Materials for Architects and Builders

MATERIALS FOR ARCHITECTS AND BUILDERS

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MATERIALS FORARCHITECTS AND BUILDERS

Fourth edition

ARTHUR LYONS

MA(Cantab) MSc(Warwick) PhD(Leicester) DipArchCons(Leicester) Hon LRSA FHEAFormer Head of Quality, Principal Lecturer and Teacher Fellow, School of Architecture,

Faculty of Art and Design, De Montfort University, Leicester, UK

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CONTENTS

About the author viiPreface to fourth edition viiiAcknowledgements ixInformation sources xAbbreviations xi

1 Bricks and brickwork 1Introduction 1Clay bricks 1Unfired clay bricks 17Reclaimed clay bricks 17Brickwork 18Calcium silicate bricks 29Concrete bricks 33References 35

2 Blocks and blockwork 37Introduction 37Concrete blocks 37Clay blocks 43Gypsum blocks 44Blockwork 46Beam and block flooring 50Landscape blockwork 52

References 52

3 Lime, cement and concrete 55Introduction 55Lime 55Cement 58Concrete 70Reinforced concrete 84Visual concrete 89Concrete components 97References 98

4 Timber and timber products 105Introduction 105Timber 106Timber products 136

Recycling timber 154References 155

5 Ferrous and non-ferrous metals 164Introduction 164Ferrous metals 164Ferrous alloys 180Coated steels 182Aluminium 185Copper 190Lead 197Zinc 200Titanium 205Process of metallic corrosion 206References 208

6 Bitumen and flat roofing materials 216Introduction 216Cold-deck, warm-deck and inverted roofs 216Reinforced bitumen membranes 217Mastic asphalt 221Single-ply roofing systems 223Liquid coatings 225Green roofs 226References 227

7 Glass 231Introduction 231Manufacture 232Non-sheet products 234Sheet products 236Intelligent glass facades 255Glass supporting systems 255Glazing checklist 261References 261

8 Ceramic materials 266Introduction 266Ceramic products 268References 275

v i C O N T E N T S

9 Stone and cast stone 278Introduction 278Types of stone 278Stonework 289Deterioration of stone 294Maintenance of stonework 295Cast stone 296References 297

10 Plastics 301Introduction 301Polymerisation 301Polymer types 303Additives 304Degradation of plastics 304Properties of plastics 304Plastics forming processes 306Plastics in construction 307Recycling of plastics 316References 317

11 Glass-fibre reinforced plastics,cement and gypsum 323Introduction 323Glass fibres 323Glass-fibre reinforced plastics 323Glass-fibre reinforced cement 327Glass-fibre reinforced gypsum 329References 331

12 Plaster and board materials 333Introduction 333Gypsum plaster 333Lime plaster 339Calcium silicate boards 339References 339

13 Insulation materials 342Introduction 342Thermal and sound insulation materials 342Inorganic insulation materials 343Organic insulation materials 347Aluminium foil 352Chlorofluorocarbons in foamed plastics 353References 353

14 Sealants, gaskets and adhesives 359Introduction 359

Sealants 359Gaskets 364Adhesives 366References 369

15 Paints, wood stains, varnishesand colour 373Introduction 373Colour 373Paints 379Special paints 380Natural wood finishes 382References 383

16 Energy-saving materials andcomponents 385Introduction 385Photovoltaics 385Solar collectors 388Solar air heating systems 389Light pipes 389Heat pump systems 390Groundwater cooling systems 391Wind catchers 391Wind turbine systems 391Water management systems 392Phase change systems 393References 393

17 Recycled and ecological materials 396Introduction 396Straw bales 396Cardboard 397Rammed-earth and cob construction 397Earth-sheltered buildings 399Clay products 400Recycled tyres 400Papercrete 401Sandbags 402References 402

18 Sustainability 404Introduction 404Zero carbon targets 404Specification of materials 408Recycling and deconstruction 409References 409

Index 413

ABOUT THE AUTHOR

Dr Arthur Lyons, author of texts on building materi-als, was formerly head of quality, principal lecturer andteacher fellow for building materials at the LeicesterSchool of Architecture, Faculty of Art and Design, DeMontfort University, Leicester, UK. He was educatedat Trinity Hall Cambridge,Warwick and Leicester Uni-versities in the fields of natural sciences and polymerscience, and has a postgraduate diploma in archi-tectural building conservation. He was a lecturer inbuilding materials within schools of architecture andsurveying for 35 years. In recognition of his ser-vices to architects and architecture, Arthur Lyons was

honoured with life membership of the Leicestershireand Rutland Society of Architects and he is a Fel-low of the Higher Education Academy. He retains hisactive interest in architecture through liaison with thelocal society of architects and the Leicester Schoolof Architecture of De Montfort University. In addi-tion to this text, Arthur Lyons has written chaptersin Metric HandbookPlanning and Design Data, 3rdedition, 2008, Architectural Press; ICE Manual ofConstructionMaterials, 2009, Institution of Civil Engi-neers andConstructionMaterials Reference Book, 2010,Butterworth-Heinemann.

PREFACE TO FOURTH EDITION

Materials for Architects and Builders is written as anintroductory text to inform students at undergradu-ate degree and national diploma level of the relevantvisual and physical properties of the widest range ofbuilding materials. The fourth edition has been sig-nificantly enhanced by the addition of more colourimages, illustrating the materials and, in many cases,their use in buildings of architectural merit. The textembraces the broad environmental issues with sectionson energy saving and recycledmaterials. An additionalchapter on sustainability reflects the current debate onclimate change and governmental action to reduce car-bon emissions and ameliorate global warming. Thereare eighteen chapters covering the wide range of mate-rials under standard headings. Each chapter describesthe manufacture, salient properties and typical uses ofthe various materials, with the aim of ensuring theirappropriate application within awareness of their eco-logical impact.

European Standards are taking over from the pre-vious British Standards, and for most key materials,the European Norms have now been published. Gen-erally, this has led to an increase inrelevant standards for building materisome cases, both the British and Euroare current and are therefore includedreferences.

New and rediscovered old materiare becoming well integrated into sing processes, are described, togetherproducts yet to receive general acc

materials no longer in use are generally disregarded,except where increased concern for environmentalissues has created renewed interest. The use of chem-ical terminology is kept to the minimum required tounderstand each subject area, and is only significantlyused within the context of the structure of plastics.Tabulated data is restricted to an informative levelappropriate to student use. An extensive bibliographyand listed sources of technical information are pro-vided at the end of each chapter to facilitate directreference where necessary.

The text is well illustrated with over 270 line draw-ings and colour photographs, showing the production,appearance and appropriate use of materials, but itis not intended to describe construction details asthese are illustrated in the standard texts on build-ing construction. Environmental concerns includingenergy-conscious design and the effects of fire areautomatically considered as part of the broader under-standing of the various materials.

The text is essential reading for honours and foun-dation degree, BTEC and advanced GNVQ students

g anroadtoate uthe number ofals. However, inpean Standardsin the text and

als, where theytandard build-with innovativeeptance. Other

of architecture, building, surveyinand those studying within the benvironment subjects, who wishprinciples relating to the approprition materials.d construction,range of built

understand these of construc-

Arthur LyonsJanuary 2010

ACKNOWLEDGEMENTS

I acknowledge the support of the Leicester School ofArchitecture, Faculty of Art and Design, De Mont-fort University, Leicester, and Professor Brian Ford,School of the Built Environment, University of Not-tingham. I wish to thank my wife, Susan, for herparticipation and support during the production ofthis work, and also my daughters Claire and Eliza-beth for their constant encouragement. I am indebtedto the numerous manufacturers of building materialsfor their trade literature and for permissions to repro-duce their published data and diagrams. I am gratefulto building owners, architectural practices and theirphotographers for the inclusion of the photographs;and to Her Majestys Stationery Office, the BuildingResearch Establishment, the British Standards Insti-tute and trade associations for the inclusion of theirmaterial.

I should like to thank the following organisationsfor giving permission to use illustratio

Aircrete Products Association (Fig. 2Company Ltd. (Fig. 5.10); Architec(Figs. 8.6, 8.9 and 8.10); British Cetion (Figs. 3.5, 3.9 and 3.23); BritisRating Council (Fig. 7.17); British Stute (Figs. 2.8 and 5.28). Permissionextracts from BS EN 771 Part 1: 2002001 is granted by BSI. British Staobtained in PDF or hardcopy formatonline shop: www.bsigroup.com/shoping BSI Customer Services for hardc+44 (0) 20 8996 9001; Email: cservices@Building Research Establishment (Fig9.18)photographs from GBG 58, Di10/01, reproduced by permission of BBrick Plc. (Figs. 1.22, 1.24 and 1.25)

Resources (Fig. 4.39); Copper Development Associa-tion (Figs. 5.235.25); Corus (Figs. 5.2, 5.45.6, 5.11,5.13 and 5.16); EH Smith (Fig. 8.8); Glass BlockTechnology (Fig. 7.5); Hanson Brick Ltd. (Fig. 1.5);Ibstock Brick Ltd. (Figs. 1.3, 1.9, 1.10, 1.12, 1.15,1.21 and 2.9); Imperial Chemical Industries Plc.(Fig. 15.4); James & Son Ltd. (Fig. 11.8); KME UKLtd. (Fig. 5.25); Lead Contractors Association (Figs.5.27 and 5.29); Lead Sheet Association (Fig. 5.26);Lignacite Ltd. (Fig. 2.7); Make Architects (Fig. 4.1);Marshalls Plc. (Fig. 2.14); Metal Cladding and Roof-ing Manufacturers Association (Fig. 5.15); MetraNon-ferrous Metals Ltd. and Rheinzinc (Fig. 5.31);Monodraught (Figs. 16.6 and 16.7); NCS Natu-ral Color Systemproperty of Scandinavian ColourInstitute AB, Stockholm 2009. References to NCS

in this publication are used with permission of theScandinavian Colour Institute AB (Fig. 15.3); Natural

ilkinagesPyroig. 6f D.com9.4

nd 5TRA

onc.6) a

for bsiblethatesens:.3); Angle Ring

tural Ceramicsment Associa-h Fenestrationtandards Insti-

to reproduce3 and BS 6915:ndards can bes from the BSIor by contact-

opies only: Tel:bsigroup.com;

s. 2.3, 4.15 andgest 476 and IPRE; Baggeridge; Construction

Stone Products Ltd. (Fig. 9.13); P7.6, 7.9, 7.11, 7.24 and 7.25)imby permission of Pilkington Plc;Ruberoid Building Products (FCompany Ltd. (Fig. 7.13); Smith oSolar Centurywww.solarcentury16.3); Stancliffe Stone (Figs. 9.3,Construction Institute (Figs. 5.7 aeration of Great Britain (Fig. 9.6);Ltd. (Figs. 4.15 and 4.20); Trent C1.23, 3.20, 3.21, 9.21, 11.5 and 11opment Association (Fig. 5.31).

