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7

AN OVERVIEW

OF WALL SURFACES

L E A R N I N G O B J E C T I V E S

By the end of this chapter you should know:

I ten types of exterior siding material

I six components of a typical wall assembly

I four common problems that crop up on any exterior wall system

1C H A P T E R


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8 Part I Exterior Cladding

I N T R O D U C T I O N In this chapter we are going to look at exterior wall surfaces, including several

types of cladding. Our discussions here are focused on weather-tightness. We think

of the exterior as a weather-tight skin for the building.

1.1 MATERIALS AND CHARACTERISTICSThere are many siding materials, including

I masonry products such as brick, stone, poured concrete, and concrete block

I poured concrete

I stucco (either over wood frame or masonry)

I synthetic stucco (EIFS, or Exterior Insulation and Finish Systems)

I wood products, including shingles and shakes, plank siding, plywood, OSB,

and hardboard

Imetal products, including steel and aluminum

I vinyl

I asphalt shingles

I slate and clay tiles

I fiber-cement

Ideal Wall Claddings The best wall systems are highly resistant to water, wind, mechanical damage,

and vermin entry. They are inexpensive, easy to install, and low maintenance, have

great cosmetic appeal, and provide good security. They also provide thermal insu-

lation and have a long life expectancy. Most sidings do only some of these things

well. There are no perfect siding materials.

Table 1.1 summarizes the characteristics of some common wall coverings.

1.2 WALL ASSEMBLIESBefore we look at individual sidings, lets briefly review typical wall assemblies

(Figure 1.1). These include

I structural membersstuds or masonry, for example

I interior finishesplaster or drywall, typically

I insulation and an air/vapor barrier (usually on the interior side of the

insulation)

I sheathingwood plank, plywood, OSB, fiberboard, gypsum board, cement

board, etc.

I building paper or housewrap

I siding

Structural Members Structural members include wood frame and masonry walls. These are designed

to carry the live and dead loads from floors and roofs. They are also designed to

carry the dead load of the siding and the live load of wind. We dont get to see

much of the wall structure during an inspection.


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Strength Structural

Weather-Tight (Resistance Properties

(Water, Snow, to Mechanical (Capable of Insulating Maintenan

Surface Type Wind) Damage) Carrying Loads) Cost Value Requireme

Brick Varies Good Yes High Poor Low, unless

Stone Brick is porous painted

Concrete

Stucco Good, but Fair No Medium Poor Low, unless

vulnerable EIFS is good painted

at joints

Wood Good Fair No Medium Poor Low, unless

Shingles painted or

and Shakes stained

Wood Siding Good Fair No Medium Poor High, unles

(Clapboard, unpainted

etc.) or unstaine

Vinyl Good Fair to poor No Low Poor Low

Metal Good Fair to poor No Low Poor (insulated Low

(Aluminum metal slightly

and Steel) better)

Asphalt Good Poor No Low Poor Low

Shingles

Slate, Clay Good Good No High Poor Low

Tiles

Fiber Cement Good Good No Medium Poor Low

Plywood Good, but Fair No Low Poor High

vulnerable

at joints

Hardboard Fair Fair No Low Poor Low to High

and OSB Joints/edges Needs reg

vulnerable painting o

May swell staining

unless

prefinishe

T A B L E 1.1 Characteristics of Various Wall Surfaces


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Interior Finishes Interior finishes are largely cosmetic and provide the base for the interior

decoration. They also help to separate the indoor environment from the outdoor

environment by restricting air movement through the wall.

Insulation and Air/Vapor Insulation and air/vapor barriers are more important in cold climates than inBarriers warm climates, although they are found in most areas. The insulation can be between

the studs in a wood frame wall, or it can be mounted on either side of the wallstructure behind exterior or interior finishes.

The amounts of insulation installed vary depending on the climate, the local build-

ing requirements, and the builders or homeowners commitment to energy conser-

vation and low energy costs. Again, we dont get to see much of the insulation or air/

vapor barrier. Many older homes have no insulation or air/vapor barrier in the walls.

Sheathing Sheathing has traditionally been provided on the exterior of wood frame

walls. It adds rigidity to the structure to help prevent racking. Many modern build-

ings do not rely on sheathing to prevent racking, since most interior finishes pro-

vide adequate rigidity. Sheathings provide a substrate for building paper and help

to reduce air movement through the wall assemblies. Many sheathings are vapor

permeable or have loose fit joints, so they wont trap moisture moving out through

the wall. Moisture is carried through walls by the air that leaks through and byvapor diffusion (no air movement needed). The air-transported moisture is the

more important of these two mechanisms.

