How retro-reinforcement is done

Brickwork techniquesBrickwork has the characteristics listed in Box 1.In such circumstances, the most obvious techniqueis shown in Figure 1 on page 2.

Where the wall is the external leaf of a cavitywall with only dead loads from masonry above,the slots can be quite extensive with littlestructural risk as the vertical load is modest and theties provide lateral restraint. However, sometemporary propping, packing or jacking may be

required in advance of the slot formation in caseswhere walls have locally subsided and haveopened up either horizontal or angled cracks,especially those around openings.

Blockwork techniquesBlockwork and some stonework commonly hasthe characteristics listed in Box 2.

Obviously, the ‘brickwork’ technique can beused, where feasible. However, it is commonly aseasy to determine the required slot frequency bystructural calculation and to slot the masonry as

Retro-installation of bed jointreinforcement in masonry

Bob de Vekey

BRE Construction Division

GBG 62

Bed joint reinforcement, added during construction, is an acceptedtechnique for making masonry (brick, block and stonework) walls tougher,stronger in flexure and tension, and less likely to crack. It is also used withthe masonry to generate lintels (beams) within walls. In its traditional formof either ‘hoop iron’ or mild steel with only limited corrosion protection(galvanising or bitumen) it has a finite life and is expensive to treat orremove. However, austenitic stainless steel (ASS) versions are very durableand are now used widely, particularly for crack control. For about a decade, the industry has been developing methods forinstalling bed joint reinforcement into existing walls, ie ‘retro-reinforcement’. This allows the product to be used for crack repair(stitching), repairing sagging lintels and flat arches, developing arches orcantilevers within a wall to span over patches of subsidence, increasing theflexural strength (out of plane) and shear resistance of walls to combatwind and seismic loading, and reconnecting cracked or parted buttresses.

good

bui

ldin

g gu

ide

Box 1 Characteristics of brickwork

● Most bricks are fairly strong hard materials.● They are normally in thin regular layers of no more

than 75 mm thickness with a 10 ±2 mm mortar jointbetween each layer.

● They are frequently, though not invariably, fairfacedand constitute the finish of the building.

● They are the strongest and most durable componentof the wall.

● In the external leaf of a cavity wall dead loads fromhigher levels of brickwork are the only significant load.

Retro-installation of bed jointreinforcement could be appliedto these shrinkage cracks andthe dropped flat arch

Box 2 Characteristics of blockwork

● The units vary from relatively soft, easily worked tofairly hard materials.

● Regular layers, if present, are commonly 215 mmthick with a 10–15 mm mortar joint.

● Walls built from rubble, partly coursed stonework,ashlar stonework, etc. may have either a very roughplane joint or no continuous horizontal joint at all.

● The walls may be fairfaced but commonly will berendered over, thus making it difficult to discern themortar joints.

required with no attempt to ensure bed joints are used. This can have the tripleadvantages of: (a) allowing larger diameter (and cross-sectional area) bars,(b) bonding together the unit materials, and (c) allowing diagonal reinforcement forcases where shear strength is an issue.

Materials, products and equipment

DurabilityIt is essential to use materials that will give reliable long-term performance underthe exposure conditions and that will not suffer any corrosion/deterioration processthat reduces the section of reinforcement or that leads to expansive decay over anacceptable lifetime. For most externally exposed masonry, the minimumrecommended specification is for grade 304 austenitic stainless steel (ASS), orequivalent, for metal-based reinforcement. In cases where chlorides are known tobe present, or are likely to be introduced due to marine exposure or splash-up fromsalted roadways, 316 ASS or equivalent is the better specification. Europeanequivalents to these specifications are listed in EN845-1 and EN845-3 (Table 1).

Fibre-reinforced plastic rods should be durable but accelerated durability testdata should be sought from the manufacturer for critical applications. Cement-based or resin-based grouts should normally be durable but manufacturers may beable to supply performance data showing accelerated durability/weathering testresults, any shrinkage or expansion behaviour and any sensitivity to chemicalagents that may be present.

Fire performanceMost walls have several roles including acting as fire barriers. This requirement isusually expressed as a period over which the wall will continue to carry out its otherfunctions while resisting a fire on one side and preventing spread of the fire. Theperiod is set to allow sufficient time for evacuation of occupants and varies with thesize of building, the numbers of people and their mobility/state of consciousness.Small domestic houses have a half-hour requirement and this can be met by mostsystems where protected by plaster or plasterboard finishes. All other types ofbuilding have a requirement of an hour or more and polymer resin-basedreinforcement and/or grout should only be specified if it has been shown to besuitable by test.

