Masonry Construction Manual - The Building Of Masonry

Thebuildingof masonry

Thebuildingof masonry KonradZilch, Martin Schdtz

Thestandardof workmanship is a criticalfactor that determines the load-carrying capacityand serviceability of masonry, especially because, in contrastto reinforcedconcrete,timbe.ror steel,all the importantstructuraland building sciencetasksare in thiscasefulfilledby one singlebuildingmaterial. Therefore,DIN 1053part 1 includesa separate sectiondevotedto the buildingof masonry. The aim of this sectionis notonlyto guarantee thatthe aforementioned tasksare fulfilled,but alsothatthe appearanceand aestheticsof masonryconstructions complywithcertain standards, In addition, thesepracticalconsiderationsare intendedto resistthe undermining of qualitystandardsas a resultof the growing pressureon costsand time,as well as the declinein standardsof trainingevidenton site. Consequently, the parameters for carefulplanningand buildingof masonryensurethatthe practicalrealization is as freefromflawsas possible. In the end,rationalization measuressuch as buildingwith large-format units,withoutmortar or with kit-typeelementsand so on, can lead to moreeconomicmasonryonly if special reouirements are olacedon the standardof workmanshio of the wall.

Mixingand using mortar on site Mixingmortar lf mortaris to be mixedon site.the cement, admixturesand additivesmustbe storedin a dry placeprotectedfromthe weather.Aggregatesmustbe storedundercleanconditions so thatthey cannotbe contaminated by salts, loam,organicsubstancesor largestones. Gaugingthe quantitiesof mortaringredients mustbe carriedout usingscalesor suitable containers, e.g. bucketsor gaugeboxeswith volumetricgradations,but neverwith shovels, in orderto guaranteea consistentmortarmix. Forsmallamounts,mixingis carriedout manually in a tub with a sandshovelor - particularly withthin-bedmortars- with a mixingblade As a rule,however, attachedto an electric,drill. a suitablysizedelectrictilt or non-tiltdrum

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should Mixinginstructions mixeris employed. be attachedto the machinein a placewhere should they'areclearlyvisible.Therawmaterials be mixeduntitthemortarhasan evenconsistencythat is suitablefor the intendedjob. Premixedmortarsare becomingincreasingly popularas an aid to rationalization and for ensuringconstantmortarqualityin termsof workability, strengthetc. consistency, Accordingto theformof supply,we distinguish betweenpremixeddry modar,premixed"coarse stuff"and ready'mixedmortar(includingmultiOn site,onlythe required chambersilomortar). amountof waterneedsto be addedto presilomoftar, mixeddry moftaror multi-chamber or the requiredamountof waterplus cementto premixed"coarsestuff".No aggregates,additivesor admixturesmay be mixedintopremixedmoftars.Premixeddry mortarand premixed"coarsestuff"are preparedon site in a mixer,but ready-mixedmortaris delivered readyto use in a workableconsistency(see "Mortarsfor masonry"). Differenttypesand groupsof mortarsmay only be preparedand usedtogetheron site if miscan be ruledout.This is takesin identification particularly so in the caseof normalmortarsof mortargroupsll and lla becausethey lookvery similar. Mortarnormallycontainscementas the bindan alkalinereingagent,whichundergoes actionin the presenceof wateror moisture. Therefore,protectskinand eyes.Uponcontact withthe skin,rinsewithwater,uponcontact withlhe eyes,consulta doctorwithoutdelay.

Using mortar

Thetrowelis stillthe besttoolfor layingsmallmasonryunits.Thetrianand medium-format gulartrowelhas a favourablecentreof gravity wrist and puts lessstrainon the bricklayer's than.thesquaretrowel.The advantageof the latteris, however,that ii is easierto lay and spreadlargeramountsof mortarevenly. The magonryand moftarindustrieshavedevelopedthe so-calledmortarsledgefor econmasonry with large-format omic construction walls.This unitsas wellas for one-brick-thick

tool matchesthe widthof the walland is pulled alongthe bed joint,therebydepositinga constantamountof mortarontothe bed joint througha slit.Thismakesit possibleto applya bed jointof constantthicknessup to 1Om long acrossthe fullwidthof the wall in one operation. Thin-bedmortarsrequirethe useof toothed trowelsor mortarrollers,whichguaranteea consistentapplicationof the mortarjLlst1 mm thick.The masonryunitis frequentlymerely dippedin the mortarandthenlaid.A comparativelylargeamountof wateris extracted fromthe "green"mortarin the caseof high absorbencymasonryunits,whichmeansthat the hardeningprocessof the mortarmay not be completedbecausethis requiresa certainminimumamountof water.The mortar driesout and the resultis pooradhesion betweenmasonryunitand mortar.Thiscan be preventedby adequateprewettingof high absorbencymasonryunitsor by mixingan additiveintothe mortarto increasethe water of retentioncapacity.The recommendations the mortarsuppliershouldbe followedin the caseof premixedmortars. Anotheradvantageof prewettingor using additivesis that leachingof water-retention saltsfromthe cementin the water-soluble mortaris reducedor prevented.As the water on the saltscauseefflorescence evaporates, the surfaceof the masonryunitswhich, and therealthoughharmless,is unattractive fore mustbe removedby repeatedbrushing (see"Buildingand cleaningfacingmasonry"). As mortarhardensit loseswaterand so is subjectedto evermoresevereconditionsby the masonryunits.Therefore,everytype of pretreatment and subsequenttreatmentof the masonry,e.g. prewettingthe masonryunits, protectingthe newlybuiltmasonryagainstrain, strongsunlightand prematuredrying-outby or spraying coveringit withplasticsheeting, the new masonrywithwater,benefitsthe qualityof the mortarand hencethe masonry. true in the first3-4 daysafter This is particularly l a y i n g[ 1 6 4 ] .

and qualitytests Suitability

2.5.1 Arrangementof perpends

Masonryd>115mm

lvlasonryd>115mm

mm 'Tipped

Protecting masonry against moisture

and tailed"

Joint

Fullmortarfilling

on the masonryand to damage(e.9.spalling causedby the formationof saltcrystals)[54, 164,2141.

Joint

Mortarin grooveonly

No mortar,tongueand grooveconnection

Quality control of prescribed masonry (RM)