The text uses the generic namesals and components wherever posfew cases, products are so specificnames are necessarily used. In thnames are italicised in the text.gton Plc. (Figs.are reproducedbel (Fig. 7.15);

.3); Securiglasserby (Fig. 11.2);

(Figs. 16.2 andand 9.8); Steel

.12); Stone Fed-DA Technologyrete Ltd. (Figs.nd Zinc Devel-

uilding materi-. However, in aregistered tradecases the trade

INFORMATION SOURCES

Specific information relating to thematerials describedin each chapter is given at the end of the appropriatesection; however, the following are sources of generalinformation relating to construction materials.

Building Regulations 2000 and 2006, includingcurrent amendments and approved documents

RIBA Office Library and Barbour Index Building Research Establishment (BRE) pub-

lications Trade association publications Trade exhibitions Trade literature Architecture and built environment journals British Board of Agrement certificates British Standards European Standards Eurocodes Institution of Civil EngineersManual of Con-

struction Materials, 2009

European Standards (EN) have been published fora wide range of materials. A full European Standard,known in the UK as BS EN, is mandatory and over-rules any conflicting previous British Standard whichmust be withdrawn. Prior to full pdraft European Standards are codedavailable for comment, but not implem

Information Paper IP 3/99 (1999) identifies the issuesrelating to the adoption in the UK of the structuralEurocodes.

The Building Research Establishment (BRE) pub-lishes informative and authoritative material on awide range of subjects relating to construction. Tradeassociations and manufacturers produce promotionalliterature and websites relating to their particular areaof interest within the building industry. Architec-ture and building journals give news of innovationsand illustrate their realisation in quality construction.Much literature has recently been presented, includ-ing from governmental organisations, in respect of theneed to reduce energy consumption within the builtenvironment sector to ameliorate the effects of globalwarming and climate change.

Information for this text has been obtained froma wide selection of sources to produce a studenttext with an overview of the production, nature andproperties of the diverse range of building materials.New individual products andmodifications to existingproducts frequently enter the market; some materialsbecome unavailable. Detailed information and partic-ularly current technical data relating to any specificproduct for specification purposes must therefore be

facturrentublication, thepr EN and areentation. BRE

obtained directly from the manuers and cross-checked against curegulations.rers or suppli-standards and

ABBREVIATIONS

General

AAC autoclaved aerated concreteABS acrylonitrile butadiene styreneAC aggressive chemical (environment)ACEC aggressive chemical environment for

concreteAPAO atactic poly -olenAPM additional protective measuresAPP atactic polypropyleneAR alkali-resistantASR alkalisilica reactionBER building emission rateBFRC British Fenestration RatinBRE Building Research EstablisBREEAM BRE environmental assess

methodBS British StandardCAD computer-aided designCCA chromated copper arsenatCFCs chlorouorocarbonsCG cellular glassCIGS copper indium gallium selCIS copper indium selenideCL cross-laminated (timber)CMYK cyan magenta yellow blackCOSHH control of substances haza

healthCPE chlorinated polyethyleneCPVC chlorinated polyvinyl chloCS calcium silicateCSA Canadian standards associCSM chlorosulphonated polyethDC design chemical (class)DC direct currentDD draft for developmentDER dwelling emission rate

DPC damp-proof courseDPM damp-proof membraneDR (CR) dezincication-resistantDRF durability of reaction to reDS design sulphate (class)DSA design stage assessmentDZR dezincication-resistantEN EuronormENV Euronorm pre-standardEP expanded perliteEPC energy performance certicateEPDM ethylene propylene diene monomerEPR ethylene propylene rubberEPS expanded polystyrene

ylene

olymamalloerncilstfucemgypsplast

ber

conc

bons

eck

ng Councilhmentment

e

enide

rdous to

ride

ationylene

ETFE ethylene tetrauorethEV exfoliated vermiculiteEVA ethylene vinyl acetateEVOH ethyl vinyl alcohol copFEF exible elastomeric foFPA exible polypropyleneFRP bre reinforced polymFSC forest stewardship couGGBS ground granulated blaGRC glass-bre reinforcedGRG glass-bre reinforcedGRP glass-bre reinforced

polyesterGS general structural (timHAC high alumina cementHACC high alumina cementHB hardboardHCFCs hydrochlorouorocarHD high densityHDPE high-density polythenHIP home information paHL hydraulic limeHLS hue lightness saturatioICB insulating corkboardcopolymer

er

y

rnace slagentumic or

)

rete

x i i A B B R E V I A T I O N S

ICF insulating concrete formworkIGU insulating glass unitLA low alkali (cement)LD low densityLDPE low-density polytheneLED light-emitting diodeLRV light reectance valueLVL laminated veneer lumberMAF movement accommodation factorMB mediumboardMDF medium density breboardMF melamine formaldehydeMMC modern methods of constructionMPa mega PascalMTCS Malaysian timber certication schemeMW mineral woolNA National Annex (British Standard)NAOBL National windspeed databaseNCS Natural Color System

NHL non-hydraulic limeODP ozone depletion potentialOPC ordinary Portland cementOSB oriented strand boardPAS publicly available specicationPBAC polystyrene-bead aggregate cementPC polycarbonatePCM phase change materialsPCR post-construction reviewPE polyethylenePEF polyethylene foamPEFC programme for the endorsement of

forest certicationPET polyethylene terephthalatePEX crosslinked polyethylenePF phenolic foam/phenol formaldehydePFA pulverised fuel ashPHA partially halogenated alkanePIB polyisobutylenePIR polyisocyanurate foamPMMA polymethyl methacrylatePP polypropylenepr EN draft EuronormPS polystyrenePTFE polytetrauroethylenePUR rigid polyurethane foamPV photovoltaicPVA polyvinyl acetatePVB polyvinyl butyralPVC polyvinyl chloride (plasticised)PVC-U polyvinyl chloride (unplasticised)PVC-UE extruded polyvinyl chloride

PVDF polyvinylidene uorideRBM reinforced bitumen membraneRGB red green blueSAP standard assessment procedureSB softboardSBEM simplied building energy modelSBS styrene butadiene styreneSCC self-compacting concreteSFI sustainable forest initiativeSg specic gravitySIP structural insulated panelSS special structural (timber)ST standard (concrete mix)SUDS sustainable urban drainage systemT tolerance (class)TER target emission rateTFS thin lm siliconTH temperate hardwoodTHF tetrahydro furanTMT thermally modied timberTPE thermoplastic elastomerTPO thermoplastic polyolenTRADA timber research and development

associationTRM total relative movementUF urea formaldehydeUHPC ultra high performance concreteUV ultra-violet (light)VET vinyl ethylene terpolymerVOC volatile organic compoundsWER window energy ratingWF wood breWPC wood plastic compositeWW wood woolXPS extruded polystyrene

Units

dB decibelGPa giga pascal (1GPa= 1000MPa)MPa mega pascal (1MPa= 1N/mm2)m micron (106 m)nm nanometre (109 m)

Chemical symbols

Al aluminiumAs arsenic

A B B R E V I A T I O N S x i i i

C carbonCa calciumCd cadmiumCl chlorineCr chromiumCu copperF uorineFe ironGa galliumIn indiumMn manganeseMo molybdenumN nitrogenNi nickelO oxygenS sulphur

Se seleniumSi siliconSn tinTe telluriumTi titaniumZn zinc

Cement notation

C2S dicalcium sicilateC3S tricalcium silicateC3A tricalcium aluminateC4AF tetracalciumaluminoferrite

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1BRICKS AND BRICKWORK

IntroductionOriginally, bricks were hand-moulded frommoist clayand then sun-baked, as is still the practice in certainarid climates. The ring of clay bricks dates back wellover 5000 years, and is now a sophisticated and highlycontrolled manufacturing process; yet the principle ofburning clay, to convert it from its natural plastic stateinto a dimensionally stable, durable, low-maintenanceceramic material, remains unchanged.

The quarrying of clay and brick manufacture arehigh-energy processes, which involveconsiderable quantities of carbon diopollutants including sulphur dioxidtion of clay also has long-term enviroalthough in some areas former claybeen converted to bird sanctuaries oational use. However, well-constructeda long life with low maintenance, anuse of Portland cement mortar prevenof individual bricks, the crushed materrecycled as aggregate in further constr

The elegant cathedral at Evry neardesigned by Mario Botta, illustrates thebrickwork.The cathedral of SaintCorb670,000 bricks, was dedicated in 199exhibits ne detailing both internallyExternally the cylindrical form risestrees. Internally the altar is surmoubelled structure leading ones view ucentral rooight. Three-dimensionalwork is nely detailed to generate theresponse.