ReinforcementThis should be durable and have a profile that will bond well to a grout system. Thisis generally achieved by using austenitic stainless steel rod that has been deformedto produce ribs, eg ‘Rebar’ (Figure 2), or twisted or drawn to produce helicalflanges along the length (see Figure 7). Other alternatives are slotted or deformedplate, punched tube, wavy rods and ribbed composite bars made from fibre-reinforced plastics. One system uses a filter sock around a punched tube or ribbedbar to control delivery of the grout along the length and to prevent leakage andwastage of grout into voids. Deformed (wavy) wires and expanded metal productsare also used in some applications but they will have a relatively low effectivestiffness, which reduces their usefulness as beam reinforcement.

Typical quoted performance figures for steel and reinforced plastic are given inTable 1 and Table 2 gives the cross-sectional area of some typical products which isnecessary for beam design.

Grout systemsGenerally, metal reinforcement works most satisfactorily with cement-based groutsystems. These will usually comprise an hydraulic cement and a fine round-grainedsand with an optimised grading, plus optional additives to increase plasticity and/orbonding to minimise shrinkage and to waterproof the grout. Polyester orepoxy–sand grouts are also used in some circumstances but have a mismatch ofthermal and moisture movement characteristics and Young’s modulus with metalsthat makes them less effective. Polymer grouts may be preferred for fibre-

2

Figure 1 Typical sequence of bed jointretro-reinforcement (all operations on thesame joint) [Note: This technique is subjectto European Patent No EP0494099 whenused with corrosion-resistant materialcomprising a core of 2–6 mm diameter andexternally projecting fins or ridges]

A Select suitable joints on the basis of apractical or engineering requirement.

B Ensure that the brickwork between thetwo layers of reinforcement, which formsthe shear connection, is sound with noobvious slip planes such as damp-proofcourses or membranes.

C Repair any cracks in the shear area. D Cut a slot into selected bed joints to a

maximum depth of about one-third (33%)of the leaf thickness.

E Clean and wet the slot with water, orapply a primer, if a cement-based grout isspecified.

F Part-fill the slot with grout, ensuring thatthe grout is right to the back.

G Push lengths of durable, high bond,reinforcing rod into the grout such that itsurrounds the rod. [Note: (1) spacersmay be needed to ensure that the groutfully envelops finely ribbed cylindricalbars, (2) it is usual to specify either oneor two bars per joint.]

H Repoint the front of the slot withmatching mortar and pointing style.

Resin adhesive/filler

Grout

reinforced plastic rods because of the better match of mechanical performance andbonding compatibility. Table 3 gives some typical performance specifications forproprietary grout systems.

Temporary propping and jacking equipmentTypical builders ‘Acrow-style’ props with screw adjustment may be used.Alternatively, screw/hydraulic jacks that are of a similar capacity to those used forwork on vehicles but have rigid extension pieces may be suitable. Hammered-insteel plate shims or timber wedges may also be adequate in some cases. Guidanceon the assessment of loads above openings is given in Good Building Guide 10 andguidance on the placement of props is given in Good Building Guide 15.

Slot-cutting equipmentCutting slots in masonry is potentially a messy operation. Generally, eitherdiamond or carborundum abrasive rotary saws are used or tipped chain saws insofter mortar and unit materials. If the cutting is carried out dry then a dust extractsystem is a necessity to meet health and safety requirements for the operatives.Breathing masks and eye protection should be provided. Wet cutting reduces theamount of airborne dust but ideally requires a slurry removal device such as a wetvacuum cleaner. Normal site safety equipment, including protective headgear,gloves and protective footwear is also necessary.

3

Table 1 Structural performance of reinforcing materialsMaterial 0.2% Proof Ultimate Nominal BS5628 Young’s Shear

strength tensile strength tensile strength modulus modulus(N/mm2) (N/mm2) (N/mm2) (kN/mm2) (kN/mm2)

Stainless steel 525 700 460 200 80Epoxy-glassfibre -— 240 --— 8.5 -—

Table 2 Cross-sectional area of some typical barsReinforcement type (all steel Maximum Cross-sectional Mass Nominal ultimate unless otherwise stated) diameter area per metre tensile strength

(mm) (mm2) (kg/m) (N/mm2)