Suitabilityand qualitytestsare not requiredfor prescribedmasonrybecausethistype of masonryis basedon manyyearsof experience of stanof usinga "prescribed"combination The . dard masonryunitsand standardmortar.. Suitabilityand qualitytests buildingcontractormustcheckthatthe details of the on the deliveryslip or the packagingof masonAccordingto DIN 1053,the properties This mustbe verified. buildingmaterials ry unitsfor prescribedmasonrymatchthoseon Mortar requirement is fulfilledby suitability and quality the buildingauthoritydocumentation. mixedon sitefor prescribedmasonryrnustbe tests.The suitabilitytest stipulateswhetherthe against' duringconstruction checkedregularly typesand quantitiesof certainraw materials tableA.1 of DIN 1053part 1 (seeLable2.1,25) aresuitablefor the production of a building testto ensurethatthe mixmaterialwith definedproperties,e.g. strength, or usinga suitability Forpremixed grossdensityetc.Thistest is carriedout ing ratiois beingmaintained. mortars,the detailsof the type of mortarand beforethe actualproduction of the building mortargroupon the deliveryslip or packaging materialor the buildingof the masonry.The qualitytest is carriedout on randomsamples mustbe comparedwiththe technicaldocumentation, and the gradenumberand the of the buildingmaterialproducedfor useon withthe supplyingworkscomparedwiththe order. the buildingsiteand simultaneously Mortarsof groupllla mustundergoa comin orderto verifythatthe actualconstruction, pressivestrengthtest accordingto DIN 18555 intendedmaterialpropertieshavebeen part 3 carriedout on threeprismsfromthree achieved.The qualitycontrolof masonryunits differentmix batchesper storey,but at least is carriedout withinthe scopeof the manuevery10 m3of mortar,and be checkedagainst facturer'sown qualitycontrolmeasures,and of Dl-N1053parl 1 tableA.2. the requirements thoseof outsidecentres,at regularintervals. Buildings withmorethansixfullmasonry Layingduring cold weather The requirements for this are stipulatedin the storeysrequirea qualitytestto be carriedout individual standards coveringthe different per storey,but at leastfor every20 msof morMasonrymay be builtduringfrostyconditions typesof masonryunits.The manufacturer's include tar, evenfor normalmortarsof groupsll, lla onlyif certainprotectivemeasuresare carried ownqualitycontrolduringproduction andthin-bed out.Theseincludecoveringthe aggregatefor constantmonitoringof the productionprocess and lll as wellas for lightweight mortars.Thistakesaecount.ofthe higher the mortarwith insulatingblanketsfor the temto guaranteethatthe masonryunitsproduced placedon the load-carrying peraturerangefromOto +5'C; coveringthe complywiththe criticalteohnicalparameters. requirements capacityof such masonryand henceon the masonry unitswaitingto be laidwithinsulating Monitoringby approvedoutsidecentrestakes quality requiredconsistencyof the mortarproperties blanketsfor the temperaturerangefrom-5 to the formof checkingthe manufacturer's in the lowerstoreys.As the increasedrequire0"C;heatingthe mixingwaterand the aggreduringproduction and en. controlmeasures gateandworkingin tentsor protectiveshelters. suringthatthe personnel used mentsdo not applyto the top threestoreys, and equipment for those this extraqualitytest is unnecessary As the temperaturedropsstillfufther,develop- meetthe requiredstandards. mentof the mortarstrengthslowsdownand In the caseof mortars,a suitabilitytest accord- sroreys, practicallycomesto a haltat about-10'C. ingto DIN1053part1 appendixA.5 is necesWheneveipossible,masonryshouldnot be saryonly if the serviceability of the aggregate builtat such lowtemperatures. hasto be verifiedor if admixturesand addiQuality control of masonry according to suitability test (EM) Frozenbuildingmaterialsmay not be usedat tivesare to be used. '1053part2 testsaccordingto DIN Suitability anytemperature. Furthermore, newlybuilt Furthermore, the suitability test needsto be premixed the strength classof preliminary to establish are required masonry, testfor delicateelements and columnsin carriedout as a test.This particular, masonryaccordingto suitability andthin-bed shouldbe protectedagainstfrost mortars,includinglightweight involvesallocati;rgthe masonryto a strength and precipitation modarsonlyfor structureswith morethansix by a coveringof insulating classby way of a compressivestrengthtest blankets.If suchmeasuresare not carriedout, fullmasonrystoreys(see2.1.28). no furthermasonryunitsmay be laid on The buildingcontractoris responsiblefor carcarriedout on test samplesaccordingto DIN issueof a 18554part1 and the subsequent masonryalreadyfrozen.Sectionsof masonry ryingout on-sitequalitytestsfor mortarwithin Thismustbe provided certificate. the qua- classification damagedby frostmustbe removedbefore the scopeof checkingand assessing conworkcontinues,On no accountuse antifreeze lityof prescribedmasonry(RM)or masonry to the buildingsitepriorto commencing structionworkwithsuch masonry.The suitabilagentsor de-icingsaltsbecausethis can lead test (EM). accordingto suitability (e.9.saltdeposits)appearing itytest mustbe carriedout by an approved to efflorescence

Masonry unitsareusuallydelivered wrappedin plasticsheetingon palletsand henceare protectedagainstsaturationup to the time of laying.As saturatedmasonryunitsdo not develop adequateadhesionto the mortarand,furthermore,increasethe energyrequiredfor drying outthe primarystructure,bricksand blocks awaitlnglaying,as well as the unprotected toosand sidesof individual elements suchas walls,spandrelpanelsand openings,mustbe protectedagainstprolongedrainfallby means of tarpaulins or plasticsheeting. Theseshould. be securedagainstupliftby way of battens naileddownor by heavymaterials.In addition, temporarydrainagemeasuresshouldbe taken beneathroofguttersif the rainwaterdownpipes havenotyet beenconnectedin orderto preventlocalsaturationof the masonry.Following theserecommendations will ensurethatthere is no damageto the masonryin the formof, for example,shrinkagecracks,efflorescence or reducedstrength[175].

Thebuildingof masonry

respectto buildingscienceproperties andthe resistance of anyrendering to drivingrainand cracking. Moftarshouldalwaysbe appliedoverthe full bed jointbecausethisjointhas an important structuralfunctionfor the loadbearingbehaviourof masonry,i.e.the uniformtransferof vertical comoressivestressesas well as tensile and shearstressesby way of adhesionand friction. Voidsin the bed jointsand varyingjoint thicknessesleadto stressconcentrations whichin turnreducethe load-carrying capacity and increase the riskof cracking. Thethickness of the bed jointinfluences the transverse tensilestressin the masonryunits throughthe lateralstrainbehaviour and is thereforepartlyresponsible for the compressivestrengthof the masonry.Therefore, thick 2.5.2 Buttjoinl bed jointsare structurally lessfavourable,but on the otherhanda minimum thicknessis necessaryto compensatefor the (permissible) materialstestinglaboratory.lt mustbe repeat- deviations in the sizesof the masonryunitsand ed if masonryunitswith a differentarrangeto allowfor practicalbuildingconsiderations. mentof perforations areto be usedfor the Thethickness of the bed jointis about12 mm masonryor if changesto the combinationof for normaland lightweightmortars,between5 raw materialsor the methodof productionof and 7 mm for medium-bedmortars,and the masonryunitscouldinfluence the strength between1 and 3 mm for thin-bedmonarsin of the masonry.Masonryaccordingto suitabili- conjunctionwith gaugedbrickwork. ty test does not needto undergoa qualitytest. The peroendsaremuchlessrelevant thanthe ln orderto checkthe rawmaterials on site, bed jointsin termsof structuralfunction everydeliveryof masonryunitsmustincludea becausethey do not helpto accommodate document whichincludesdetailsof the DIN tensileand shearstresses.Therefore,it is perdesignation of the masonryunit,EM designamissible to eitherfillperpendscompletely with tion,compressive strength(classification cermortar,only parilywith mortar("tippedand tificate),type of mortarand mortargroup, tailed"),or leavethemwithoutany mortar.Howmasonrystrengthclass,classification cer.tifiever,it shouldbe notedthat resistanceto catenumberand testingcentre.The delivery crackingdecreasesnoticeablywhenthe perslipor packagingis to be checkedto ensure pendsare onlyfilledpartlywith moftaror left that it matchesthe technicaldocumentation. withoutmonarbecausethe masonryunitscan Mortarmixedon siteshouldbe checkedat no longersuppofteachotheras is the case regularintervalsduringconstruction to ensure whenthe perpendsarecompletely filledwith that it continuesto complywiththe mixingratio mortar(seefig.2.5.1). on the classification certificate.In the caseof premixedmortars,the detailson the delivery slip regardingtype of mortarand mortargroup, Laying with mortar to the perpends the supplying worksand the gradenumber It is necessaryto providemortarin the permustbe checkedto ensurethey complywith pendswhenbuildingreinforced masonry, the detailson the classification ceftificate.As single-leaf unplastered masonry whichhasto withthe qualitycontrolof prescribedmasonry, be sealedagainstwindand drivingrain,ln the the compressive strengthof the mortarmustbe comoression zoneaboveshallowlintelsand in determined accordingto DIN18555parl3 and externalbasement walls(butdependingon the comparedwiththe requirements of DIN1053 loadbearing system).The perpendsareclassed part1 tablesA.2,A.3 and A.4.Thesequality as fullyfilledwith mortarwhenat leasthalfthe controlmeasuresmustbe carriedout for every wallthicknessis providedwith mortar. 10 m3of mortar,but at leastfor everystorey. The arrangement of mortarto the perpendsdependson thetypeof masonryunitsused.A full moftarfillingto the perpendis principally carPerpendsand bed joints ried outwith small-and medium-format masonry units.Thethickness of the perpendsshould The principaltasksof the jointsin masonryare be 10 mm for normaland lightweightmortars, to ensurethatihe masonryunitsare uniformly and 1-3mm for thin-bedmortars. loadedand to guaranteethe transferof forces Masonryunitswith mortargroovesin theirend fromunitto unit.Furthermore, they compensate faceseitherhavemortaraooliedto the faces forthe (permissible) deviations in the sizesof eitherside of the grooveto producevisible the masonryunitsand play a majorrolewith perpendswiththicknesses to a corresponding

146

fullmortarfilling,or the unitsare laidbrickto brickand the groovesfilledlater.In the brickto-brickmethod,the unitsare laidas close of the end facestogetheras the unevenness - will allow. process due to the manufacturing Generally, the gap betweenthe unitsshould is notbe morethan5 mm.lf thisdimension exceeded, thenthejointsshouldbe filledwith mortaron bothsidesof the wall in orderto guaranteean evensubstratefor plaster.