Clay bricksThe wide range of clays suitable for brick making inthe UK gives diversity to the products available. Thisvariety is further increased by the effects of blendingclays, the various forming processes, the applicationof surface nishes and the adjustment of ring con-ditions. Earlier this century most areas had their ownbrickworks with characteristic products; however, easeof road transportation and continuing amalgamationswithin the industry have left a reduced number of

smaedh a gopeadencks a

makaryiminsouxfoCamclayces, lowturee strRedsellolaysthe emission ofxide and othere. The extrac-nmental effects,pits have nowr put to recre-brickwork has

d although thets the recyclingial is frequentlyuction.Paris (Fig. 1.1),modern use of

inian, builtwith7. The buildingand externally.to a circle of

nted by a cor-pwards to theinternal brick-desired acoustic

major producers and only a fewworks. Most UK bricks are den(HD) red-claymasonry units witgreater than 1000 kg/m3. The EurEN 771-1: 2003) also refers to lowclay masonry units, and these bloChapter 2.

The main constituents of brick-ica (sand) and alumina, but with vchalk, lime, iron oxide and othersuch as reclay, according to theirUK manufacturer uses the Lower Ofordshire, Buckinghamshire andproduce the Fletton brick. Thiscarbonaceous content that redufuel required to burn the bricksproducing a rather porous strucularly characteristic bricks are thStaffordshire Blues and Accringtontaining high iron content and the yfrom the Essex and Kent chalky ccontent.ll independentas high densityross dry densityn standard (BSsity (LD) red-re described in

ing clays are sil-ng quantities ofor constituentsrce. The largestrd clays of Bed-bridgeshire tocontains somethe amount ofering cost and. Other partic-ongly colouredfrom clays con-w London stockswith lower iron

2 M A T E R I A L S F O R A R C H I T E C T S A N D B U I L D E R S

Fig. 1.1 Brick construction Evry Cathedral, Ess

SIZE

Within Europe, the dimensions of clay(BS EN 771-1: 2003) have not been stin the UK, the standard metric brick reNational Annex (informative) to BS Eis 215 102.5 65mm, although thspecied requirement. Dimensions aorder, length, width and height, respUK dimensions match those in BS 47relates to special shapes and sizes of bdard brick weighs between 2 and 4 kg, ain one hand. The length (215mm) is ewidth (102.5mm) plus one standard 1three times its height (65mm) plus two(Fig. 1.2).

The building industry modular co-tem (BS 6750: 1986) is based on the100mm and multimodules of 3M, 630M and 60M. For metric brickwork

ses oghtnatepesnrythemene cark se appy un: 20onne, France. Architect: Mario Botta. Photographs: Arthur Lyons

masonry unitsandardised, butferred to in theN 771-1: 2003is size is not are given in theectively. These29: 2005, whichricks. The stan-nd is easily heldqual to twice its

is 3M or 300mm. Thus four courwork with joints give a vertical heifour stretchers with joints co-ordi

Table 1.1 illustrates the two tytolerance limits set for clay masothe metric brick, which relate tothe work size dimension. Measurea random sample of ten bricks. Thon the use of the square root of wothedimensional tolerance limits arwide range in size of clay masonrthe European Union (BS EN 771-10mm joint andstandard joints

ordination sys-module (M) ofM, 12M, 15M,, the base unit

Tolerances

Mean valueTolerance limits are set for the differenstated work size (e.g. 215, 102.5 anthe measured mean from the samplthe three brick dimensions (length, widf 65mm brick-of 300mm, andto 900mm.of dimensionalunits includingsquare root ofts are based onlculation basedize ensures thatropriate for theits used within03).ce between thed 65mm) andes, for each ofth and height).

B R I C K S A N D B R I C K W O R K 3

Fig. 1.2 Brick and co-ordinating sizes

These are categorised as T1, T2 and Tm where Tm is atolerance quoted by the manufacturer.

T1 0.40 (work size dimension) mm or3mm if greater

T2 0.25 (work size dimension) mm or2mm if greater

Tm deviation in mm declared bturer

RangeThe maximum range of size for any dimension isdesignated by categories R1, R2 and Rm.

R1 0.6(work size dimension) mm

n) mmthe manufacturer

Table 1.1 Tolerances on brick sizes

Brick (work)dimensions (mm)

Maximum deviatideclared work dim

f

T1

Length 215 6Width 102.5 4Height 65 3

Note: Limits for Tm and Rm are as declared by the my the manufac-R2 0.3 (work size dimensioRm range in mm declared by

on () of mean fromension (mm)

Maximum range of size within sample oten bricks (mm)

T2 Tm R1 R2 Rm4 * 9 4 *3 * 6 3 *

2 * 5 2 *

anufacturer (these may be wider or closer than the other categories).


Fig. 1.3 Linear bricks. Photographs: Courtesy of Ibstock Brick Ltd.

There is no direct correlation between the limits onmean value (T) and those for the range (R); thus,a brick conforming to category T2the wider range R1. Category R2 bricrequired for very tight dimensional conruns of brickwork.

Alternative sizes

The metric standard evolved from thImperial sizes, which varied signicant

were 94 382 78 in (229 112 73mmin (219 105 67mm). Some manufrange of bricks to full Imperial dimetively to an appropriate height (e.g. 50or 80mm) for bonding in to Imperiarestoration and conservation work.

The 1970s also saw the introductionular bricks with co-ordination sizes o300mm in length, 100mm in width a100mm in height. The popularity ofnow declined but they did give the arcnities for increasing or reducing horizand scale within the context of traditio

A recent development has beenof longer bricks to offer enhanced h

brick facades (Fig. 1.3). Lengths up to 440mm areavailable in a range of colours and textures for nor-

alteationand

the

racts traade rethemay be withinks may only betrol, as in short

e slightly largerly, but typically

) or 8 584 182 58acturers offer ansions, alterna-, 68, 70, 73, 76l brickwork for

of metric mod-f either 200 ornd either 75 orthese bricks hashitect opportu-ontal emphasisnal brickwork.the productionorizontality to

mal, quarter or third bonding,bonding in non-load-bearing situ240 115 50mm and 290, 327and 65mm.

MANUFACTURE OF CLAY BRICKS

There are ve main processes inclay bricks:

extraction of the raw material; forming processes; drying; ring; packaging and distribution.

Extraction of the raw material

The process begins with the extmaterial from the quarry and itthe works, by conveyor belt or rosoil and unsuitable overburden arused for site reclamation afterremoved.rnatively stacks. Sizes include440 102 50

manufacture of

ion of the rawnsportation totransport. Top-moved rst andusable clay is


Fig. 1.4 Moulds for handmade bricks

The raw material is screened to remove any rocks,then ground into ne powder by a series of crushersand rollers with further screening to remove any over-size particles. Small quantities of pigments or otherclays may be blended in at this stage to produce vari-ous colour effects; for example,manganproduce an almost black brick and rebrown effect. Occasionally, coke breezthe clay as a source of fuel for the ringdepending on the subsequent brick foup to 25% water may be added to giplasticity.

Forming processes

Handmade bricksThe handmade process involves the thrably sized clot of wet clay into a wooa bench. The surplus clay is struck ofwire and the greenbrick removed. The bare irregular in shape with soft arrises afolded surfaces. Two variations of the pmoulding and slop moulding.

In pallet moulding, a stock board,bed face of the brick, is xed to the bents loosely over the stock board, andheight to give appropriate thickness toThe mould and board are sanded tof the green brick which, is produced

depression on one face. In the case of slop moulding,the stock mould is placed directly on the bench, and isusually wetted rather than sanded to allow removal ofthe green brick which, unlike the pallet moulded brick,is smooth on both bed faces (Fig. 1.4).

beenicaay ismo

of thricks

Flejecteuldshaveurinpliedhe suxtur

y hitic parequirese dioxidewillclay gives a teake is added intoprocess. Finally,rming process,ve the required

owing of a suit-den mould onf with a framedricks producednd interestinglyrocess are pallet

the size of thech. The mouldis adjusted in

the green brick.o ease removalwith a frog or

Soft mud processThe handmade process has nowmated, with the clay being mechapre-sanded moulds; the excess cland the bricks released from themud process bricks retain muchassociated with true handmade bcost.

Pressed bricksIn the semi-dry process used forappropriate quantity of clay is subof four pressings within steel mogreen brick. These bricks usuallyone bed face. For facing bricks, texters and one stretcher may be aprollers. A water spray to moisten tby a blast of a sand/pigment misand-faced nish.

With clays that require a slightltent for moulding, the stiff plasin which brick-size clots of claymoulds. A single press is then ren largely auto-lly thrown intothen removeduld. These softe individuality, but at a lower

tton bricks thed to a sequenceto produce thea deep frog ong onboth head-by a series ofrface, followed

e, produces the

gher water con-rocess is usedforced into theed to form the


Fig. 1.5 Extruding wire-cut bricks

brick. Engineering bricks made by this process oftenhave shallow frogs onbothbed faces. In all cases the sizeof the mould is calculated to allow for the anticipateddrying and ring shrinkage.

Extruded wire-cut bricksIn this process clay with a water content of up to 25%is fed into a screw extruder which consolidates the clayand extracts the air. The clay is forced through a die andforms a continuous column with dimensions equal tothe length and width of a green brick (Fig. 1.5). Thesurfacemay then be textured or sanded, before the claycolumn is cut into brick units by a series of wires. Thebed faces of wire-cut bricks often show the drag markswhere the wires have cut through the extruded clay.Perforated wire-cut bricks are produced by the incor-poration of rods or tines between the screw extruderand the die. The perforations save clay and allow fora more uniform drying and ring of the bricks with-out signicant loss of strength. Thermal performance

is not signicantly improved by the incorporation ofvoids.