Insulating Sheathing Some sheathings are rigid insulation board. Their primary function is to control

heat loss.

Building Paper or The functions ofbuilding paper (also called building felts or sheathing paper)Sheathing Paper include

I protecting the wall from water that gets past the siding

I helping to prevent wind blowing into the wall system, which would reduce

the effectiveness of the insulation


F I G U R E 1.1 Wall Assemblies

Structural members(studs in this case)

Insulation

Sheathing(e.g., plywood)

Vapor barrier(interior side ofinsulation in coolerclimates)

Interior finish(e.g., drywall)

Flashing

Sill gasket

Siding

Building paperor housewrap

Foun

datio

n


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I allowing vapor moving through the wall from indoors to escape to the

exterior (building paper must breathe)

Not Always Required Sheathing paper may not be required under hardboard, plywood, fiber-cement,

synthetic stucco, or metal siding where all joints are protected against wind and

water penetration. Some argue that there are very few systems that provide 100

percent protection, especially at joints, against wind and water penetration.

Those people maintain that sheathing paper should be provided in all cases: thesheathing paper provides a backup or second line of defense against moisture

penetration.

Housewrap Building paper is, in many areas, being largely replaced by housewraps.

These are typically spun polyolefin fabrics that are designed to protect against

water that gets through the siding and against wind blowing into the wall system.

Proponents of housewraps maintain that these are more effective than building

paper. Housewraps also need to be breathable so that vapor moving out through the

wall system wont be trapped and condense in the wall assembly.

Again, in most cases, we wont be able to see whether building paper or house-

wrap was used behind the siding.

Siding Connectors Many sidings, including wood, metal, vinyl, slate, asphalt, clay, and fiber-

cement, are usually held in place with nails. Siding is typically attached throughthe building paper and sheathing to structural members, such as studs. Most

sheathings are not strong enough to support the siding itself with conventional fas-

teners. There are exceptions to this.

Masonry Ties Masonry veneer sidings are held against walls with metal ties. These ties have

several different shapes and sizes.

Stucco Stucco is typically held in place with wire mesh that is nailed through building

paper and sheathing.

Support for Siding Some wall surface systems must rest on the building foundations and footings

because of their weight (Figure 1.2). These heavier systems include stone, con-

crete, concrete block, and brick. Lighter sidings are hung on the building frame.

11Chapter 1 An Overview of Wall Surfaces

F I G U R E 1.2 Support for Siding

Sheathing Sheathing

Buildingpaper

Brick ties arefor lateralsupport only

Wirelath

Joist JoistMasonryveneer

Foundation Foundation

Flashing

Dripscreed

Stucco

Heavy sidings (brick, stone,concrete) must be supportedon foundations and footings

Lighter sidingscan be supportedby the buildingframe


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1.3 GENERAL STRATEGYNow, lets look at some of the issues that apply to all types of wall surfaces. They

include

1. Water penetration

2. Too close to grade

3. Too close to roofs

4. Planters and gardens against the wall

5. Vines

6. Insulation problems

1.3.1 Water PenetrationMost serious wall problems are related to water in one way or another. Rainwater

may enter wall systems in several ways. It may be driven by wind or it may enter

by gravity or by capillary action.

Condensation Water may also be a problem in wall systems if warm, moist air movingthrough the wall (from indoors in cold weather and from outdoors in warm

weather) is cooled and deposits condensation inside the wall system (Figure 1.3).

Smaller amounts of condensation may also form if moisture moves into the walls

by vapor diffusion.

You should watch for water damage to wall systems, although in many cases

Concealed Damageyou wont be able to see it. If the siding is deteriorating, there is a good chance

IMPLICATIONS

CAUSES


F I G U R E 1.3 Condensation in Walls

Insulation Drywall

Cool air Cool air

OutsideOutside Inside Inside

Warm, moist air Warm, moist air

Condensation CondensationExteriorsheathing

Floor framing Floor framing

Cross section

Summer Winter

Siding, vapor barrier, andsheathing paper not shown


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Masonry Masonry should usually be at least 6 inches above grade. There are exceptions

because some bricks, for example, are designed for use at and below grade. Youll

be able to tell on older buildings whether the brick was designed for use below

grade by looking for damage. On new homes, its hard to know. You should

describe any new brick within 6 inches of grade as suspect, but allow for the pos-

sibility that it may be the correct type.