Laying without mortar to the perpends

Theperpendwithoutmortaris gainingin popularitybecauseit speedsup construction and requireslessmortar.However,certainmeasuresmustbe takento ensurethatthe reouirementsto be met by the componentregarding protection againstdrivingrain(e.9.rendering, (e.9.adequate thermalinsulation cladding); wallthickness,additionallayersof thermal (weightperm2by insulation); soundinsulation way of heavymasonryunits);and fire protecMasonrywithoutmortion are stillmaintained. tar to the perpendsis constructedeitherwith togetheror by the brickssimplybutt-jointed tongue usingmasonryunitswithan integral and groovesystem.Thislayingtechnique withoptimum achievesa masonryconstruction homogeneity. Peroends widerthan5 mm mustbe filledwith modaron bothsidesof the wall in orderto guaranteean evensubstratefor plaster.In termsof the structuralanalysisof masonry withoutmortarto the perpends,it shouldbe notedthatwhenanalysingshearthe permissiblereducedadhesiveshearstrengthooHS mustbe halvedand that in the caseof basementwallsthe earthpressuremay onlybe in the verticaldirection. carrieduniaxially

Junctionswith intersectingwalls Duringconstruction, the contractormustmake surethat immovablesupportsfor a wall (supportedon two,threeor foursides)as assumed in the structuralanalysisare actuallyrealized on site.An immovablesupportto a shearwall, whenthe supfor example,is onlyguaranteed podingwall and the shearwall are bothconequal structedof materialswith approximately the connection deformationbehaviour, betweenthe wallscan resisttensionand com' pression,and whenseparationof the wallsas is not deformation a resultof severedifferential expected(see"Lateralrestraintto walls"). A tension-and compression-resistant connectioncan be achievedby buildingbothwalls simultaneously andfullybondedtogetherbut alsovia a buttjoint.

walls Junctionswithintersecting

Bonded iunctions

A fullybondedjunction- alsovalidas such - is guaranteedwith rackduringconstruction ingor toothedarrangements onlywhereihe lengthof the returnis at leastone fifththe heightof thewall(seefig.2.5.3). Bothtypesof junctionconsumevaluablespace on the buildingsiteand this is oftennot desirabledue to operationalreasons,e.g.for easier erectionof scaffolds,to maintainunobstructed accessroutesetc. Therefore, to aid buildingoperationsthe structoothingor reversetoothing turallyequivalent maybe used(seefig.2.5.3).In thistypeof bondedjunction, thewallsarenot builtsimultaneously- supportand bracingto the wall are achievedat a laterdate.The tension-and connectionis created compression-resistant throughthe transferof compressionvia the masonrybond and tensionwiththe aid of reinforcement. Thisshouldbe builtintothe bed jointswith sufficientembedmentlengthand protectedagainstcorrosion.lf tensileforcesdo notneedto be transferred, thesetwo formsof bondedjunctionare onlyconsideredto comDression. accommodate

2.5,3 Arrangementof wall intersections

Wallto be supported

Butt-iointed junctions

Thebuttjointtechnique enablesthejunctions In thismethodthewallsare to be simplified. withouttakingaccountof the bondbutt-jointed they may be offsetlating rules.Consequenily, erally (see'fig. 2.5.2).A tension-resistant connectionis achievedby anchors(forwhicha structural analysisis required)placedin the bedjoints.lf the wallsare not builtsimultaneously,thenthe anchorsare leftprojectingand bentasideuntilrequiredin orderto prevent (seefig.2.5.q. injuries Thebuttjointtechniquemay be usedonlyfor internalwalls;externalcornersshouldalways be formedas fullybondedjunctions.Buttjoints arefullyfilledwithmortarin everycourseto ensureadequatetransferof compressionand continuity of the acousticinsulationproperties of thewall.Theanchorsareto be designed according to DIN1045section19.8.3in sucha waythat 1/100of the verticalloadof the loadbearingwall can be transferredat eachof the third-points of the wall height.Undersuch conditions,the supportedwall can be analysedas beingsupported on threeor foursides.The anchorsmay be distributedoverthe heightof the storeyto avoidan accumulation at thirdpoints,e.g.in all or alternate bed joints. It is recommended thatwallssuppoftedon only walls twosidesbe connectedto intersecting withnon-structural anchors. Inthe structuralanalysisof the walls,only recmay tangularand notcompoundcross-sections be useddesoitethe inclusion of anchors. Thebestanchorshaveprovedto be perforated flat barsof stalnlesssteelmeasuring300 x 22 x 0.75mm or pairsof V4Asteelwireties (as usedfor twin-leafwalls).

2.5.4 Butt-jointedjunctionwith varioustypes of anchors

Perforatedflat bar Masonryanchor Mild steelto DIN 488 Wiretie

147

Thebuildingof masonry

2.5.5 Chasesand recessespermissiblein loadbearingwallswithoutstructuralanalysis(dimensionsin mm)

Wall thickness

Horizontaland inclinedchasesrr

Vertical chases and recesses cut subsequently

Length of chase unlimited

Depthat ]<1.25mlong?t I Depth

I Width of single chases'

Verticalchasesand recessesbuilt in masonrybond

I Distance of i chasesand I recessesfrom

Min. distance of chasesand recessesfrom

Min. spacing of chasesand recesses

> 1.15 > 175 >240 > 300 > 365

> 115 >2xwidthof > width of ^L^^^ >115 chase > 115 or >24O > 115 > 115 chasesare permissibleonly in an area < 0.4 m above or belowthe structural on one side of a wall.They are not permissiblein horizontallyperforatedclay bricks. 2)Min. distancefrom openingsin longitudinaldirection> 490 mm, from next horizontalchase 2 x lengthof chase, 3)The depth may be increasedby 10 mm when usingtoolswherethe depth can be accuratelymaintained,e.g. masonrymillers,masonryslot saws,etc. When usingsuch tools, chases10 mm deep on both sides may be cut in walls> 240 mm thick. 4)Chasesthat extendmax. 1 m abovefloor levelmay be cut up to 80 mm deep and 120mm wide in walls> 240 mm thick. 5)The totalwidth of chasesaccordingto column5 and column7 pet 2 m of wall lengthmay not exceedthe dimensiongiven in column7. Forwalls lessthan 2 m long,the valuesin column7 shouldbe reduced in proportionto the lenqthof the wall.

The useof the buttjointtechniquehas several importantadvantagesfor on-siteoperations and the laterbehaviourof the walls:

the masonry.At the very least,the arrangement of chasesand recessesshouldbe checkedfor priorto construction. theirstructuralimplications Plannedchasesand recessesformedwithin 'The wallscan be builtseparately without the masonrybond,or providedin the formof inconvenient toothingin oneoperation. The channelblocks,or serviceductor pre-chased omissionof toothingspeedsup operations units(see"Specialformats,specialunits"), quiteconsiderably. In addition, theflushwall shouldbe takenintoaccounton the working surfacesand avoidanceof shortreturns drawings.As a rule,theseare moreaccurate easesthe erectionand movementof working and lesstime-consuming and costlythanchasplatformsand scaffolds. es cut subsequently. Whencuttingchases,it ' Theflushwall connectionmeansthatfewer mustbe ensuredthatthe intendeddimensions make-upunitsare requiredand thereare no are not exceeded.Chasesand recessescan bondingproblemsat intersections. considerablylowerthe load-carrying capacity 'The two intersecting wallscan be builtwith of a wall becausebesidesreducingthe crossdifferentcourseheightswithoutbonding sectiontheyalsodecrease,in particular,the problems, i.e.its is easyto combinewallsof bendingstrengthof the walland alterthe unitswith differentheightsand formats(but eccentricityin the remainderof the wall. stillcomplyingwiththe "octametric" system). Verticalchasesin wallsspanningin onedirec. The buttjointtechniqueavoidsthe creationof tion onlyreducethe cross-sectional area;their thermalbridgesat junctionsbetweeninternal influenceon the load-carrying capacityof the wallswithhighbulkdensityand external walls wallis henceof onlyminorlmportance. On the witha lowerbulk density. otherhand,verticalchasesin wallsspanningin ' The use of differenttypesof masonryunitsin two directions,whoseincreasein load-carrying the two wallsmeansthatthe effectsof longcapacityis due to lateralrestraintand henceis termdeformations are lesscriticalbecause relianton horizontal bendingmoments, can the anchorspreservea certainverticaldefor- havea severeeffecton the horizontalsoan. mationcapabilitywhileat the sametime proTherefore, theirinfluenceis takenintoaccount vidinga tension-and compression-resistant whendetermining whethera wall is supported connection betweenthewalls171,211,2141. on threeor foursidesby usingonlythe residualwallthicknessin the designof the section adjacentto a verticalchase,or by assumingan Chases and recesses unsupported edgeat thisposition. We also assumean unsupported edge if the residual Chasesand recessesare requiredfor all types wallthicknessis lessthan halfthe totalwall of buildingservices, e.g.heating, waterand thickness or < 115 mm. wastewaterpipes,electriccables,ventilation Horizontal chasesshouldbe avoidedif oossiducts.Owingto theirsignificance for the stabil- ble becausetheyreducethe cross-sectional ity of a wall,drawingsshowingthe sizesand area,and hencethe bendingstrength, along positionsof chasesand recessesshouldbe theirfulllength.At the sametime,theyhavean providedat an earlystageso thatthey can be unfavourable effecton the eccentricitvin the takenintoaccountin the structuralanalvsisof restof the wall.