Drying

To prevent cracking and distortion during the ringprocess, green bricks produced from wet clays must beallowed to dry out and shrink. Shrinkage is typically10% on each dimension depending upon the moisturecontent. The green bricks, laid in an open chequer-work pattern to ensure a uniform loss of moisture, arestacked in, or passed through, drying chambers whicharewarmedwith thewaste heat from the ring process.Drying temperatures and humidity levels are carefullycontrolled to ensure shrinkage without distortion.

Firing

Both intermittent and continuous kilns are used forring bricks. The former is a batch process in whichthe single kiln is loaded, red, cooled and unloaded.In continuous kilns, the ring process is always active;either the green bricks aremoved through a xed ringzone, or the re is gradually moved around a series ofinterconnecting chambers to the unred bricks. Bothcontinuous systems are more energy efcient than theintermittent processes. Generally, for large-scale pro-duction, the continuous tunnel kiln (Fig. 1.6) and theHoffman kiln (Fig. 1.7) are used. Clamps and intermit-tent gas-red kilns are used for the more specialisedproducts. Depending on the composition of the clayand the nature of the desired product, ring tem-peratures are set to sinter or vitrify the clay. Colourvariations called kiss-marks occur where bricks werein contact with each other within the kiln and areparticularly noticeable on Flettons.

Tunnel kilnIn the tunnel kiln process the bricks are loaded 10 to14 high on kiln cars which are moved progressively

Fig. 1.6 Tunnel kiln


Fig. 1.7 Hoffman kiln plan

through the preheating, ring and cooling zones. Acarefully controlled temperature prole within the kilnand an appropriate kiln car speed ensure that the greenbricks are correctly red with the minimum use offuel, usually natural gas. The maximum ring temper-ature within the range 940C to 1200C depends onthe clay, but is normally around 1050C, with an aver-age kiln time of three days. The oxygenthe atmosphere of the kiln will affecthe brick products. Typically a high telow oxygen content are used in theblue bricks. A higher oxygen content woxide within the clay red.

Hoffman kilnIntroduced in 1858, the Hoffman kilnkiln in which the re is transferred arochambers which can be interconnecteing of dampers. There may be 12, 16 oalthough 16 is usual. The chambers areically 100,000 green bricks. The chamthe re, as it moves around, are prehring takes place (9601000C), foling, unloading and resetting of thesequence moves on one chamber perdays of burning. The usual fuel is naturlow-grade coal and landll methane armanufacturers.

Intermittent gas-red kilnsIntermittent gas-red kilns are frequening smaller loads, particularly specials

green bricks are stacked onto a concrete base and amobile kiln is lowered over the bricks for the ring pro-cess. The ring conditions can be accurately controlledto match those within continuous kilns.

ClampsThe basis of clamp ring is the inclusion of coke breezeinto the clay, which then acts as the major source ofenergy during the ring process. In the traditional pro-cess, alternate layers of unred bricks and additionalcoke breeze are stacked up and then sealed over withwaste bricks and clay. The clamp is then ignited withkindling material and allowed to burn for two to veweeks. After ring, the bricks are hand selected becauseof their variability fromunder- to over-red. Currentlysome handmade bricks are manufactured in gas-redclamps which give a fully controlled ring process butstill produce bricks with the characteristic dark patcheson their surfaces due to the burnt breeze content.

Packaging and distribution

Damaged or cracked bricks are removed prior to pack-ing. Most bricks are now banded and shrink-wrappedinto packs of between 300 and 500, for easy trans-portation by forklift truck and specialist road vehicles.Special shapes are frequently shrink-wrapped onto

necto fandnimEuro1: 20ens

tiongth aparequity, dtherre mty.e cladesc

amcontent withint the colour ofmperature andmanufacture ofill turn any iron

is a continuousund a series ofd by the open-r 24 chambers,lled with typ-bers in front ofeated, and thenlowed by cool-next load. Theday, with threeal gas, althoughe used by some

tly used for r-. In one system,

wooden pallets.

SPECIFICATION OF CLAY BRICKS

To specify a particular brick it iscertain key criteria which relateand appearance. The European St1: 2003 requires an extensive mifor masonry units, including thenumber and date (e.g. BS EN 771-unit (e.g. high density - HD), dimances from mean value, congurafrogged brick), compressive strenresistance. Also, depending on theadditional description may be ras appropriate, include dry densierance range, water absorption,active soluble salt content, moistution to re and vapour permeabili

Within the building industry thally also includes some traditional

place of origin and particular nshire smooth blue);essary to deneorm, durabilityard BS EN 771-um descriptionpean Standard03), the type ofions and toler-(e.g. a solid ornd freeze/thawticular end use,red. This may,imensional tol-mal properties,ovement, reac-

ssication usu-riptions:

e (e.g. Stafford-


clay composition (e.g. Gault, Weald or LowerOxford Clay, Etruria Marl, Keuper Marl [MercianMudstones] or shale);

variety typical use (e.g. Class A engineering,common or facing);

type form andmanufacturing process (e.g. solid,frogged, wire cut);

appearance colour and surface texture (e.g. coralred rustic).

Variety

Bricks may be described as common, facing or engi-neering.

Common bricksCommonbricks haveno visual nish, and are thereforeusually used for general buildingwork especially wherethe brickwork is to be rendered, plastered or will beunseen in the nished work.

Facing bricksFacing bricks are manufactured and selected to givean attractive nish. The particular colour, which maybe uniform or multicoloured, results from the blendof clay used and the ring conditions. Additionally,the surface may be smooth, textured or sand-facedas required. A slightly distressed appearance, similarto that associated with reclaimed bricks, is obtainedby tumbling either unred or redrotating drum. Facing bricks are usedbrickwork where a pleasing and durequired.

Engineering bricksEngineering bricks are dense andspecic load-bearing characteristicsabsorption. The National Annex NAto BS EN 771-1: 2003 relates the prtwo classes (A and B) of clay enginetheir minimum compressive strengths,centage water absorption, freeze/thawsoluble salt content (Table 1.2). Engare used to support heavy loads, and awhere the effects of impact damage, wor chemical attack need to be minimgenerally reds or blues and more expenmachine-made facing bricks becausering temperature.

Table 1.2 Properties of clay engineering bricks

Physical property Clay engineering bricks

Class A Class B

Dened propertiesMinimum compressive strength (MPa) 125 75Maximum water absorption (% by mass) < 4.5 < 7.0

(and DPC1) (and DPC2)Typical additional propertiesNet dry density (kg/m3) 2200 2100Freeze/thaw resistance class F2 F2Active soluble salt content class S2 S2

Note:The water absorption limits for all clay bricks used for damp-proofcourses for buildings (DPC1) and external works (DPC2) are included in thetable.

Type

Type refers to the formof the brick anddeneswhetherit is solid, frogged, cellular, perforated or of a spe-cial shape (Figs. 1.8 and 1.9). Bricks may be froggedon one or both bed faces; perforations may be fewand large or many and small. Cellular bricks havecavities closed at one end. Keyed bricks are used togive a good bond to plaster or cement rendering.Because of the wide range of variation within bricktypes, the manufacturer is required to give details ofthe orientation and percentage of perforations in all

her resistance ande laid with the frogspletely lled with

cks the deeper frogor cheapness, speedbricks within afor most visualrable nish is

vitreous, withand low water(informative)

operties of theering bricks tomaximum per-resistance and

ineering brickslso in positionsater absorptionised. They aresive than otherof their higher

cases.For maximum strength, weat

sound insulation, bricks should buppermost so that they are commortar; with double-frogged brishould be uppermost. However, f

Fig. 1.8 Brick types


and possibly minimisation of the dead weight of con-struction, froggedbricks are frequently laid frog-down.Inevitably this leads to a resultant reduction in theirload-bearing capacity.

Standard specials

Increasingly, specials (special shapes) are being used toenhance the architectural quality of brickwork. British

Fig. 1.9 Specials. Photograph: Courtesy of Ibstock Brick Ltd.

1 0 M A T E R I A L S F O R A R C H I T E C T S A N D B U I L D E R S

Fig. 1.9 (continued)

B R I C K S A N D B R I C K W O R K 1 1


Standard BS 4729: 2005 illustrates the range of stan-dard specials, which normally can be made to order tomatch standard bricks (Fig. 1.9).

Designation of standard specials:

Angle and cant bricksBullnose bricksCopings and cappingsPlinth bricksArch bricksRadial bricksSoldier bricksCuboid bricksBonding bricksBrick slips

Manufacturers also frequently makespecials (special specials) to the particulof the architect or builder. Inevitably, dcials takes longer than for ordinary bseparate ring frequently leads to somation between the specials and the seven where the clay used is identical.plex specials are handmade, usually instock moulds, although some can beifying standard bricks before ring.shapes includes copings and cappingand freestanding walls), bullnose (for

e.g. window and door reveals), plinths (for corbellingdetails and cills), cants (for turning angles), arches andbrick slips (to mask reinforced concrete lintels etc.).Special bricks are also manufactured by cutting stan-

dingtagebrisetsme

ly brmenal t

factompink, deons,r thniforr vaomge frldedpurpose-madear requirementselivery on spe-ricks, and theire colour vari-

tandard bricks,The more com-specially shapedmade by mod-The range of

s (for parapetscorner details,

dard bricks, then, if necessary, bonepoxy resins. This has the advanexact colour match to the standardslips, dog leg and arch voussoirate an arch) are produced by thisbrick cutting companies also suppvation projects as in the refurbishfacade of St Pancras InternationLondon.

APPEARANCE

The colour range of bricks manuis extensive. The colours range frgreys and yellows through pastelblues, browns and deep blue/blackon the clay and the ring conditiaddition of pigments to the clay oa sand facing. Colours may be uthe surface of individual bricks oto brick. The brick forms vary frwith rounded arrises; textures ransanded to textured and deeply fothe forming process (Fig. 1.10).the pieces withof ensuring ancks. Many brick(bricks to cre-thod. Specialisticks for conser-t of the elegantrain station in

ured in the UKthe light buffs,to strong reds,

pending mainlybut also on thee application ofm, varied overried from brickprecise to thoseom smooth and, depending on


Fig. 1.10 Typical range of clay brick textures and colours. Photographs: Courtesy of Ibstock Brick Ltd.