Ribbed bar (rebar) 4 12.6 0.1 460Ribbed bar (rebar) + epoxy-glass 5 19.6 0.156 240Ribbed bar (rebar) 6 28.3 0.225 460Ribbed bar (rebar) 8 50.3 0.399 460Ribbed bar (rebar) + epoxy-glass 10 78.5 0.624 240Ribbed bar (rebar) 12 113.1 0.899 460Ribbed bar (rebar) + epoxy-glass 15 176.7 1.405 240Solid core with helical flange* 4.5 5.85 0.047 1220Solid core with helical flange* 6 6.5 0.052 1215Solid core with helical flange* 8 9.2 0.073 1115Solid core with helical flange* 10 13.5 0.107 1010Solid core with helical flange† 5 6.25 0.047 1108Solid core with helical flange† 6 7.39 0.062 1061Solid core with helical flange† 7 8.52 0.072 1127Solid core with helical flange† 9 14.88 0.122 1103Wound helix of 2 mm plate 5 10 0.079 140Wound helix of 2 mm plate 7 14 0.111 1401 mm wall punched tube 8 22 0.1751 mm wall punched tube 10 28.2 0.2241.5 mm wall punched tube 15 63.6 0.506

* Manufacturer A.† Manufacturer B.

Figure 2 Proprietary spacer on rebar tocentre it in the grout bedPhoto courtesy of the industry

Grout placement systemsNormal hand tools, eg trowels, are inefficient for placing grouts because it isessential to fill or part-fill the slot right to the back before placing the first or onlyreinforcing rod. In addition, the reinforcement should be placed as rapidly aspossible after grouting to facilitate effective embedment and bonding. Pumpeddelivery systems are much more effective since the nozzle can be pushed right tothe back. In addition, temporary front barriers can be used to allow pressure fillingusing extended nozzles and to control the filled depth. The delivery devices rangefrom adapted mastic guns for small-scale work up to pumped or air-pressurisedtank, high flow-rate/line systems.

When cement-based grouts are used it is essential to wet out the slot thoroughlybefore grouting to minimise de-watering and stiffening of the grout. After theinitial part-fill of grout, the reinforcement should be pushed into the grout tooptimise the bond and interaction between grout and rod. If more than one rod isused the slot should be re-grouted before each bar is placed.

Brick repair grouts and injection devicesIn fairfaced work, where necessary, bricks, stones, blocks, etc. may be repaired in-situ. Special polymer-based grouts, which are colour-matched to the masonryunits, are used for this purpose. To optimise colour stability, pigments or evenfinely powdered matching units should be used as a colorant. Dyes are not lightstable and will change colour rapidly in service. Some of the resins listed in Table 3may also be suitable for this application.

Repointing and replasteringIn fairfaced work, the outer part of the slot should be left free of grout to allow acolour- and texture-matched pointing mortar to be applied. As a guide, foroptimum bonding and durability of the pointing, BRE recommends that the depthof the remaining slot be about twice the height of the slot. Additional depth will berequired for recessed styles of pointing but not for struck, weathered or buckethandle styles. Guidance on pointing techniques is given in Good Building Guide 4,Digest 359 and Good Repair Guide 24.

Plastered or rendered walls require an additional slot depth of only a fewmillimetres to act as a key. Plastering techniques are covered in Good BuildingGuide 7 and Good Repair Guide 18, rendering specifications are given in GoodBuilding Guide 18 and guidance on repair of rendering is the subject of GoodBuilding Guide 24.

4

Table 3 Some published properties of proprietary grouts Product Units Epoxy Epoxy Polyester Cement-based grout

resin 1 resin 2 resin 1 2 3 4 5

Shelf life in cool dry storage months 9 18 12+ 24 12Pot life @ 20 °C minutes 5 5–7 20–30 90–120 45–60 60–90Cure period to set 36 hrs 15–20 min 12 hrs 160 min ~60 minCure period to full strength days 7 7 1 28? 28 <1 14–28 28/84Installation temperature range °C 5–25 5–25 5–35 4–25 0–35Required minimum clearance mm 2 3Test temperature °C 20 18 20 20 20Tensile strength fully cured N/mm2 35 20 5.3 3.3 5.0Flexural strength fully cured N/mm2 30 1.4 12.5 12.0Compressive strength fully cured N/mm2 60 55 23 39.5 65 40 65 55/80Compressive strength @ 1 day N/mm2 23 20 23 20Compressive strength @ 7 days N/mm2 31.5 30 45 35Bond strength to metal bar/tie N/mm2 6–10 5–16Young’s modulus fully cured kN/mm2 28 26.5 28 13.5

Structural safety and design considerationsBefore commencing the repair specification, all loadbearing applications must beevaluated by a competent engineer who should fully understand the load and stressstate in the structure and why the cracks have developed.