148 I ! L

To simplifystructuralanalysis,DIN 1053part 1 for table10 specifies maximumdimensions are chasesand recesses.lf thesedimensions not exceeded,the effectof suchchasesand recesseson the load-carrying capacityof a wallis so minorthattheycan be ignoredwhen designing the masonry(seetable2.5.5andfig. 2.5.6).In addition,an analysisis notnecessary for verticalchasesand recessesifthe reduc- per m of wall length tion in the cross-section - is no morethan6% and the wall is not assumedto be supportedon threeor four wallthickness sides.In thiscase,a residual accordingto DIN1053part1 table10 column 8 and a minimumspacingaccordingto column (seetable2.5.5).lf the 9 mustbe maintained dimensionsof the chasesand recessesdiffer fromthe valuesgivenin the tablesor fromthe for verticalchases,they extrarequirement mustbe takenintoaccountin the designof the masonry.As the requirements of table 10 appearvery complicatedfor the practically in fig. mindeddespitethe graphicpresentation 2.5.6,thefollowing recommendations should be adheredto duringconstruction: ' Chasesand recessesshouldbe positioned well clearof heavilyloadedsectionsof masonry, opene.g.bearingsbeneathlintels, in piers ings.Theyshouldnotbe positioned and chimneyjambs. . The deothof a chaseor recessshouldbe as max.30 mm,in ordernot smallas possible, morethannecto weakenthe cross-section essary, . Horizontalchasesshouldonlybe positioned immediately belowfloor/roofsoffitsor immediatelyabovefloorlevelbecausein these zonessuch chaseshavevery littleinfluence on the loadbearingbehaviourof the wall (stabilityagainstbuckling). . Walls< 175mm thickshouldnot be chasedif at all possible.

facingmasonry Buildingandcleaning

permissible

in 2.5.6 Diagramof chasesand recesses facingmasonryis thatthe unitsshouldbe laid loadbearingwallswithoutstructuralanalysis and workedin a way appropriateto the mate(dimensionsin mm) rial.The differentsuctionratesof differentmaterialsmustbe takenintoaccount.Absorbent. Chaseof unlimited Depth of length chase unitsmustbe prewettedbeforelayingso that they do not extracttoo muchmixingwater fromthe mortar.The maximumratefor this is O Prewettingis not necessaryat 1.5kg/m2lmin. lowersuctionrates.lf prewettingis not carried cracksbetween shrinkage outwhenrequired, vo unitsand mortaror dehydratedadhesion zonesin the mortarcanformand helpdriving Buildingand cleaningfacing masonry -E rainto penetratethe facingmasonry.Less i_c absorbentmasonryunits,however,mustbe Certainruleshaveto be followedwhen planthe plasticity laiddry. In somecircumstances ningand constructing facingmasonryand of the mortarmustbe reducedin orderto prefacedwallsin orderto guaranteethe appearventsuch unitsfrom "floating"on the mortar of the ance,serviceability and durability due to theirlow suctionrate. masonry.Thisis especiallythe casefor exterO Edgeorstance nalwallsof facingmasonrywhicharefrequent- Completejointswithoutvoidsare producedby APZ-, o Lengln oT cnase ly exposedto drivingrain.In particular, the risk applyingthe mortarto the end of the masonry of saturation due to inadequateworkmanship unitand thenpressingit againstits neighbour, therebysqueezingout surplusmortar.Wall or thewrongchoiceof materialis frequently ffiquently jointsremainopenat firstand arefilledwith The damagecausedto the underestimated. grout course of completion of each facingmasonryis oftenextensiveand necessiupon m a s o n r [y1 6 2 ] . tatesmajorrepairs. Freshjointsmustbe curedfor at least3-5 days (see"Mixingand usingmortaron site"). Pleasereferto "Jointing"belowfor further Construction principles detailsof joints. Facingmasonryandfacedwallsshouldonly scaffold,because be builtfromfree-standing > 490 mm, from next horizontalchase 2 x length of ' putlogor otherscaffoldfixingholesare difficult cnase, Cleaning facing masonry to makegood subsequently. Thetop courseof 3)The depth may be increasedby 10 mm Whenusing we must disFirst for effective cleaning of all, masonry shouldbe coveredduringlonger toolswherethe depth can be accuratelymaintained, e,g. masonrymillers,slot saws etc. When usingsuch typesof soiling. tinguishbetweenthe different interruptions in the workand duringrain.lf tools,chases10 mm deep on both sides may be cut in possible, The mostfrequenttype of soiling,but the easimasonryunitsshouldnotbe laidin walls> 240 mm thick. therain,and in coldweathershouldnot be laid estto remove,is that causedby mortarand (see"LayingdurSecond,efflorescementduringconstruction. belowcertaintemperatures cenceand limestainingcan occuruponcomingduringcoldweather") pletionof the facingmasonry.Finally;atmosFacingmasonrymustbe builtvery carefully phericpollution of can spoilthe appearance e.g. becauseevenverysmallirregularities, perpendsaboveand belowa facingmasonryovertime. misaligned header,are disagreeable to the observer- and Thesoilingof facingmasonryduringconstruction is mosteasilydealtwith by removingmorit is oftenviewedfromcloseouarters.Perpendsor headers, tar droppingsand cementsplashesimmediwhichaccordingto the mustbe atelyas theworkproceedsor whenbuilding bondshouldbe alignedveftically, Opening E plumbed,becausedeviations of justa few mil- the nextsection.Water,brushesand sponges limetres discrepareadequatefor suchcleaning. can add up to considerable 6+ -lL> For d > 240: in of soilingis alsoimportant Theavoidance anciesoverthefullheightof thewall.All the dO L depth of chase< 80 facingmasonryunitsrequiredfor a certainsec- this context:adequateclearancebetween 66 | width of chase< 120 tionof the construction shouldbe orderedfrom tubs of mortarand facade,newlybuiltmasonry - t s 1 :o I coveredwith plasticsheetingto protectagainst ; B I onesupplierand intermixedbetweenseveral uJ6I oalletsin orderto avoidcolourvariationsin the mortardroppingsand cementsplashesor tts 4' \+- -l+ 4dge distance> finishedwork.lf necessary,a referencepanel againstsplashesof concreteand plaster. Widthof chase oftenoccurswhenlargerquantiEfflorescence for assessingmaterial(consistency of colour bond,jointingetc. ties of water(e.9.mixingwaterfromthe mortar, and dimensional accuracy), poorlydesigned/built eavesdetails,leaking Verticalchasesand recessescut subsequently shouldbe producedon site. Facingmasonryunitsmustbe carefullytranscopingsetc.)penetratethe masonryand wash portedand stackedon pallets,in packagingor out efflorescent e.g.calcium substances, sulphate, sodiumand magnesium in containers in orderto avoiddamagingcorners hydroxide, > 115 chloridesand nitrates,fromthe mortarand and edges.Furthermore, they are to be pro> 115 > 115 masonryunits.The absorbencyof the units tectedagainstthe weather,soilingand mech> 115 allowsthe dissolvedsubstancesto be transanicaldamage.Damagedunitsshouldbe > 115 ported where they are depoto the surface, rejectedor used in sucha way thatthe dammax. 1 m abovefloor levelmay be sitedat a pointwherethe watercan readily agedsectionis notvisiblein thefinishedwall. cut up to 80 mm deep and 120 mm wide in walls > 240 mm thick. for buildingdurable evaporate,e.g. at projectingpiersand at the Oneimportant condition

. As chasesand recessesare detrimental to the acousticand thermalinsulationproperties of a wallas well as its loadbearingbehaviour, "falsewall"installations are to be preferred possible,i.e.all servicesare wherever installedon the face of the wall or in service shafts.Duringthe interiorworks,the services are concealedbehindmasonrvor someother formof cladding.