Fig. 1.11 Handmade Hoskins Bromley Red bricks. Photograph: Arthur Lyons

In view of the variability of bricks from batch tobatch it is essential that they should be well mixed,preferably at the factory before palleting, or failing this,on site. If this is not done sufciently, accidental colourbanding will appear as the brickwork proceeds. Sand-faced bricks are liable to surface damage on handling,which exposes the underlying colouChipping of the arrises on bricks withis visually less detrimental. Where rainan important factor, e.g. on cills and crather than heavily rusticated bricks shthe latter would saturate and stain. Hawith deep surface folds (Fig. 1.11) shoup so that the creases or smiles tend towater from the face of the brickwork.

Glazed bricks, available in a wide rcolours, are sometimes used for theireffect (Fig. 1.12) or resistance to graftimanufactured in a two-stage process,the initial ring of the green brick to tfollowed by the application of a slip glaring. In the alternative one-stage pris applied before a single ring. Mana standard range of colours or the opfrom the RAL colour range. Bricks maytially glazed and special shapes are noto order.

The visual acceptability of facingquality of the bricklaying would normon site by the construction of a refereleast 1m2 to the standardPAS 70: 2003,

selected bricks with examples of any colour banding,the proposed bonding, mortar and jointing. All sub-sequent brick deliveries and constructed brickworkshould then be checked against the reference panel.

DURABILITY

he three categories,ost resistance withinle 1.3). Only cate-to repeated freezingd condition. Cate-pt when subjectedg under saturated

sistance and active soluble

esistance

ected to severe exposureected tected t

salts

sium

sium

ntr of the brick.through colour

water run-off isopings, smoothould be used, asndmade bricksuld be laid frogshed the rain-

ange of intensestrong aesthetic. They are eitherwhich involveshe biscuit stage,ze and a secondocess, the glazeufacturers offertion to specifybe fully or par-

rmally available

bricks and theally be assessednce panel of atusing randomly

Frost resistance

Bricks are classied into one of tF2, F1 and F0 according to their fra standardised freezing test (Tabgory F2 bricks are totally resistantand thawing when in a saturategory F1 bricks are durable, exceto repeated freezing and thawin

Table 1.3 Designation of freeze/thaw resalt content for clay bricks

Durability designation Freeze/thaw r

F2 Masonry subjF1 Masonry subjF0 Masonry subj

Active soluble

S2 Sodium/potas0.03%

S1 Sodium/potas0.08%

S0 No requiremeo moderate exposureo passive exposure

content

0.06%, magnesium

0.17%, magnesium


Fig. 1.12 Glazed bricks. Selection of colours and

conditions. Therefore, category F1 brbe used in highly exposed situationsdamp-proof courses, for parapets orcopings, but they are suitable for exterAtlantic House, London. Architects: Proun Architects. Photographs: Courtesy

icks should notsuch as belowbrick-on-edge

nal walls which

are protected from saturation by apping. Category F0 bricks must only be uare subject to passive exposure, as whcladding or used internally.of Ibstock Brick Ltd.

ropriate detail-sed where theyen protected by


Soluble salt content

The soluble salt content of bricks is dened by threecategories: low (S2), normal (S1) and no limits (S0)(Table 1.3). Both the S2 and S1 categories have denedmaximum limits for sodium/potassium and magne-sium salt contents. The soluble salts derive from theoriginal clay or from the products of combustionduring the ring process. Soluble salts can cause efo-rescence and soluble sulphates may migrate from thebricks into the mortar or any rendering, causing it toexpand and deteriorate by sulphate attack. If used inan exposed situation, S1 and S0 category bricks shouldbe bonded with sulphate-resisting cement mortar.

Eforescence

Eforescence sometimes appears as a white deposit onthe surface of new brickwork (Fig. 1.13). It is caused bymoisture carrying salts from inside the bricks andmor-tar to the surface where the water evaporates leavingthe crystalline salts. Under most conditions it disap-pears without deleterious effect within one year. Inexposed brickwork that is constantly subjected to acycle of wetting and drying, eforescence can occurat any time; further, a build-up and expansion ofcrystalline salts under the surface (crypto-eforescence)may cause the face of the brickwork to crumbleor spall.

Staining

The surface of brickwork may be stained by cementduring the building process, or by lime leaching out ofthe fresh mortar (Fig. 1.14). In either case the excessshould be brushed and washed off, without saturatingthe brickwork.

PHYSICAL PROPERTIES

Compressive strength

Highdensity (HD) clay bricks are availablewith a rangeof compressive strengths from around 5MPa to wellover 100MPa. The criteria for general use, damp-proofcourses and engineering use are set out in Table 1.2(page 8).

To determine the crushing strength of bricks, bothbed faces are ground down until at and parallel. Thebricks are then crushed without lling the voids orfrogs. Where frogs are to be laid upwards and lled inthe construction, the crushing strength (MPa) is basedon the net bearing area. Where frogs or voids are notto be lled, the crushing strength is based on the fullgross area of the bed face.

Water absorption and suction

The level of water absorption is critical when bricksare to be used for damp-proof courses, or as engineer-ing bricks. Appropriate limits are shown in Table 1.2,

Fig. 1.13 Eforescence


Fig. 1.14 Lime leaching on brickwork

although generally absorption ranges frSuction rates are now quoted by mufacturers, as high values can advebricklaying process. Bricks with higabsorb water rapidly from themortar,ciently plastic to allow for repositionias the work proceeds. Generally low otion rates (1.02.0 kg/m2 per min) areInwarmweather, high-suction-rate brited in clean water before laying, but awill cause the brick to oat on the malso increase the risk of subsequent efstaining.

Moisture and thermal movement

After the ring process, bricks absorbthe atmosphere and expand irreversiblmum of 0.1%. It is therefore recommenshould not be used for at least two w(although it is now recognised thatprocess may continue at a decreasiyears). Subsequent moisture and thermare largely reversible, and movement

f brce

wallld hal minterrdeternm sis pe

ry mefulpriadiffbetthicetailorllerm ruble.nd som1% to 35%.ost brick man-rsely affect theh suction ratesmaking it insuf-ng of the bricksr medium suc-advantageous.

cksmay bewet-ny excess waterortar bed and

orescence and

moisture fromy, up to a maxi-ded that bricks

eeks after ringthis irreversibleng rate for 20al movements

for a 1mm movement per 1m obe allowed, typically at 1012mmaximum of 15m, in restrainedor lightly restrained walls shoujoints at 78m centres. Horizontshould be at approximately 12mtical movement is of the same oin the horizontal direction. In exnon-load-bearing walls a maximubetween vertical movement jointsBS EN 1996-2: 2006).

For many buildings the necessacan be made inconspicuous by cartured as part of the design. Appromovement joints would be whereforms adjoin, such as abutmentscolumns or where the height orchanges; alternatively, at design dwork returns, re-entrant cornersdownpipes. In expansion joints, lar polythene, polyurethane or foaused, as these are easily compressibe with a exible sealing compoujoints allowing polysulphide.ickwork shouldntres and at as. Unrestrainedave movementovement jointsvals, as the ver-r as movemental unreinforcedpacing of 15mrmitted (NA to

ovement jointsdetailing or fea-te locations forering structuralween walls andkness of a walls such as brick-the recesses fors such as cellu-bber should be

Pointing shoulduch as two-part


Typical reversible moisture movement = 0.02%Typical reversible thermal movement = 0.03%Thermal movement = 58 106 deg C1

Thermal conductivity

The thermal conductivity of brickwork is dependenton its density and moisture content, but generallyclay bricks are poor thermal insulators. Brick manu-facturers quote thermal conductivities at a standard5% moisture content for exposed brickwork, and mayalso give the 1% moisture content gure for protectedbrickwork.

Using bricks with an average thermal conductiv-ity of 0.96W/m K, a typical partially lled cavity sys-tem is:

102.5mm fairfaced brickwork50mm clear cavity50mm foil-faced rigid polyurethane insulation(= 0.023W/mK)100mm lightweight blockwork (= 0.15W/mK)12.5mm plasterboard on dabs

giving a U-value of 0.27W/m2 K.

The thermal conductivity of clay bricks at 5%moisture content typically ranges1.95W/m K.

Fire resistance

Clay brickwork generally offers excetance by retaining its stability, integrityproperties. The standard (BS 5628-3:that 100mm and 200mm of load-bebrick masonry will give 120minutes aof re resistance, respectively. Bricks1% organic material are automaticallyEuroclass A1 with respect to reaction t

Acoustic properties

Good-quality brickwork is an effectivborne sound, provided that there are nthemortar for the passage of sound. Alshould be sealed and bricks laid withachieve the necessary mass per unit arpathways.

At the junction between a cavity brating wall and an external brick andif the external cavity is not fully lle

insulation, then the separating wall cavity must beclosed with a exible cavity stop to reduce soundtransmission sufciently to comply with the BuildingRegulations Part E performance requirements.

Impact sound absorption by brickwork over thenormal frequency range is fairly low and furtherdecreased by the application of dense plaster or paint.However, the application of acoustic plasters or theaddition of an independent panel of plasterboardbacked by absorbent material improves impact soundinsulation.