This applies to all cases where beams are to be generated within walls, for civilengineering structures and for upgrading of shear and flexural performance. For allsuch cases, it is necessary to calculate the likely loads and to produce a safeinstallation procedure. Temporary supports may be advisable for heavily loadedsituations. This is particularly important where large loads from floors and trimmerbeams span onto masonry above openings. Thicker bonded walls can be reinforcedusing 30–50 mm deep slots that constitute only 15–25% of the wall thickness so thewalls can usually cope with continuous slots. Slender walls with limited loadcapacity may need to be slotted in safe lengths. Further sections of slot can be cutbetween the earlier sections after the grout has hardened. Continuity can begenerated by leaving the end section of bar ungrouted at either end of the 1st slotand lapping the reinforcement before grouting the 2nd slots.

It should be noted that the slots depths exceed those recommended in BS 5628rules on chasing but should be acceptable as they are only temporary and are filledwith high strength grouts. Temporary supports should not be removed until thegrout has reached its design strength.

It is not possible to cover structural design issues in detail in a Good BuildingGuide but the general aspects listed in Box 3 need to be dealt with. While much ofthis can be calculated by a competent structural engineer, some performance databy test is usually required to be supplied by the system manufacturer to enableoptimum performance advantage to be realised. Many manufacturers can supplysuch data in dedicated handbooks and guidance literature.

Examples of applications for retro-reinforcement

Applications requiring engineering design (see section above)Reinstatement of sagging lintels and archesIt is common to find that cavity walls will have a substantial lintel to supportfloor/roof loads on the inner leaf but in the lightly loaded external leaf, a flat orshallow arch will have been deemed adequate support for the brickwork above. Notinfrequently, such openings perform acceptably because the original timber frameand glass acts as a fortuitous lintel. Deterioration of the window frame or itsreplacement with a u-PVC unit can undermine the support and provoke a partialcollapse of the brickwork. Solid walls may also suffer from such problems usuallywhere flat arches have been used because they are sensitive to small movements ofthe buttressing masonry on both sides. In Figure 3, the outside corner of theprojecting bay has insufficient buttressing capacity; this has allowed the arch todrop while the adjacent curved arch is in perfect condition.

5

Box 3 Structural design issues requiring consideration

● The dead and potential live loads on themasonry

● The span of the beams● Whether there are adequate support

bearings for the beam at the chosenspan length (either in the form of soundmasonry or foundation provision)

● The additional extension lengths of thereinforcement either side of the repaired(eg beam) section that are necessary toensure there is adequate load dissipationand that the masonry does not simplycrack again at the edge of the repairedsection

● The area of steel, etc. required in thetension fibre

● Whether steel is required in thecompression fibre and its area

● The grout specification and itscontribution especially in thecompression fibre

● Either a conservative estimate or, ideally,a measurement of the shear capacity ofthe remaining masonry between thereinforced areas of deep beams.Possible techniques can be based on the‘shove test’ described in the RILEMrecommendations listed in Referencesand further reading on page 8.

Figure 3 Example of a part-fallen flat arch in English-bonded brickwork

The brickwork may be reinstated and reconsolidated by installing lengths ofremedial reinforcement in the joints just above the window together with a furtherlength, five or more brick courses above. This technique generates an in-situreinforced, deep masonry beam. Any sag of the masonry should be taken out beforethe operation commences by jacking between the ground or the sill and theoverhanging masonry. It is also necessary to fully repoint any cracks and areas ofmasonry with loosened or spalled mortar. This is especially important when theproblem has been caused by shrinkable masonry units.

Where real arches are failing, it is often necessary to put vertical ties up from thearch into the reinforced zone to complete the repair and some supplementary crack-stitching may also be required.

SubsidenceSubsidence is a common cause of cracking and deterioration of masonry. Remedialreinforcement, combined in most cases with new piles, can often provide a lowercost, and less invasive, solution than massive strip underpinning works. In this case,it is essential for some engineering assessment to be carried out to determine thereason for the cracking, the extent of the subsidence and what remedy is required.

