Flashing should be designed to performsatisfactorily for the life of the building since repair or replace-ment can be very labor intensive and expensive.

FLASHING MATERIALS

A wide variety of flashing materials are available. Theselection of the type of flashing material to use can be influ-enced by several factors including cost, durability, compatibil-ity with other materials, ease of installation, aesthetic value,and performance. Table 1 summarizes some of the attributes forvarious flashing materials. The advantages and disadvan-tages of each must be weighed for each individual project toprovide the most cost-effective and desirable choice.

Prefabricated flashing boots may be available for insideand outside corners and end dams. These boots eliminate theneed for cutting, folding, or tucking the flashing materials atthese locations. However, due to construction tolerances,some of these prefabricated items, particularly those of rigidmaterials, may be difficult to fit into their intended location.

Sheet MetalsStainless steel is technically any of a large and complex

group of corrosion resistant iron chromium alloys possessingexcellent weather and chemical resisting properties. Preformedsections must be properly sized so that modification on the siteis minimal. Stainless steel flashing with a conventional an-nealed finish should comply with Standard Specification forStainless and Heat-Resisting Chromium-Nickel Steel Plate,Sheet, and Strip, ASTM A 167 (ref. 6). Generally, Type 304stainless steel with a minimum thickness of 0.010 in. (0.25 mm)is satisfactory. Lap sections require solder conforming to

Table 1—Flashing Material Properties (refs. 1 and 7)

Material Advantages Disadvantages

Stainless steel Very durable, non-staining Difficult to solder and form

Cold-rolled copper Flexible, durable, easily formed and joinedDamaged by excessive flexing, can stainsurfaces

Galvanized steel Easy to paint and durableDifficult to solder, corrodes early in acidic andsalty air

Lead-coated copper Flexible, durable, non-stainingDifficult to solder, damaged by excessiveflexing, metal drip edge suggested

Copper laminates Easy to form and joinDegrades in UV light, more easily torn thanmetal

EPDM Flexible, easy to form and join, non-stainingAesthetics if not used with a metal drip edge,full support recommended

Rubberized asphaltFully adhered, separate lap adhesive notneeded, self-healing, flexible, easy to form andjoin

Full support required, degrades in UV light,metal drip edge required

PVC Easy to form and join, non-staining, low cost Easily damaged, full support required, metaldrip edge required, questionable durability

Standard Specification for Solder Metal, ASTM B 32 (60% tinand 40% lead) (ref. 5). Stainless steel drip edges used incombination with other flashing materials offers economy anda drip edge that is maintainable.

Copper is a nonferrous metal possessing good ductilityand malleability characteristics. Like stainless steel, it alsopossesses excellent weather and chemical resistant properties.Preformed sections or sheet materials are easily modified toconform to site requirements. However, it should be cautionedthat once weathered, copper flashings produce a green patinathat may impart a green stain to adjacent masonry surfaceswhich some designers find objectionable.

Galvanized steel is less expensive than stainless steel butis subject to corrosive attack from salts and acids. Thegalvanized coating also may crack at bends, lowering thecorrosion resistance. As with stainless steel, it is also difficultto form and to solder laps effectively.

Composite FlashingsCombinations of metals and plastics are supplied by some

dealers. The composition and application of these combinedmaterials should be determined before use. Composites utiliz-ing copper are the most popular since they combine thedurability and malleability of copper with the nonstainingcharacteristics of a protective coating. Composites containingaluminum should be avoided.

Plastics and Rubber CompoundsPlastics are categorized as polymeric materials of large

molecular weight, usually polyvinyl chloride (PVC) or polyeth-ylene. Manufacturers of plastic flashings should be consultedfor documentation establishing the longevity of the plastic ina caustic environment (pH = 12.5 to 13.5), the composition ofthe plastic, ease of working at temperatures ranging from 20 to100 oF (-7 to 38 oC), and ability to withstand exposure toultraviolet light.

Ethylene Propylene Diene Monomer (EPDM) is a syn-thetic rubber that is used as a single ply roofing membrane aswell as flashing. It has better low temperature performance thanPVC and will not embrittle. It offers ultraviolet light and ozoneresistance and can be left exposed.

Self-adhering, rubberized asphalt membranes consist of acomposite of flexible plastic film for puncture and tear resis-tance combined with a rubberized asphalt adhesive layer. Thismaterial adheres to itself, requiring less effort to seal laps orcorners which speeds installation. It also self-adheres to thesubstrate which prevents water from migrating under theflashing and is self-healing in the event of punctures. However,it should not be applied to damp, dirty, or dusty surfaces andhas a typical lower limit installation temperature of 25 oF (-4 oC).Because itdegrades in the presence of extended UV exposure,it should not be left exposed and requires a metal drip edge.

CONSTRUCTION PRACTICES

To perform, flashing must be designed and installedproperly or it may aggravate rather than reduce water problems.Flashing should be longitudinally continuous or terminated

with an end dam. Longitudinally continuous requires thatjoints be overlapped sufficiently, 4 in. (102 mm) minimum, toprevent moisture from entering between the joints and theymust be bonded (joined) together with adhesive if they're notself adhering to prevent water movement through the lap area.With metal flashings a ¼ in. (6.4 mm) gap joined and sealed witha pliable membrane helps in accommodating expansion (ref.3).