QUALITY CONTROL

Tomeet the consistent standards of quality required byclients, many brick manufacturers are now operatingquality assurance systems. These require manufactur-ers to document all their operational procedures andset out standards to which products must adhere.Quality is controlled by a combination of an internalself-monitoring system and two to four independentspot-check reviews per year. Both the content of thetechnical literature and the products themselves aresubjected to this scrutiny.

l noays wrickr dhavgulamenatelyathaivelyde vth 05in t

d footistanfrom 0.65 to

llent re resis-and insulating2005) indicatesaring solid claynd 360minuteswith less thancategorised as

o re.

e barrier to air-o voids throughlmasonry jointslled frogs to

ea and avoid air

lockwork sepa-blockwork wall,d with thermal

Unred clay bricksUnred clay bricks for internaapplications are produced from clless suitable for standard red brequire only low energy input fohigh potential recyclability. Theyof inhibiting condensation and rehumidity of the internal environshould be laid with clay or modermortar and nished with a breas clay or lime plaster, alternatpermeable paint. Products inclurated bricks with keyed or smoo220 105 67mm and 220 11.15). Compressive strengths are3.8MPa.

Reclaimed clay bricksReclaimed bricks are often selectesons, but their appearance is ndurability. In particular, frost resn-load-bearinghich would be

s. Earth bricksrying and havee the advantageting the relativet. Earth brickshydraulic lime

ble nish suchlime wash or

ertically perfo-nishes to sizes133mm (Fig.

he range 2.9 to

r aesthetic rea-a guarantee ofce is uncertain


Fig. 1.15 Unred clay brick and block. Photographs: Courtesy of Ibstock Brick Ltd.

and it is not valid to test a sample to classify thewhole consignment. Imperial sizes may vary con-siderably and some material may be contaminatedwith sulphates, or be liable to eforescence fromabsorbed soluble salts. However, the strength andwater absorption properties of reclaimed bricks areusually appropriate for domestic-scale construction.Reclaimed paving bricks that have previously beenexposed to frost will normally be durable, but wallingbricks may not be durable when used as pavers.

Recently some buildings have been constructedusing limemortar, specicallywith a vitial recycling of the metric bricks atuseful life of the construction. Limenicantly easier to clean from brickPortland cement mortar.

Of the estimated 2500 million brieach year in the UK only about 5% arnearly half are crushed and used as har

BrickworkCLAY BRICKWORK

The bonding, mortar colour and joinsignicant visual effect onbrickwork. Tcan be to emphasise as a feature or remum the impact of the bonding mortaAdditionally, the use of polychromaticcomplementary or contrasting coloureveals, banding and even graphic dea dramatic effect on the appearance ofthree-dimensional effects of decorativand projecting corbelled features off

further opportunities to exploit the effects of light andshade.Normally, a projection of 1015mm is sufcientfor the visual effect without causing increased suscep-tibility to staining or frost damage. Curved brickworkconstructed in stretcher bond shows faceting and theoverhang effect, which is particularly accentuated inoblique light. With small-radii curvatures, the neces-sary change of bonding pattern to header bond canalso be a visual feature, as an alternative to the use ofcurved-radius bricks.

The Gothic Revival exterior of the Queens Building,r (Fromy-ef, heallsatc

visuaof plr andfea

lles aing auffd-br

ireda sr thsequthe baffee baew to the poten-the end of themortar is sig-

s than modern

cks demolishede reclaimed anddcore ll.

t prole have ahe overall effectduce to a mini-r on the bricks.brickwork withrs for quoins,signs can havea building. Thee dentil courseser the designer

De Montfort University, Leicestetrates the visual effects of polychand voussoir specials. The energmaximises use of natural lightingtilation, using massive masonry wtemperatures. The mortar, which mcoral-red brickwork, reduces theindividual bricks, giving the effectwalls. This is relieved by the colouof the polychromatic and corbelledincorporated in the ventilation grispecial bricks, cill details and banda deeper cadmium red and silver bthe characteristic Leicestershire re

Mortars

The mortar in brickwork is requing for the bricks and act asthem. Mortars should be weakeual bricks, to ensure that any subdoes not cause visible cracking oftoo weak a mix would adverselythe brickwork. Mortar mixes arig. 1.16), illus-atic brickworkcient buildingating and ven-to reduce peakhes the externall impact of theanes rather thanshadow effects

tures, which arend towers. There picked out into contrast withick colouring.

to give a bear-ealant betweenan the individ-ent movementricks, althoughct durability ofsed on blends


Fig. 1.16 Decorative brickwork Queens Building, De Montfort University, Leicester. Architects: Short Ford & Associates. Photograph: ArthurLyons

of either cement/lime/sand, masonry cement/sand orcement/sand with plasticiser. Suitable alternatives toPortland cement are listed in Table 1.4 to PD 6678:2005.When themix is gauged by volume, an allowancehas to be made for bulking of damp sand. Theve mix classes are shown in Table 1.5. A typical1 : 1 : 6 (cement : lime : sand) mix (M4designation(iii)) would generally be appropriate and durablefor low-rise construction, but for calculated struc-tural brickwork or for increased resistance to frost inexposed situations a greater-strength mortar may be

Table 1.4 Appropriate cements for mortars (P

Cement Standard

Portland cement BS EN 197-1Sulphate-resisting Portland cement BS 4027Portland slag cement BS EN 197-1Portland y ash cement BS EN 197-1Portland limestone cement BS EN 197-1Masonry cement (inorganic llerother than lime)

BS EN 413-1

Masonry cement (lime) BS EN 413-1

required. For designed mortars to BS Ethe specication is performance-basethe compressive strength M in MPaprescribed mortars a combination ofproportions and the 28-day compresrequired. In the repointing of old brickwularly important to match the porositythe water-retention characteristics of tprevents excessive loss of water from thhydration occurs, which may then cauto crumble.

The use of lime mortar, as in the Buildine reucle. Tubb

y grnatewerjoriten th, 0/TypD 6678: 2005)

Cement notation

CEM I

CEM II/A-S or II/B-SCEM II/A-V or II/B-VCEM II/ALL(L)Class MC

Class MC

Establishment environmental buWatford, will allow for the ultimatat the end of the buildings life cybricks is not possible, except as rPortland cement mortar is used.

Sands for mortars are normall13139: 2002 into categories desigsieve sizes d/D which dene the lolimits in mm, respectively. The masize distribution should lie betweThe preferred grades are 0/1mm0/8mm, 2/4mm and 2/8mm.N 998-2: 2005,d in relation toat 28 days. Forthe constituentsive strength isork it is partic-of the brick to

he mortar. Thise mortar beforese the pointing

ilding Researchg in Garston,se of the brickshe recycling of

le, when strong

aded to BS ENd by a pair ofand upper sizey of the particlee stated limits.2mm, 0/4mm,ically between


Table 1.5 Mortar mix designations and classes

Mortar designation Mortar class Cement:lime:sand Masonry cement:sand Cement:sand with plasticiser

(i) M12 1:0:3 1 : : 3(ii) M6 1 : : 4 1 : : 4 : 1 : 2 1 : 3 1:3 1:4(iii) M4 1:1:5 1:1:6 1:4 1:5 1:5 1:6(iv) M2 1:2:8 1:2:9 1 : 5 1 : 6 1:7 1:8(v) M1 1:3:10 1:3:12 1 : 6 1:7 1:8

Notes:Mortar classes to BS EN 998-2: 2003 equate to compressive strengths at 28 days in MPa.M1 class is listed in BS EN 998-2: 2003, but not in BS 5628-3: 2005 or NA to BS EN 1996-1-1: 2005.Designations to BS 5628-3: 2005.

85 and 99% of the sand should pass through thelarger sieve limit, and between 0 and 20% should passthrough the smaller sieve size limit. The grades withmore nes (63 micron or less) require more cement toachieve the same strength and durability as the equiv-alent mortars mixed with a lower nes content.

Ideally, brickwork should be designed to ensurethe minimal cutting of bricks and built with a uni-form joint width and vertical alignment of the joints(perpends). During construction, brickwork shouldbe kept clean and protected from rain and frost. Thisreduces the risk of frost damage, patchiness and efo-rescence. Brickwork may be rendered externally orplastered internally if sufcient mechavidedby appropriate jointingor theuseFor repointing existing brickwork, itmatch carefully the mortar sand and uwhere it was used in the original const

Bonding

Figure 1.17 illustrates the effects ofstretcher bond is standard for cavitymally a half-lap bond is used, buthorizontal emphasis can be achieved bdard quarter or third bond. In consemay be necessary to use half bricks (smatch the appearance of bonding in sFor one-brick-thick walls more variable; most typical are the English andThe equivalent English andFlemish garwhich have more stretchers, are primone-brick-thick walls where the reduheaders makes it easier to build bothPanels of herringbonebrickwork (rakintooth and dentil courses as in Victoriangenerate interesting features.

In all cavity brickwork, wall ties manufactured fromgalvanised steel, stainless steel or polypropylene to BSEN 845-1: 2003 should be incorporated (Fig. 1.18).They should be installed according to BS 5628-3: 2005drip down and level or sloping down (25) towardsthe outer leaf. Wall ties are categorised as Types 1 to4 to BS 5628 according to their strength and appro-priate use, and lengths are dependent on the cavitywidth (Table 1.6). The Building Regulations refer onlyto types A and B. Type A are the normal butteryties, and Type B are double triangle ties. Stainless steelties are specied for all housing. An estimated mini-mum service life of 60 years is recommended by the

therctureesin

neranavitibationandmetr th

all tileaftyin

ffectwithort

rea.availith tnical key is pro-of keyedbricks.is necessary tose lime mortarruction.

bonding. Thewalls and nor-an increase iny the less stan-rvation work itnap headers) toolid brick walls.tions are possi-Flemish bonds.denwall bonds,arily used for

ced number ofsides fairfaced.g bond), or dogbrickwork, can

publication DD 140-2: 1987. Lowity wall ties are available, manufacomposite basalt bre and epoxy v

Where mortar bed-joints dobetween masonry leaves, slope-tolmust be used. In partially lled cshould clip the insulation cavityleaf. In all cases the cavity, insulatbe kept clear of mortar droppingsby using a protective board. Asymused for xingmasonry to timber oblockwork. Movement-tolerant wwithin a slot system xed to oneScrew-in wall ties are available forto existing walls.