2c

lL1zP

149

Thebuildingof masonry

2.5.7 Formingflushand "buckethandle" joints

2mm

cornersof buildings, wherehigherwind speeosoccur. Efflorescence, whichoccursduringconstruction by the dissolvingof efflorescent substances in the mortar(calciumcarbonate),can be avoidedby prewettingand hencereducing the absorbencyof the masonryunits.Most efflorescence disappearsaftera relatively shortperiodof exposureto the weather.Otherwise,the mosteffectivemethodfor removalis cleaningthe masonrydry with spatulas,suitable smallwoodenboardsand bristlebrushes. Sandblasting may be employedin certain cases,althoughthis may placeseverestresses on the facingmasonry;or cleaningwet with a cleaningagent.In this casethe masonrymust be prewettedstartingat the bottombeforethe cleaningagentis appliedin concentrated or dilutedform in accordancewiththe manufacturer'sinstructions. Thesemethodsare often employedfor old limestainingand leachingof, for example,calciumcarbonate.Veryeffective cleaningagentsfor clay brickworkhave provedto be thosebasedon hydrochloric, phosphoricor formicacid.The masonryshould be rinsedthoroughlywith wateraftercleaning to makesurethat all impuritiesare removed.lt alsopreventsthe masonryfromreabsorbing the solution againas it dries. Masonrysoiledby manyyearsof atmospheric pollution shouldonlybe cleanedby specialist contractors. lt is essentialto carryout a cleaningtestfirstin suchcasesto establishthe most suitablemethodof cleaning- so thatthe masonryremainscleanand does not suffer anysignificant damage. jets of cold and hotwater,jets of High-pressure waterwithadditives,compressed-air waterjets withadditives and chemicalcleaningprocesses involvingthe applicationof wettingagents, acidicor alkalicleanersand subsequent rinsing haveall provedto be suitablemethodsof cleaning.Whenchoosinga method,the effectivenessof safetyrequirements and disposalof the cleaningwatermustalso be.takeninto account[52, 175].One commonproblem thesedays is graffitismearedoverfacades.

Theycan generallybe removedby waterjets with additivesbut softersurfaceswill suffer underthistreatment.Specialgraffiticleaners basedon y-butyrolactone haveprovedto be a good alternative to mechanicalcleaning. productwitha Thisspecialplastic-dissolving pH valuebetween5.5and 6.0 is appliedto the facingmasonryand washedoff afterwardswith cold waterwithoutdamagingthe surface.

Jointing Jointingplaysa specialrolein facingmasonry and facedwalls:it sealsthe masonryagainst drivingrain,and lendsitthe desiredappearof the mortar,the set- . ance.The composition back,consistencyand positionof the jointsurfaces,and the way they are madeare crucial to the weather-tightness of facingmasonry to be effec- ' exposedto drivingrain.Therefore, joints tive, and finshouldbe water-repellent ishedflushwiththe surfaceof the masonrywheneverpossible.Thejointsforma fine lattice overthe wholesurfaceof the wall and so their aooearancehas a decisiveinfluenceon the characterand overallcolourof exposed masonry. Jointingcan be carriedoutduring construction, beforethe mortarhasfullyhardor later, ened(e.9.flush,"buckethandle"), afterrakingoutthejoints(pointing) [162,164].

Flush and "bucket handle" joints

The flushjointrequiresthe visiblejointsof the masonryto be filledcompletelywith mortar. Surplusmortaris trimmedoff withthe trowel. The "buckethandle"jointis formedafterthe , ' mortarhas startedto hardenby "ironingin"to a depthof 2 mm, compactingand smoothing with a sliverof wood,jointingironor pieceof plastichose(diameterapprox.1.5to 2 times must. thewidthof thejoint).Thesmoothing alwaysbe carriedout at exactlythe righttime and startingfromthe firstjointformedto ensure jointcolour(see2.5.7). a consistent The advantageof thesejointsis thattheyare ' afterbuildingthe carriedout immediately wellmasonryand so providehomogeneous, compactedjointsformed"fromone mould",so , to speak,throughouttheirdepth. However,thistype of jointingcan be carried out properlyonlywhenbed jointsand perpends are completelyfilledwith mortar,to avoidhav-' ing to makegoodwhensmoothingthe joints. Thispresupposes carefulbricklaying. The disadvantage, thatthe facingmasonry mustbe kept cleanduringconstruction

150

/

Jointdesign

2.5.8 Pointing

becausesubsequentcleaningof the facade couldleadto cementbeingwashedout of the joints,can be avoidedby usinga mortarwith goodcohesionand water-retention properties. Thispreventsthe mortarrunningdownthe face of the masonrywhen it inevitablysqueezesout of thejoints.

Pointing

Thisrequiresthe jointsof exposedsurfacesto be rakedout to deothof 15-20mm - but not as far as the firstrow of any perforations in the units- immediately afterconstructionby using a slightlytaperedstripof hardwood. Attempting to constructfacingmasonrywith the mortarleftbackfromthe edge to saverakingoutthe jointslateris not a properway of preparingthe outerjointsubstrate,and is thereforenot permitted.lt is alsoconsidered to rakeout the mortarVooorworkmanshio shaped.half-round or bevelledin the middleof a joint,becausethenthe pointingmortardoes notachievea properbondwiththe unitsand the mortarof the joints,and consequently does notprotectthe masonryagainstdrivingrain. Afterrakingout,any loosepiecesof mortar shouldbe removedfromthe facadesurfaces andthejointsby brushingand rinsingwith water,possiblywiththe additionof a cleaning agent.Priorto pointing, the facadeshouldbe saturatedwith water startingat the bottom.The pointingmortar(mixedby machineto a "plastic" consistency) is then pressedintothe jointsand wellcompactedin two operations,and excess mortarremoved, Inthe firstoperationthe perpendsare first compactedand thenthe bed joint;in the secondoperationthe bed jointsfirstand then theperpends(seefig.2.5.8). Suitablemeasures,e.g. sprayingwithwater, coveringwith plasticsheeting,shouldbe taken to protectthe freshpointingagainstpremature drying-out causedby draughts, sunshine etc. Thecomposition of the pointingmortarshould correspondmoreor lesswiththat of the mortar of the joints,and shouldbe preferablyof mor-

t a r g r o u pl l a ,l l l o r l l l a . The disadvantages of pointingarethat it encouragesthe productionof masonrywithout fullyfilledjoints,andthatjointingand pointing mortarswith differentmixes,or pointingmortar whichis too dry,leadsto diminished adhesion betweenpointingand moftaror masonryunit. Boththesedisadvantages weakenthe driving. rainresistanceof the facingmasonryand, as a result,impairthe durability of thewallconstruction.Therefore,pointingshouldbe usedonly whena particulareffect(e.9.colour)is desired, or whenthe surfaceof the masonrvunitis to a flushjoint. unsuited

Joint design The componentsof a buildingare subjectedto stressesand strainssuchas thosecausedby temperature, creepand shrinkagedeformacauses tions;Preventingsuch deformations restraintstresses,whichcan leadto cracks the appearingin the structure.Therefore, jointsas a designershouldineludemovement preventivemeasureto avoidcracking.Besides jointsmustcomdeformation, accommodating pensatefor manufacturing and assemblytolerances,and at the sametime complywith build(thermal and sound. ing sciencerequirements To do insulation, weatherand fire protection), this,theymustbe wideenoughand be filled' with suitablematerials. As jointsaffectthe appearanceof masonry, elethey shouldbe consideredas architectural However, theyshould mentsin the planning. be includedonlywhereabsolutelynecessary, and maintenance' becausetheirconstruction are costlyand involved.Jointsshouldbe straightand positionedlogically,otheruuise they becomecomplicatedand may not be fully effective.

Types of joints

Jointsare dividedintomovementjoints,rigid jointsand dummyjoints. and expanMovementjointsincludesettlement joints(e.9.between sionjoints.Settlement buildings)are calledfor whensignificantdifferentialsettlementis exoectedbetweentwo or moresectionsof a building.Theyextendover thefullheightof thebuildingand alsopass throughthe foundations.In such situationsit mustbe ensuredthatthe separatepartsof the threebuildingeachhavean independent dimensionalbracingsystem.The riskof differentialsettlementariseswhendifferentsections of the buildingimposedifferentgroundpresor sureson a subsoilsusceptibleto settlement whenthe type of subsoilchangesbeneaththe joints(e.9.verticaland building,Expansion jointsin facingwork)are requiredin horizontal

151

Thebuildingof masonry

2,5,9 Feasiblemovementjoint detail Wall expanded

',/,/,/ Wall contracted

,/././.

Roundclosed-cell /2strc/cotd Primer foradhesion

7//.