The classic case is where a single foundation pile has slipped, or length of stripfoundation has failed. This removes support part-way along the length of the wallwith the result that a vertical crack, sometimes wider at the base, is generated in themasonry wall as illustrated by Figure 4. The crack will often stop at the dpc linesince the top of the masonry below the dpc may well be in compression. It willusually be located over the main subsided foundation.

This situation may be dealt with by generating a deep beam within the masonryby use of bed joint reinforcement in two bands as shown in Figure 5. The masonrybeam spans from sound foundations either side of the subsided area in much thesame way as a lintel. For wider spans or more heavily loaded situations it may benecessary to have more than one band of reinforcement in adjacent joints. It isobviously necessary to establish that the foundation at either side is indeed soundand also that it is adequate for the increased load. Additional short-bored pileslinked onto the existing foundation may be necessary in some cases. In cases wheresufficiently deep masonry footings are present the main beam may be formedbelow the dpc after jacking or repacking but some crack repair will anyway benecessary in the superstructure.

Particularly in cases of subsidence, it will also be necessary to repair the innerleaf which usually bears a greater load. This can obviously be carried out on theinside face but some installers have developed techniques to allow it to be carriedout from the outside to reduce disturbance to the occupants (Figures 6 and 7).

Another common problem is subsidence of the corner of a foundation. Figure 8shows a real case and Figure 9 is a diagram of typical behaviour where thesubsidence is shown at A. In this case, the cracks may widen going up the wall andtheir path (B) will usually be diagonal resulting from the downward and outwardrotation of the corner. They will often stop at the dpc line (F). In order to supportsuch walls it is necessary to develop a cantilever beam in each of the walls meetingat the corner. This can be achieved by installing tension reinforcement (D) near the

6

Figure 4 Subsidence of a piled foundationhas caused a horizontal crack at the dpcline and vertical crack of the supported wallabove due to flexural failure

Figure 5 Beam formed over subsidedfoundation comprising: A grouted-in compression reinforcement, B grouted-in tension reinforcement, C shear coupling formed by original

masonry,D dpc line, E crack, F resin repair of cracked unit, G resin repaired or repointed perpend. A

similar repair is suitable for fallen lintels

top of the cracked section and compression reinforcement (C) near the base. Theupper bands will also stitch the crack but additional shorter length stitches (E) maybe required between the main reinforcing bands in the shear zone of the cantileverbeam. The alternative repair option of installing a new pile at the corner tosufficient depth combined with retro-reinforced beams is probably preferable andshould always be considered.

Upgrading out-of-plane and shear performanceOutside the UK, a common requirement is to increase the resistance of walls toseismic loading. Seismic loads generate both in-plane (shear) stresses whichrequire the use of diagonal reinforcement and out-of-plane loads (flexural stresses)which can be partially resisted by horizontal, vertical or diagonal reinforcement.Installation is often facilitated because the continental practice is to render walls,reducing aesthetic objections.

In the UK, apart from nuclear facilities, the main application will be to increasethe robustness of parapet walls and boundary walls against both wind load andimpact loads from people or vehicles. For this purpose, horizontal reinforcementgiving catenary action may be sufficient for some applications.

Civil engineering/heritage applicationsThe retro-reinforcement technique offers a valuable method for: ● repairing masonry bridges and tunnels by re-stitching arch rings, ● repairing cracks, ● re-attaching spandrel panels, and ● strengthening bridge parapets and high parapets on heritage buildings, such as

cathedrals, against wind or impact loading.

In many of these cases, additional vertical reinforcement will also be required.These are specialised repairs, however, and should only be attempted by specialistcontractors working with a structural engineer.

Applications that can be based on simple rules and tabular guidesStitching tension cracks due to movementMasonry has a low tensile strength and is fairly prone to cracking, particularly atpoints of weakness such as openings. It is also vulnerable at changes betweendifferent heights and thicknesses of wall. Figure 10 shows a typical occurrence

7

Figure 8 Typical example of subsidence ata corner producing a diagonal taperedcrack

Figure 7 Close-up view of insertion ofhelical-flanged retro-reinforcementPhoto courtesy of the industry

Figure 6 Installing helical-flanged retro-reinforcementPhoto courtesy of the industry

Figure 9 Repair technique option for cracking resulting from corner subsidence

where cracking has occurred in the reducedwall section over an opening. This is mostlikely for shrinkable masonry materials, iethose made with concrete and calcium silicatebut can also occur in clay brickwork as a resultof thermal expansion/contraction.