Coloured mortars

Mortar colour has a profound eappearance of the brickwork, asand a standard 10mm joint, the m17% of the brickwork surface aof light-fast coloured mortars isbe used to match or contrast wmal conductiv-d in pultruded.ot co-ordinatet cavity wall tieses, the wall tiests to the innerand ties shouldother residues

ric wall ties arein-joint aircretees bend, or slideof the masonry.g new masonry

on the overallstretcher bondar accounts forA wide rangeable which canhe bricks, thus


Fig. 1.17 Brick bonding

Fig. 1.18 Wall ties


Table 1.6 Wall ties to BS 5628-1: 2005

Types Least leafthickness (mm)

Nominal cavitywidth (mm)

Tie length(mm)

Types 1, 2, 3 or 75 75 2004 depending on 90 76100 225design loading 90 101125 250and cavity width 90 126150 275

90 151175 30090 176300 50 mm embedding

in each leaf

Notes:Type 1Masonry: Heavy duty. Suitable for most masonry constructionexcept where large differential movements are anticipated.Type 2Masonry: General purpose. Suitable for construction up to 15 mabove ground level, when built of double leaves of similar thicknesses in therange 90150 mm. Maximum basic wind speed of 31 m/sec.Type 3Masonry: Basic. As Type 2 but for lower basic winds speeds of25 m/sec maximum.Type 4 Masonry: Light duty. Suitable for dwellings up to 10 m in height,when built of double leaves of similar stiffness and thicknesses in the range90150 mm. Suitable for most internal separating cavity walls.All specications are subject to verication by calculation.A minimum embedded length of 50 mm is required in each leaf.Wall ties in leaves of 90 mm or more should be placed at a minimumdensity of 2.5 ties per square metre. Thinner walls require increased provision.

highlighting the bricks as units or creating a unitywithin the brickwork. The coloured mortars containinert pigments, which are factory-blended to a tightspecication to ensure close colour matching betweenbatches. Occasionally, black mortars may bloom dueto lime migration to the surface. Coloured mortarscan be used creatively to enhance the visual impactof the brickwork and even create designs on sectionsof otherwise monochromatic brickwork. The quantityof pigment should not exceed 10% by weight of thecement.

Mortar colours may also be modiestains after curing; however, such ap

penetrate 2mm into the surface, and therefore tendto be used more for remedial work. Through-bodycolours are generally more durable than surface appli-cations.

Joint proles

The standard range of joint proles is illustrated inFig. 1.19. It is important that themain criterion shouldbe the shedding of water to prevent excessive satu-ration of the masonry, which could then deteriorate.Normally the brickwork is jointed as the constructionproceeds. This is the cheapest and best method as itgives the least disturbance to the mortar bed. Point-ing involves the raking out of the green mortar to adepth of 1320mm, followed by relling the joint withfreshmortar. This is only appropriate when the desiredvisual effect cannot be obtained directly by jointing; forexample, when a complex pattern of coloured mortarjoints is required for aesthetic reasons.

The square recessed (raked) joints articulate thebrickwork by featuring the joint, but these should onlybe used with durable, (F2, S2) high-absorption bricksunder sheltered conditions; furthermore, the recessshould be limited to a maximum depth of 6mm. Thestruck or weathered joint also accentuates the light andshade of the brickwork, while, as a tooled joint, offer-ing good weather resistance in all grades of exposure.If the visual effect of the joint is to be diminished,the ush joint may be used, but the curved recessed(bucket handle) joint, which is compressed by tooling,offers better appearance andweathering properties.Nomortar should be allowed to smear the brickwork, as itis difcult to remove subsequently without the use ofdilute acid or pressure jets of water.

Reinforced brickwork

ucedg. 1

Fig. 1.19 Joint prolesd by the use ofplications only

Reinforcement may be introdhorizontally into brickwork (Fivertically or.20). Bed-joint


Fig. 1.20 Reinforced brickwork

reinforcement, usually austenitic stainless steel, shouldbe completely surrounded by mortar with a minimumcover of 15mm. For continuity in long walls, sectionsof reinforcement should be sufcienVertical reinforcement is possible inpocket-type walls, where the void spain the brickwork, then reinforcemenis introduced after the masonry is cshould be taken in the use of vibratthe concrete within new masonry.

Decorative brickwork

Tile-bricks replicate the visual effectproled edge on each brick overhangsbelow creating the tiled effect. The br10mmmortar which is cut back 15mmface, using only a 1mm vertical jointappear to butt joint. A range of colouand sand-faced nishes is availablespecials for corner returns. The briccompleted in courses ahead of the blocthat internal vertical joints are sealed.are typically used for gable-ends on ho

Proled bricks (Fig. 1.21), which cstandard brickwork, can create featureshadow effects. Shapes include saw

pyramids and wave effects in a variety of colours andnishes to create feature panels or to be interspacedwithin standard brickwork.

ophtured forracotolidred ca mpedof

or mewinge bilt irtarcaron

h jothemm

jointglue-tly end lapped.the cavity or inces are formedt and concreteompleted. Careors to compact

of hung tiles. Athe brick courseicks are laid infrom the front

so that the tilesrs with smoothwith matchingkwork must bekwork to ensureThe tile-bricksusing.o-ordinate withs with enhancedtooth, spheres,

Plaques, motifs, murals and stures (Fig. 1.22) can be manufacdesigns both for new buildings anor refurbishment of Victorian terare carved as a bas-relief in soft sbrickwork or moulded in the unsmall units and joined on site withFor repetitive units, the clay is shaate wooden mould. Relief depthsshadow and contrast sufcient feffects to be seen, although the viangles must be considered. For lartures, the whole unit may be buwith allowances made for the moing contraction. The design is thendismantled, red and reassembled

Thin-bed masonry

The use of thin-bed masonry, wit2 and 6mm, signicantly reducesthe mortar joints from 17% in 10brickwork, to only 8% in 4mmfurther enhanced by the use ofisticated sculp-d to individualthe renovationta. The designsthrough-colourlay in relativelyatching mortar.in an appropri-1030mm giveost sculptural

g distances andrickwork sculp-n green bricks,joints and dry-ved, numbered,site.

ints of betweenvisual effect ofjoint standard

s. This effect ismortars which


Fig. 1.21 Proled bricks. Photographs: Courtesy of Ibstock Brick Ltd.

Fig. 1.22 Decorative carved brickwork. PhotoBaggeridge Brick Plc.graph: Courtesy of

are applied to create a recessed joint.becomes only a shade line and the viswall is totally determined by the coloof the bricks. Because the glue-mortartraditionalmortar andhas tensile propework patterns are not constrained to stabonding. The glue-mortar is appliedboth the horizontal and vertical jointsolid or perforated bricks rather thanare most appropriate. Thin-bed masonspecial aramid bed-joint reinforcemeappropriate. The system offers the crsignicant alternative aesthetic opport

Preassembled brickwork

The use of preassembled brickwork supforced concrete or steel frames offerpotentially higher level of quality contrspeed of construction on site (Fig. 1.2the scope to create complex details andlong low arches, that would be expensivin traditional brick construction. Spfacturers produce large complete briconcrete panels with either whole brickThus the jointual effect of theur and textureis stronger thanrties, the brick-ndard stretcherin two lines tos, and thereforefrogged bricksry wall ties andnt are used aseative designerunities.

ported on rein-s the builder aol and increased3). It also offersforms, such ase or impossibleecialist manu-

ck-clad precasts or brick slips.


Fig. 1.23 Preassembled brickwork. Photograph: Courtesy of Trent Concrete Ltd.

Typically the rear faces of brick slipan angle, then stainless steel rods inswith resin adhesive. The brick slips arspacers within the panel mould, priorof steel reinforcement and concrete. Fslips are pointed up giving the appearbrickwork.

Factory-made brickwork panels of sosions and single-storey height, incorpoand ducts for windows, doors and eletions, enable fast erection on site forconstruction. One manufacturer suppunits constructed on steel frames for eon site. The panels can either be preunnished for subsequent pointing on

Brick cladding systems

A signicant revolution for brick-facbeen the development of brick slipcladding systems, designed to haveand durability of traditional brickwosignicantly reduced construction timtem, external walls are constructed wiated concrete blockwork and faced wpolystyrene insulation panel to whicslips are applied onto the pre-form

naln ovnd ahesips atalun oleof c/m2.

athebricpria: 6

d offangs, pranck isg stare-faconre-fo

slipkwos are drilled aterted and xede laid out withto the additioninally the brickance of normal

lidwall dimen-rating openingsctrical installa-domestic-scale

lies bay windowasy installation-pointed or leftsite.

ed building hasand brick tile

the appearancerk, but with ae. In one sys-

th 215mm aer-ith an extrudedh 16mm bricked grid, giving

the appearance of standard exterThe polystyrene grid panels have ahorizontal joints are watertight agrooved to interlock vertically. Adthe polystyrene and the brick sliplace with the appropriate horizonis applied with either a pointing gand tooled to the required joint prohighly insulating blocks, this typeachieve U-values as low as 0.27W

An alternative system usesgalvanised-steel prole xed to(Fig. 1.24). The specially shapedinto the steel system with approspacing. Mortar (typically a 1 : 1with a pointing gun and smootheprole, usually bucket-handle. A ris manufactured to produce dadoexternal returns, giving the appeabrickwork. Because the brickwora range of bond patterns includindiagonal is optional. This type of pthe potential for increased off-siteand some manufacturers supply ppanels ready for xing on site.