Compressed gaskel

<15mm Compressedgasket

as largecomponentsthat undergodeformation fluctuaa resultof shrinkageand temperature tions.As a rule,verticalexpansionjointscontinuedownas far as the too of the foundations. Thistype of deformation is lessdamagingto tendto foundations foundations and undivided Rigidjoints(e.9. compensatefor settlement. joints,joints assemblyjoints,construction betweenprefabricated elements)ariseas a resultof the.typeof construction or building operations.Suchjointscan alsoact as movementjoints,in whichcasetheyshouldbe formed and sealedas for suchjoints,Dummyjointsare producedonlyfor appearanceand haveno of functionsregardingthe accommodation deformations or tolerances,

The sealing of ioints

preformed sealinggasSealingcompounds, ketsand coverstripsare usedto sealjoints (seefig.2.5.9)[9]. Sealingcompounds elastic Here,the jointis sealedby permanently one-and twoand permanently elastoplastic partcompounds, silicone e.g.polysulphide, rubber,polyurethane or acrylicdispersions. elasticbut Thesematerialsare permanently of longdeformplastically underthe influence term loadingand hencereducestresseswithin in variouscolours thejoint.Theyareavailable and can be expectedto last15-20years.Sealing compounds mustbe appliedin dry conditionsat temperatures above+5"C.The masonry jointson bothsidesof the movementjoint shouldbe fullyfilledwithmortar,andthe opening for the jointitselfmustbe freefrom dust, mortardroppings, oil and greasein orderto achieveoptimumadhesionbetweensealing compoundand masonryand to avoidcracksin the longterm. A roundbackingstripof flexiblefoamedmaterial is insertedintothe openingbeforethe sealing compoundso as to be ableto injectthe compoundwith sufficientpressureand at the sametimegiveit a suitableform.Thissoof calledbackingcordmusthavea diameter about1.5timesthewidthof thejoint,mustbe withthe sealingcompoundand compatible mustnot absorbanywater.Afterinjectingthe or sealingcompoundusinga hand-operated gun,thejoint,isgenerally subcompressed-air givena slightlyconcaveprofile. sequently

Self-adhesive side

Cover strips

ffi \kp

&

ffi

ffi W

152

Preformedsealinggaskets sealing Jointsmay be filledwithpreformed gasketsmadefromopen-cellplastic.foam impregnatedwith a specialbitumenor polyacrylate.Therefore, the gasketsremainpermanentlyelastic,do not crackor becomebrittle, radiationand and are resistantto ultraviolet The preforrnedgasketis alkalinesolutions. squeezedtogetherbeforebeing inserted,and

alignedwiththe joint.As it attemptsto regain itsoriginalsizeand shape,it pressesagainst the sidesof the jointwith sufficientadhesionto In doingso,the gasketalso sealit immediately. of the sides for the unevenness comoensates of the joint.Preformedgasketscompressedto onethirdtheiroriginalsizeareadequateto createa dust-tightand airtightjoint;a gasket compressedto one fifthits originalsizecreates a watertightjoint. Cover strips A coverstripcan be clampedor gluedintothe jointto seal it, The contactpressureof cover stripsclampedintoplacemustbe adequateto preventthe stripdroppingout if the gap widensas a resultof, for example,a drop in temperature. The adhesionof the glueto the substrateis decisivefor gluedstrips.To improvethe adhesion,the sidesof the jointmay be carefully paintedor, in the caseof a highlyabsorbent material,sealedwith an epoxyresinsolution.' Drained joints Verticalmovementjointsin facingmasonrycan be designedas drained,i.e.open,jointsin buildingslocatedin regionswherelessdriving rain is to be expected,providedthe backing masonryand any insulationare permanently protectedagainstmoisture, e.g.an airspace, plasteror plasticsheeting.Suchjointsare ' restrictedto a maximumwidthof 15 mm and reouirean outerleafthicknessof at least90 mm.

The spacing and width of joints

the Thedesignof thejoints,i.e.establishing widthsof the jointsand the distancesbetween them,is carriedout by the structuralengineer the variables: and deoendson numerous structuralconceptof the respecttvestructure;' the dimensionsof the structure;the stiffnessof with respectto changesin the construction of stiffeningelements; length;the arrangement to the temperaturechanges;the insulation externalwalls;the shrinkageand creepbehaviourof the wallsand floors;the settlement i anticipatedetc. Outerleavesof masonryundergogreater changesin lengththaninnerleavesbecause they are subjectedto greatertemperature changes.Addedto thiswe havethe differential of the leavescausedby different deformation materialpropertiesand differentloadson the innerand outerleaves.The advicebelow shouldbe followedwhen designingmovement jointsin outerleavesof masonry: ' Verlicalmovementjointsare requiredat the cornersof buildingsand alsoin longwallsat a spacingof max.6.0 m for lightweightconcreteunits,max.8.0 m for calciumsilicate These units,and 1O-16m for claybrickwork.

Mechanical fixingsin masonry

differentfiguresdo not representdifferent standardsbut arethe resultof the different propertiesof thesefacingmaterdeformation ials.lf a facadeis takenaroundthe cornerof the buildingwithouta joint,the returnshould notbe longerthan5.0 m. In the caseof lintels overlargewindowand dooropenings,movementjointsarepositioned in linewiththewindow and doorrevealsaboveand belowthe openrngs. . Horizontal movementjointsare required beneathparapetsand roofoverhangs,below balconyfloorsand beams,belowjoistsand purlins, beneathwindowsandthresholds, and belowsupportsfor outerleaveswhen theyare morethan6.0 m highwith an outer leaf< 115 mm thick,and whentheyare more than12.0m highwithan outerleaf> 115 mm thick. Thewidthof the jointdependson the anticipateddeformation of the componentsand the deformability of the materialto be usedto seal thejoint.Thewidthis usuallyfiveto seven timesthe changein lengthto be accommodatedby the joint.Jointwidthsof 15-25mm arenormallychosenand the jointsspacedto suitthiswidth.Widerjointsare difficultto seal propeny.

of the trowelor rolleror sledgeshouldmatch the thicknessof the wall.Whenusinga trowel, thethin-bedmortaris onlyappliedto the bed jointtwo or threebricksaheadof the brick beinglaid,butwhenusinga rolleror sledge, rationalization measuresdictatethatthe mortar be appliedto thewholelengthof wall.The rollercan alsobe usedto placea glassfibre mat betweentwo layersof thin-bedmortar eachapprox.1 mm thick.Thehightearing resistanceof the rnatincreasesthe compressivestrengthof the masonryand the adhesive shearstrengthbetweengaugedbricksand mortar. Afterthe gaugedbrick is laid,the facesand edgesare alignedaccuratelybeforetappingit intoplacewitha rubberhammer. Anythin-bed mortarthat squeezesout is trimmedoff with a metalspatulaonce it hasstartedto harden.At the sametime,anyflaws,e.g.unfilledperpendsor bed jointsor damagededges,are madegood. Fromtimeto time,aftera brick is laid it should in orderto be removedagainimmediately checkwhethera completebed of mortaris beingachievedwiththe respectivemethodof application.

2.5.10 Examplesof plasticand injectionanchors coveredby buildingauthoritycertificates[15]

ilil

ww Plasticwall plugs

Mechanicalfixings in masonry Gaugedbrickwork

Verymanydifferenttypesof neighbouring constructions,componentsand fittingshaveto be Whenbuildingwithnormalor lightweight morfixedto masonryusinganchors,drivescrews tar,the differentpositionsand heightsof the and nails.Thesearesubjectedto tension, unitscan be compensated for to a cedain shear,inclinedtensionand compression, extentby adjustingthe thicknessesof the bed bending. joints.However,gaugedbrickworkand thinNeitherstandardsnorguidelines areavailable Therefore, loadbed mortar(withjointthicknessesof 1-3 mm) for assessing suchconnections. permitonlyminimaladjustmentof positionand bearingfixingsmay only use anchorscovered height.The resultof this is thatthe basecourse by a buitdingauthoritycertificate. mustbe laidwith extremecare becauseit also Othertypesof fixing(anchorsand nailswithout servesas the coursefor adjustingthe heightas certificates) may be usedfor minorapplicaplanari- tions.However,thesemay not be usedfor fixwellas the longitudinal andtransverse ry. lng constructions in the tensionzonesof roof Thebasecourseis laidon a bed of normalmo- and floorslabsand also notfor attachingcurrtarof grouplll andthenalignedhorizontally. tainwallfacadesand thermalinsulationcompositesystems[43,49,78, 109,110]. Small-and medium-format unitsor levelling units- 50-125mm hlghand up to 500mm long - areoftenused in the basecoursein conjunctionwiththe actualgaugedbricks. Anchors Oncethe basecoursehas hardened,the Anchorsarefixingsinsertedand securedinto gaugedbrickswiththeirassociatedthin-bed holesdrilledintosolidmaterials. Theirmain purposeis to permitthe attachmentof a whole mortarare used,startingfromthe second course.Thebed facesofthe gaugedbricks rangeof minoritemsbut they may also be shouldbe brushedbeforethe thin-bedmortar usedto anchorloadbearing components. is appliedin orderto ensurea clean,smooth Regardlessof the type of application,they bed face,whichhelpsto guaranteethe adheshouldalwaysbe properlyplannedand sized. sionbetweenunitand mortar.The thin-bed Anchorscan be classified accordingto various mortaris appliedto the bed jointeitherby dip- criteria. Onecommonmethodis to distinguish' pingthe gaugedbricksapprox. betweenthe type of anchoragein the drilled fric5 mm intothe mortaror by spreadingthe morhole- undercut, mechanical expansion, - and the materialof tar directlyontothe bed jointusinga special tion,grouting,a.dhesion trowel,rolleror mortarsledge,whichappliesa the anchor,Up to now,only plasticexpansion constantlayerof mortarto the joint.Thewidth anchorsand injectedgroutanchorshavebeen