Other Sidings Most other sidings, including wood and wood-based products, stucco, fiber-

cement, metal, and vinyl, should be at least 8 inches above grade.

Siding materials too close to grade are typically the result of

I poor original construction and landscaping

I grade levels altered during landscaping or surface water control work

Its possible that the siding is too close to grade because the building is settling, but

there are bigger problems if this is the case.

Its easy to recognize the damage to the wall cladding materials. This may

include

I spalling (crumbling or flaking) and cracked brick and missing mortar

Iobstructed weep holes in masonry veneer

I rotted wood

I swollen, buckled, or cracking wood-based products

I peeling paint

I staining

I rusted fasteners

I rusted lath and drip screed on stucco

Weep Holes Covered In some cases, veneer walls with weep holes and flashings along the bottom

course suffer dramatically if the weep holes are below grade (Figure 1.5). Water

wont be able to drain out, air wont be able to get in, and moisture may seep from

the soil into the building through weep holes. Severe spalling can occur.The more serious and concealed implications are the damage to the wall and

floor structures behind the siding. This includes rot and insect damage at sheath-

ing, studs, sill plates, headers, and floor joists.

Damage to interior finishes and components is also possible. Sometimes

damage is not visible until it is serious. This may be the first indication that there

is a problem.

Check around the building perimeter for adequate clearance between siding

and grade. Can you see part of the foundation? Where the siding is below or too

close to grade, look first for damaged siding. If possible, probe to look for damage

to the structural members behind.

Note the areas where siding is too close to grade and check inside the building

for evidence of water leakage and damage. Try to find the top of the foundationwall. How far above grade is the top of the wall?

The Worst Case The foundation wall may be too short to allow the siding to end 6 to 8 inches

above grade. This is the more serious situation. We cant remove soil and create a

trench around the house because well have a chronic flooding problem as surface

water is funneled against the house. The foundation is ideally raised to solve the

problem, but this can be very disruptive and expensive.

A Better Case If the siding is too close to grade because the grade has been elevated to form

a garden, for example, the solution may be to restore grade level to its original

position. This is less disruptive and expensive.

STRATEGY

IMPLICATIONS

CAUSES



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Look for a 1- to 2-inch separation of siding and roofing materials. Where there

is little or no clearance, look and probe for deteriorated siding materials.

1.3.4 Planters or GardensGardens should not be built against houses such that earth is held against the siding

(Figure 1.7). A raised planter with three sides and the building acting as the fourth

STRATEGY


F I G U R E 1.6 Siding Too Close to Roof

Siding should have 1"(preferably 2") clearancefrom roof shingles toprevent water damage

Metal stepflashings

F I G U R E 1.7 Watch for Planters or Gardens Against Walls

Cross section

Basement

Backfill

Foundation wall

Spalling

Rot

Topsoil

Waterinfiltration

Floor framing

Wall framing

Brick veneerWateringand rainPlanter raises

soil level nextto house


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1.3.7 SummaryWater kills houses. Its a problem at roofs, at foundations, and on the exterior

cladding. If you think about nothing else as you inspect the outside of homes, think

about water getting into the building.

CHAPTER REVIEW QUESTIONSInstructions: Answer the following questions on a separate sheet of paper; then

check your results against the answers provided in Appendix E. If you have trou-

ble with a question, refer back to the chapter to review the relevant material.

1. List ten exterior wall surface materials that youll commonly find.

2. List six common components of an exterior wall assembly.

3. List three functions of building or sheathing paper.

4. Housewrap is used instead of ________.

5. What is used to secure brick veneer walls to wood frame houses?6. List six common problems that are found on all wall systems.

7. What are the implications of a foundation wall that is below the exterior

grade level?

8. What are the implications of burying weep holes on brick veneer walls?

KEY TERMS

19Chapter 1 An Overview of Wall Surfaces

cladding

wall assemblies

structural members

interior finishesinsulation

air/vapor barriers

sheathing

building paper

housewrapsiding

spalling

weep holes

veneer walls

plantersvines

external cladding

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