Flashings should be secured at the top by embedment intothe masonry, a reglet, or should be adhesively attached so thatwater cannot infiltrate or move behind the attachment. Theflashing should then project downward along the outer surfaceof the inner wythe and then project outward at the masonry joint,shelf angle, or lintel where it is to discharge the water. Every effortshould be made to slope the flashing towards the exterior.Effectively placed mortar bed or sealant material can help promotethis drainage. The flashing should continue beyond the exteriorface of the masonry a minimum of ¼ in. (6.4 mm) and terminate witha sloped drip edge.

An additional design consideration for flashings includesensuring that all materials are compatible. For example, contactbetween dissimilar metals can result in the corrosion potential forone or both of the metals. Additionally, the coefficients of thermalexpansion for the flashing and masonry materials differ. Allflashing details should be designed to accommodate the result-ing differential movement.

Other recommended practices involve the use of tooledconcave mortar joints to reduce water penetration through themortar joints. Masons should be careful to ensure that mortardropped onto the flashing is minimized. This can be accom-plished by beveling the mortar in the faceshells adjacent to thecavities in cavity wall construction. In addition, cavity drain-age mats, gravel beds, screens, or trapezoidal drainage material(filter paper) are often used to prevent mortar droppings fromcollecting on the flashing which can form dams and block weepholes. Mortar collection devices at regular intervals or fillingthe cells with loose fill insulation a few courses at a time as thewall is laid-up, can be effective in dispersing minor mortardroppings enough to prevent clogging.

Weep holes, the inseparable companion to flashings,should provide free movement of water out of the concretemasonry cores, collar joints, or cavities. Any constructionpractice which allows forming the weep holes without inhibit-ing water flow may be used. Cotton sash cords and partiallyopen head joints are the most common types of weep holes.Cotton sash cords should be removed prior to putting the wallinto service to provide maximum unobstructed drainage. Ifnecessary, insects can be thwarted by inserting stainless steelwool into the openings or using plastic or metal vents.

VentsWeep holes often serve a dual function, first for water

drainage and second as vents. Vents are desirable in somemasonry wall systems to help reduce the moisture content ofthe masonry during drying periods. Air circulation through thecores and cavities within the masonry promotes equalization ofmoisture content throughout the masonry. Vents are consid-ered desirable where air is confined within masonry, such as inparapets or areas of high humidity such as natatoriums.



MAINTENANCE

Maintenance programs should involve preserving the“as-built” design documents, records pertaining to inspec-tions during the life of the structure, and continuing appraisalof the performance of the structure in addition to conventionalrepair and upkeep. Documentation of inspections, if efflores-cence and water stains are observed, and logs of reported waterpenetration and their identified location, assist in determiningproper corrective actions. Pictures with imprinted dates aresuggested.

Knowledge of the wall design and construction can influ-ence repair decisions. If flashing and weep holes were omittedduring construction, it may prove effective to simply drill weepholes and vents to promote drainage and drying. Weep holesso drilled should be either at the intersection of the bed andhead joints or into the cores at the bottom of the wall. Ventsshould be drilled at the top of the wall or directly below bondbeams. See TEK 8-1A Maintenance of Concrete MasonryWalls (ref. 4) for more detailed information on maintenance ofconcrete masonry walls.

When considering maintenance options, it is important toensure that a masonry wall's moisture control measures are keptintact. Thus, applying sealant beads, pargings, or coatings toa wall should be carefully weighed. Weep holes and ventsshould be maintained in an open condition to allow evacuationof moisture.

SUMMARY

Flashings are essential at foundations, bond beams, aboveand below openings, at shelf angles and at copings. Weepholes and vents reduce the moisture content of masonry walls.Proper selection of flashing materials, proper detailing, andproper installation will help ensure satisfactory performance.

REFERENCES1. The Building Envelope: Solutions to Problems, Proceedings

from a national seminar series sponsored by SimpsonGumpertz & Heger Inc., 1993.

2. Design for Dry Single-Wythe Concrete Masonry Walls, TEK19-2A, National Concrete Masonry Association, 2001.

3. Flashing Details for Concrete Masonry Walls, TEK 19-5A,National Concrete Masonry Association, 2001.

4. Maintenance of Concrete Masonry Walls, TEK 8-1A,National Concrete Masonry Association, 1998.

5.Standard Specification for Solder Metal, ASTM B 32-00,American Society for Testing and Materials, 2000.

6.Standard Specification for Stainless and Heat-ResistingChromium-Nickel Steel Plate, Sheet, and Strip, ASTM A167-99, American Society for Testing and Materials,1999.

7.Through-Wall Flashing, Engineering and ResearchDigest No.654, Brick Industry Association.

8. Water Repellents for Concrete Masonry Walls, TEK 19-1,National Concrete Masonry Association, 1995.

masonry technical notes for design and construction

Documents