lnjectionwall plugs

153

Thebuildingof masonry

2.5.11

Methodof functioning of anchors[13]

z Anchors for autoclavedaeratedconcrete Plasticexpansionand injectionanchorswitha cylindricaldrilledholeare not suitablefor autoclavedaeratedconcretebecausethis material lnjectionanchors are insertedintothe wall beforeofferingup the is verysoft,is damagedby the expansion forcesand alsocannotaccommodateany itemto be attachedand up to now haveonly special significantbondingforces.Therefore, beenapprovedfor fixingsin hollowmasonry anchorshavebeendevelopedfor fixingsin unrts. autoclavedaeratedconcrete.Theyare Theywork by way of the bond betweenthe anchoror anchorsleeveand the substrate.The anchoredby way of conicaldrilledundercuts due to virtuallywithoutany compression bond is achievedby way of an injectedgrout Plasticanchors cementor artificial expansion,or injection,or a special?rfoflge: basedon rapid-hardening can be usedfor fixingsin concreteas well as resin.However,injectionanchorsfittedin voids mentwhichallowslow expansionforcesto be transferred, thanksto a suitablesurfacedesign in masonryof solidand perforatedunits.They thetensionviathe mechanical alsotransfer are normallyinsertedthroughthe itemto be and partialcompactionof the autoclavedaerinterlockof the injectedgroutforcedintothe fixedand intothe wall.The anchorsconsistof ated concrete(seefig. 2.5.12).Thefixingof v o i d( s e ef i g .2 . 5 . 1 1 ) . a plasticsleeve,designednotto turnin the Whenusingrapid-hardening cement,the mor- componentssubjectedto heavyor dynamic hole,and an associated screwor nail.The tar is mixedwith a prescribedamountof water loadsmay requirethe useof boltspassed minimumdepthof anchorage throughthe aeratedconcretewall. is markedon beforebeingforcedintothe void by a handIn thiscasethewallis drilledrightthroughto the olasticsleeve.A collarat the outerend of operatedpump.The resultis thatthe void in thesleeveprevents the anchorbeingpushed the masonryis moreor lessfilled.Theamount matchthe diameterof the boltand a wider pocketformedon the rearface.The itemto be toofar intothe holeduringassembly. by using of mortarrequiredis minimized fixed is fittedoverthe bolt,whichpasses The geometryand lengthof the screwor nail mesh. by a polyamide anchorssurrounded throughthe wall and is securedon the rear are matchedto the internalgeometryand Injectionanchorsbasedon aftificialresinconface,and pressedup againstthe autoclaved lengthof the sleeveso thatthe anchoris prop- sistof a meshsleeveand a threadedbar with aeratedconcrete.Largewashersor anchor erlyexpandedoncethe screwor nailis in nut and centeringring,or a metalsleevewith place.However, olatesare fittedto the bolton bothsidesof the expandingplasticanchors internalthread,plusthe artificialresinmortar. withnailsmayonlybe usedfor fixingfacades The separatecomponents,resinand hardener, wallto distributethe load in concreteand solidmasonryunits. areforcedthrougha mixingtube and injected Plasticanchorsmay not be usedfor pureaxial - thoroughly mixed- intothe meshsleeve.The lnstallinganchors drilled; tension,butonlyfor inclinedtensionat an threadedbar or the sleevewith internalthread Anchorsrequirethe holeto be carefully pushedintothe meshsleeve. lackof carewhen drillingcan leadto an overangleof at least10'. In solidmaterials theten- is subsequently sionis transferredby friction.The expanded Anchoring thewallplugin theweb of a mason- sizehole,whichresultsin a rapiddecreasein partof the anchoris pressedagainstthe side ry unitrequires the drilledholeto be carefully the pull-outstrengthof the fixing.Holesfor air in anchorsin masonrycan be drilledwith a norof the drilledholeand henceactivatesthe friccleanedby brushingand compressed tion.In hollowmasonryunitsthetensionis also orderto guaranteean adequatebondto trans- mal rotarydrill,a percussiondrill (rotationplus action)or a hammerdrill rapidpercussion transferredby the interlockbetweenthe anchor fer thetension. approvedfor fixingsin masonry(seefig. 2.5.10). Thereare alsospecialanchorsfor fixingthermal insulation compositesystemsand for anchoringwalltiesfor twin-leafmasonryand facingmasonry.Theseanchorsystemsare in turn basedon the plasticexpansionanchors andthe injection anchors.Finally, thereare specialwall plugsfor autoclavedaeratedconcrete,whichpermitcomponentsto be attached to thisverysoftrnaterial.

1U

geometryand the shapeof the substrate(see f i g .2 . 5 . 1 1 ) .

measures Rationalization

(rotation plusslowerbut morepowerfulpercussionaction). Percussion and hammerdrillsmay be usedin solidunitswith a densemicrostructure,butoniyrotarydrillsmay be used in perforated,autoclavedaeratedconcreteand lowstrengthunitsso thatthe holeremainsthe propersizeand the webs and wallsof perforatedunitsare not damagedby the percussiveaction.lt is recommended to grind normal carbidedrills,whichare designedfor rotation pluspercussion action,sharpin the direction of rotation, similarto a steeldrill,to achieve progress optimum whendrillinga holepurely by rotation. Withfew exceptions, the holemustbe drilledat least10 mm deeperthanthe depthof anchorage.Thisleavesroomfor any dustor for the pointof the screwto protrudethroughthe end ofthewallplug,and henceguarantees the correctfunctioning of the anchor. ln solidcross-sections, dust resultingfromthe drilling shouldbe removedfromthe holeduringandafterdrillingin orderto avoiddiminishedfrictionand bond effects,and to guaranteethe load-carrying capacityof the anchor. Therearevariouswaysof fixingthe actual neighbouring construction, componentetc. Theholescan be drilled(afterhavingfirstused thefixingholesin the componentto establish thepositionsof the holesin the wall)and the anchorsinsertedbeforepositioning the componentagainstthe wall and screwingit into place.Inthiscasethe anchorusuallyfinishes flushwiththe surfaceof the wall and the diameterof the holein the wall is largerthanthat of the holein the component.Alternatively, the holesin thewallcan be drilledusingthefixing holesin the componentas a template(which guarantees accuracy)and the anchors inseded intothe wallthroughthe component.In this casethe diameterof the holein the comoonent is at leastas largeas that of the holein the wall.Thisprocedure is particularly suitable wheneachcomponentrequiresmorethantwo anchors andfor largenumbersof fixings.lt is alsopossibleto attacha componentat a certaindistancefromthe wall.A tension-and compression-resistant fixingis achievedby usingan injection anchorhavinga metricinternalthreadintowhicha screw,bolt or threadedbar with locknutsis fitted, Modesof failure of anchors Anchorscan fail as a resultof overloaded anchoragepoints,incorrectinstallation or the inadequate load-carrying capacityof the substrate.Plasticanchorscan fail by beingpulled outof the substrate,althoughthis does not seriously damage.A pull-outfailuremeansthat an excessive.load has overcomethe frictionor bondin the hole;a rupturedfixingmeansthat thestrengthof the screwmaterialwas not adequatefor the load. Fractureof the masonrymaterialitselfis the normalmodeof failurefor an iniectionanchor.

Thishaooenswhenthe tensionloadsare too high,the masonryis not strongenoughor the A wall can depthof anchorageis inadequate. fractureif it is not largeenoughto carrythe loadsor if the edgedistances or spacingsof fixingsare too smallfor the expansionforces introduced.

Nail anchors

Nailsand drivescrewsare employedonlyfor minorconstructions with low anchorageloads, and primarilyin aeratedconcretemasonry. Lightweightitems,e.g. battensfor wooden panelling, arefixedin placeby drivingthe nails or drivescrewsdirectlyintothe autoclaved aeratedconcrete. The best nailsfor this aretapered,galvanized squarenails60-180mm longwitha roughsurface finish.Theyshouldbe hammeredhome fromalternateangles.Othertypesof nails includetwistednailsand specialnailanchors and hammeredplugsfor autoclavedaerated concrete.Thetwistednailgainsits anchorage by way of frictionand expansion,the othertwo formsby way of a mechanicalinterlock(see fi9.2.5.13).

2,5.12 Examplesof anchorsfor autoclavedaerated concrete

Expansionwall plug with compaction

Wall plug expandswhen expanding shell is forced over cone.