The traditional repair consists of localdemolition and rebuilding or replacement ofany cracked units with new whole ones. Thedisadvantage is that it is difficult to match newmaterials perfectly with old ones so the repairis often obvious and ugly as shown byFigure 11. Additionally, the repair offers onlylimited restraint to continued cyclic movementand can often fail again.

The new option is to: ● retain the existing materials, ● install bed joint reinforcement to inhibit

future movement and further cracking, and ● resin repair fine cracks in units or mortar

beds and/or repoint widely cracked perpendjoints.

The reinforcement needs to run around 0.5 minto sound masonry either side of the crackposition to spread any tensile load and ensurethat further cracks do not appear. In theexample in Figure 10, it would be prudent toinstall continuous bands of reinforcement overall the windows and to 0.5 m either side.

Reattaching cracked buttressesA technique is given in Digest 329 usingremedial wall ties. Alternative techniques are: ● to fix surface-mounted straps and plaster

over them.● to slot the masonry on the two internal

corners and insert bed joint reinforcement(see Figure 12 E).

● to grout reinforcement into a hole in theouter wall and apply the bed joint re-inforcement technique in the partition wallfor a sound connection (see Figure 12 F).

References and further readingBRE Digest329 Installing wall ties in existing construction 359 Repairing brick and block masonry

Good Building Guides4 Repairing or rebuilding masonry chimneys7 Replacing failed plasterwork

10 Temporary support: assessing loads above openings in external walls

15 Providing temporary support during work on openings in external walls

18 Choosing external rendering24 Repairing external rendering

Good Repair Guides18 Replacing plasterwork24 Repointing external brickwork

British Standards BS EN 845: Specification for ancillary components for

masonryPart 1: 2003: Ties, tension straps, hangers and bracketsPart 3: 2003: Bed joint reinforcement of steel meshwork

BS 5628: Code of practice for use of masonryPart 1: 1992: Structural use of unreinforced masonryPart 2: 2000: Structural use of reinforced and prestressed masonryPart 3: 2001: Materials and components, design and workmanship

RILEMRILEM recommendations of tests for masonrymaterials and structures: MS.B.2 measurement of theshear strength index of bed joints, materials andstructures. V31, 210, pp 370–372. 1998.

8

Good Building Guides have beendeveloped to provide practitioners withconcise guidance on the principles andpracticalities for achieving good qualitybuilding. The guides are designed toencourage and improve mutualawareness of the roles of differenttrades and professions.

The guides draw on BRE siteexperience and research, and on otherreliable sources, to provide cleartechnical advice and solutions. Everyeffort is made to ensure that theguidance given is the most authoritativeat the date of issue.

The guides are part funded by theDepartment of Trade and Industry underthe Partners in Innovation scheme. Thisleaflet is published with theDepartment’s consent, but the viewsexpressed herein are those of BRE andare not necessarily accepted orendorsed by the Department.

BRE is committed to providingimpartial and authoritative informationon all aspects of the built environmentfor clients, designers, contractors,engineers, manufacturers, occupants,etc. We make every effort to ensurethe accuracy and quality of informationand guidance when it is first published.However, we can take no responsibilityfor the subsequent use of thisinformation, nor for any errors oromissions it may contain.

BRE is the UK’s leading centre ofexpertise on building and construction,and the prevention and control of fire.Contact BRE for information about itsservices, or for technical advice, at:BRE, Garston, Watford WD25 9XXTel: 01923 664000Fax: 01923 664098email: enquiries@bre.co.ukWebsite: www.bre.co.uk

Details of BRE publications are availablefrom:www.brebookshop.comorIHS Rapidoc (BRE Bookshop)Willoughby RoadBracknell RG12 8DWTel: 01344 404407Fax: 01344 714440email: brebookshop@ihsrapidoc.com

Published by BRE Bookshop Requests to copy any part of thispublication should be made to:BRE Bookshop, Building Research Establishment,Watford WD25 9XXTel: 01923 664761Fax: 01923 662477email: brebookshop@emap.com

© Copyright BRE 2004October 2004ISBN 1 86081 724 6

www.bre.co.uk

Figure 11 Stitching of unmatched bricks has beenused to repair a shrinkage crack

Figure 12 Reconnection of a partition wall to anouter wallA Masonry units B Mortar layer C Crack at junction D Slotted mortar joint E Repair using bed joint technique F Alternative repair G Repointing (or replastering)

Figure 10 Typical shrinkage crack (the brickwork issupported by a lintel)