Another use for 20mm brickrefurbishment of poor-quality bricleaf brickwork.erlap to ensurere tongued andve is applied tore pushed intospacing. Mortarr a mortar bag

.With the use ofonstruction can

plastic-coatedstructural wallk tiles then clipte vertical jointmix) is appliedto the requirede of special tileslinths, cills ande of traditionalnon-structural,ck, quarter andbrication offersstruction work,rmed brick-tile

systems is therk or previously


Fig. 1.24 Brick cladding system. Photograph: Co

rendered blockwork, giving an enhanaesthetic of fairfaced brickwork.

CLAY BRICK PAVING

Many clay brick manufacturers prodplain and chamfered paving bricks tmatching range of paver accessories. Bpaving are frequently nibbed to set trectly. The material offers a human scaof hard landscape, especially if creativepattern and colour. Typical patterns (Fherringbone, running bond, stack bonand the use of borders and bands. Hobe noted that not all paver sizes co-oringbone and basket-weave designs.designs include decorative diamond anpatterns, and pedestrian-managementpaving bricks may be laid on a hard bjoints or alternatively on a exible basbrushed between the pavers. Edge restrto prevent lateral spread of the units.

The British Standard (BS EN 1344:minimum paver thicknesses of 40mm

spectively. However,r exible laying andubjected to substan-01). Table 1.7 showsre classied on theers with designationfreezing conditions,ay be used underdard BS EN 1344:tegoithr rigave

surtesy of Corium, a division of Baggeridge Brick Plc.

cement to the

uce a range ofogether with aricks for exiblehe spacing cor-le to large areasuse is made of

ig. 1.25) included, basket-weavewever, it shouldrdinate for her-Proled brickd chocolate-bartexturing. The

ase with mortare with ne sandaint is necessary

exible and rigid construction, re50mm pavers are generally used fo60mmpavers are necessarywhen stial vehicular trafc (BS 7533-1: 20the standard sizes. Clay pavers abasis of freeze/thaw resistance. PavFP0 are unsuitable for saturatedwhile pavers designated FP100 mfreeze/thaw conditions. The Stan2002 classies pavers into ve caof transverse breaking strength, wgory T0 being appropriate only foSlip resistance for the unpolished p

Table 1.7 Standard work sizes for paver

Length (mm) Width (mm)

215 102.5215 102.5210 105210 1052002) stipulatesand 30mm for

200 100200 100ries (T0 to T4)the lowest cate-id construction.rs is categorised

Thickness (mm)

50655065

5065


Fig. 1.25 Typical range of clay pavers and hard landscape at Birmingham. Photographs: Courtesy of Baggeridge Brick Plc.



as high, moderate, low or extremely low. This factorneeds to be considered particularly for potentially wetconditions to ensure safe pedestrian and trafc usage.The standard BS 7533 (Parts 1, 2, 3, 9 and 13) describesthe design for heavy- and light-duty pexible, rigid and permeable pavementrespectively.

Calcium silicate bricksCalcium silicate bricks, also knownintlime bricks, were rst producedin Germany in 1894, and then in thInitially their use was conned toapplications, but in the 1950s, theirfoundations was exploited. Research iand the development of improvedmancesses subsequently led to the productioof load-bearing-strength classes and atCalcium silicate bricks are competitivhave about 3% of the UK brick marke

SIZE

The work size for calcium silicate b102.5 65mm, the same as for clayco-ordinating size of 225 112.5 7

for 10mm mortar joints. Generally, calcium silicatebricks are more accurate in form and size than redclay bricks, which inevitably distort in the manufac-turing process. The dimensional tolerances for calcium

darn ea mthee mess

ATES)

pprourinullyt exof

natuurindardbrirust

d bogieavements, alsos in clay blocks,

as sandlime orcommercially

e UK in 1905.common brickdurability for

nto mix designufacturing pro-nof a full rangetractive facings.ely priced and

t.

ricks is 215bricks, with a

5mm, allowing

silicate bricks dened in the stan2: 2003) are generally 2mm oexcept for thin-layer mortar when1mm tolerance is permitted ontolerances are usually less than onular and bricks of Imperial thicknorder.

MANUFACTURE OF CALCIUM SILIC(SANDLIME AND FLINTLIME BRICK

The rawmaterials are silica sand (ahydrated lime, crushed int, colowater. (If quicklime is used, it is fthe bricks are pressed, to preventhe steam treatment.) A mixturewater is used to manufacture thelime brick. The addition of colocrushed-int aggregate to the stanthe application of texturing to thethe full product range of smooth,nishes.

The appropriately proportioneinto brick units, stacked on bd (BS EN 771-ach dimension,aximum of onlyheight. Actual

illimetre. Mod-can be made to

BRICKS

ximately 90%),g pigments andhydrated beforepansion undersand, lime andral white sand-g pigments orcomponents orck surface givesic and textured

lend is presseds, moved into


Fig. 1.26 Manufacture of calcium silicate bricks

the autoclave and subjected to steam pressure (0.81.3MPa) for 4 to 15 hours at 180C (Fig. 1.26). Thiscauses the hydrated lime to react chemically with thesurface of the sand particles, enveloping them withhydrated calcium silicates which ll mspaces between the sand particles. Sucalcium silicates react slowly with carbothe atmosphere to produce calcium cagradual increase in the strength of the

APPEARANCE

The manufacturing process results inand dimensions, and with the untesilicate bricks, a smooth nish. Theextensive, from white and pastel shadeep reds, blues, browns, greens anvisual effect on the brickwork tends tosion. The bricks tend to bemore brittleand are therefore more susceptible to darrises.

SPECIFICATION OF CALCIUM SILICATE

Types

Both solid and frogged calcium silicateable. Manufacturers produce a wide ra

specials to BS 4729: 2005; special specials to clientsrequirements and brick slips for facing reinforcedconcrete.

od ftedlnt cs. Teforr, cae ththe

ate-rbri

ter

2: 2lasseuch of the voidbsequently then dioxide fromrbonate, with abricks.

accurate shapesxtured calciumcolour range isdes through tod yellows. Thebe that of preci-than clay bricksamage on their

BRICKS

bricks are avail-nge of matching

Durability

Calcium silicate bricks have gobut should not be exposed repeasolutions, acids or industrial efuenesium or ammonium sulphatea negligible salt content and therand sulphate attack on the mortawithin the bricks. The bricks artant to sulphate attack and canbelowgroundwith a suitable sulphmortar. However, calcium silicatebe used as pavers where winexpected.

PHYSICAL PROPERTIES

Compressive strength

The British Standard BS EN 771-range of compressive strength cTable 1.8.rost resistance,y to strong saltontaining mag-he bricks havee eforescence,nnot arise fromemselves resis-refore be usedesisting cementcks should notsalting can be

003 denes thes, as shown in


Table 1.8 Minimum compressive strength for calcium silicate bricks

Compressive strength class Normalised compressive strength (MPa)

5 5.07.5 7.510 10.015 15.020 20.025 25.030 30.035 35.040 40.045 45.050 50.060 60.075 75.0

Weight

Most standard calcium silicate bricks weigh between2.4 and 3.0 kg, but densities can range from below 500to above 2200 kg/m3.

Water absorption

Water absorption is usually in the range 815% byweight.

Moisture and thermal movement

Unlike clay bricks, which expand aftersilicate bricks contract. This shrinkagthe bricks become wet before use; thetection of brick stacks from saturatiSimilarly, unnished brickwork shoufrom both saturation and freezing dution. Reversible moisture movementcalcium silicate bricks than for clay bsion joints must be provided at int7.5 and 9.0m. Such movement jointsbridged by rigid materials. Generallymix should be used (e.g. 1 : 2 : 9 cemenexcept below damp-proof course levelcopings, to prevent visible cracking of eor the bricks.

Typical reversible moisture movemeTypical reversible thermal movemenThermal movement = 814 106 d

Thermal conductivity

The thermal conductivities are equivalent to those ofclay bricks of similar densities.

The thermal conductivity of calcium silicatebrick ranges from 0.6W/mK (Class 20) to 1.3W/mK(Class 40).

Fire resistance

The re resistance of calcium silicate bricks is similarto that of clay bricks, with solid 100mm calcium sili-cate brickwork giving 120minutes and 200mm giving360minutes re resistance, according to BS 5628-3:2005. The standard illustrates only marginal differ-ences in re resistance between calcium silicate andclay bricks. Calcium silicate bricks (with less than 1%organic material) are designated Euroclass A1 withrespect to reaction to re.

Acoustic properties

Acoustic properties are related to mass and are there-fore the same as for clay bricks of equivalent density.

CALCIUM SILICATE BRICKWORK

Most design considerations are the sHoulare inrancproapprlemeffedimbricthe

ildin.27)rickporare rebusty ofernag thring, calciume is increased ifrefore, site pro-on is essential.ld be protectedring construc-is greater for

ricks, so expan-ervals betweenshould not bea weak mortart : lime : sand),(DPC) and forither themortar

nt =0.05%t =0.05%eg C1

clay or calcium silicate brick.silicate bricks are particularly popreecting properties, for examplatria. Their smooth crisp appeaabrasive surface is particularly apinterior nishes and also forms anpainted nishes. The use of compmortars enhances the aestheticstrongly coloured bricks. Theirracy gives some advantage in theand cost is comparable to that ofbricks.

The interior of the Queens Bufort University, Leicester (Fig. 1effective use of calcium silicate bing a light internal space. Incorivory Flemish-bond brickwork aof polychromatic features and roobtuse-angle quoins. The accuracemphasises the clarity of the inting the disciplines of engineerinhouses.ame for eitherwever, calciumfor their light-light wells or

e with a non-priate for someopriate base forentary colouredct when usingensional accu-klaying process,equivalent clay

g of De Mont-, illustrates thework in creat-ted within thestrained bandsarticulation ofthe brickwork

l form, reect-at the building


Fig. 1.27 Polychromatic calcium silicate brickwPhotographs: Lens-based mediaDe Montfort UnorkQueens Building, De Montfort University, Leicester. Architects: Shoriversityt Ford & Associates.

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