Through{ixingfor particularlyheavyor dynamicloads

Rationalizationmeasures Building to save space and costs

Therisingcostof buildingmeansthatthe optimizationof costsand space in the housing important. marketis becomingincreasingly The potentialfor optimizingthe use of the availin exploitablespaceis to be foundprincipally ingthe optionsfor optimizing the loadbearing structureas containedin standardsand regulations.Theseootionsmustbe takeninto accountearlyin the planningstageof a building project. Onefundamental optimization optionfor the loadbearingstructureis the regulararrangementof shearwalls.A regulararrangement providesexcellent wall stability and minimizes thicknesses. In addition, the spansof thefloors can be madeequal,whichin turnminimizes slab depthsand the amountof reinforcement required. Anothermeasurefor savingmoneyand space is to reducethe thicknessesof loadbearing to wallsto the minimumdimension necessary satisfystructuraland buildingsciencerequirementsby employingthe moreaccuratemethod Accordingto DIN1053part1, the of analysis. minimumthicknessfor loadbearinginternal and externalwalls,as well as the loadbearing leafof twin-leafexternalwalls,is 115 mm. Howwallthickness ever,a minimum of 175mm is recommended for single-leafexternalwalls with a thermalinsulationsystemin orderto. complywiththermaland soundinsulation requirements. Internalpartitions> 115 mm may

2.5.13 Nail anchorsfor autoclavedaeratedconcrete , masonry

Squarenail

Twisted nail

Pr+

P,-,

P.-b,

Aerated concrete nailanchor

Aerated concrete hammeredplug

155

Thebuildingof masonry

2.5.14

-

/q

Workinghoursguidancefigures[h/m3]

Conventional masonry 2 D F/ 3 D F 4.60 h/m'

4.O 3.5

2.5 2.0 gauged elements 999 x 623 x 300 mm

be considered as loadbearing. Thegainin floorareawhen usingmasonrywallswiththese minimumthicknessesis aoprox.5-7o/o aomparedto the commonwallthicknesses of 240365 mm. In addition,fewermasonryunitsand thin lessmortarare required.Furthermore, masonryis moreflexibleand thereforeless liableto crackthanthickermasonry, in which the structuralstressesare lower.The use of a skimcoat insteadof 15-20mm "normalplaster" gainin floor can alsoachievean additional to approx.2% dependingon areaamounting the sizeof the room.However,masonrywalls ratioscall for the use of with largeslenderness masonryunitswith high strengthand high grossdensity,as well as high-quality mortar ( M Gl l l ,M G l l l a ,D M ) .T h ea c t u abl u i l d i n o gf masonryat an optimizedcost is lessa question of optimizingthe loadbearingstructurethana matterfor rationalized buildingoperations, the masonryunitsand special useof large-format construcbuildingmethods(e.9.prefabricated t i o n )[ 1 3 9 ,1 4 0 ] .

mortarfrom 50 l/m3for a thick joint to 5 l/msfor the applicationof a cona thinjoint.Moreover, stantbed of modarusinga modarsledgeor specialtrowel,and the resultinglayingof a row of masonryunits,achievesa time savingof up workin pairs,,one The bricklayers 1o25o/o. thethin-bedmortaralongthewall spreading withthe mortarsledgeor specialtrowel,and the otherlayingrowsof masonryunitsin the preparedmortarbed [75;. in masonryconstruction Furtherrationalization can be achievedby usingthevariousspecial unitsand specialcomponentsproducedby the masonryindustry(see"Specialformats,speis to Theaimhere,in padicular, cialunits"). integrateothermaterials- steeland concreterequiredfor structuralreasonsintoan essenmasonryconstruction, tiallyhomogeneous while reducingthe workrequiredto integrate suchmaterials.

The quantitiesof materialsand numberof working hours required but are subject can be determinedtheoretically practice.Organifluctuationin Rational laying techniques to considerable zationon the buildingsite is criticalfor this.To The aim of rationalbricklayingis to minimize it is the numberof unitsrequired, the numberof operationsto be carriedout by calculate important,for example,to knowwhetherthe whenbuildinga wall,and at the the bricklayer sametimeto adaptthe ergonomicsof the work unitswill be cut on sitewith a hammeror witha to meetthe needsof the bricklayerbetter, saw.The amountof mortarrequiredis,for lowerfor masonry' The handlingof the masonryunitsthemselves example,approx.25-30o/o ' for withoutmortarto the perpendsthanfor masonis crucialto manualbricklaying. Therefore, ry with mortarto the perpends.In Germany, example, the calciumsilicateindustryhas guidancefiguresfor working grip aidswithgrip bar andthumbcomprehensive developed holeespeciallyfor theirheavyblocksfor brick- hourshavebeenpublishedby the Federal Pay.These Committeefor Performance-linked layersto be ableto handlethe blockseasily. mix-: The bricklayerno longerhasto relyon the fric- includeancillaryworksuch as instruction, ing mortar,movingscaffolds,settingout and tion betweenhisfingersand the surfaceof the etc. cleaningtheworkplace buildingopenings, masonryunitto grip it. Apartfromthat,there of the Thefiguresclearlyrevealthe influences are also blockswith grip aids at the bottomfor sizeof the masonryunit;whetherbricklayingis whenthe bricklayerhasto workon sections carriedout by handor witha handlingdevice; m o r e t h a n lm h i g h . the use of thin-bedmortarand the omissionof Above'acertainweight,handlingdevicesare mortarto the perpends(seefig.2.5.14).The usedto reducethe physicalstrainof lifting speeding-upof operationswhen usinglargesuch heavymasonryunits.At the sametime, productivityis improved(see"Large-format unitscan be formatinsteadof small-format Furtherrationalization measuresfor attributedto the sizeof the unitsbut alsothe elements"). bricklayingare the useof masonrywithoutmor- techniqueof layingrowsof unitsin thin-bed tar to the perpends(see"Layingwithoutmortar modar.The economicadvantagegrowswith accuracyof the masonry to the perpends"), the useof thin-bedmasonry the manufacturing unitsbecauseas deviationsdiminishso the and the omissionof bondedintersections junctions"). mortarbed can be reducedto a minimum:savbetweenwalls(see"Butt-jointed ings in time and materialsarethe result.At the Buildingwallswithoutmortarto the perpends sametime,the wall becomesmorehomogeinvolvesusingmasonryunitswith an integral thisimpliesin neous- withallthe advantages tongueand groovesystem,whichcan then be and buildingscience. termsof structure interlocked withoutusingmortar.Tiltedbricks areavoidedby guidingeachtongueand groovetogether, whichhelpsproducea.plane Organizing thebuitding site andbtuitding wall surface.The construction of masonrywith operations of masonryalsomeans Rationalconstruction conventional 10-12mm perpendsand bed jointsmeansthat 55% of the bricklayer's time is carefulplanningof siteand operationsin order to avoidframeworkconditionsthat makeit spentwiththe mortar.The use of the thin-bed Thisincludesthe right difficult. withtongueand unnecessarily techniquein conjunction timely groovemasonryunitscutsthe consumption of use of personnel;choiceof materials;

156

I

measures Rationalization

organization and suitablelocationof stored preparations materials; for optimumuse of (theuse of premixedmortar,pretreatmaterials mentof masonryunitsetc.);and the rightuse of resources for bricklayingoperations(e.9. handlingdevices,workingplatforms,mortar sledgeetc.).Disruptions to on-siteoperations havea greatereffecton the degreeof rationalizationwhenusinglarge-format masonryunits, whichresultin fewerworkinghoursper m2of wall,thanwhenworkingwith smail-format units. Thecorrectprovisionof masonryunitsand mortarat the righttime,in sufficientquantities andat the rightplaceis especiallyimportantif the bricklayeris to avoidunnecessary walking andmovements whenworking.Thisis alsotrue whenusinghandlingdevices.To achieveopti. mumhandling times,it mustbe ensuredthateachdeliveryof masonryunitsis stackedat theplaceof work in a rowwithoutany gaps. Thisguarantees thatthe optimumnumberof unitsis laidper handlingroutinewiththe preset handlingparameters. However,too many materials storedwithinthe buildingcan alsobe a disadvantage becausethis can hamperthe movement of scaffoldsor handlingdevices. Thedistancebetweenbricklayersshouldbe about2,5-3.0m in orderto achievea regular workingrhythm,One bricklayerper 3.0 m of walllengthbringsabouta 25/o increasein performanceoverone bricklayerper 2.0 m becausethereare lessinterruptions to the workingrhythm. Theuseof a mortarsledgemeansthatthe distancebetweenbricklayersand to the tub of mortarcan be increasedstillfurtherbecause, withonefilling,longerlengthsof wallcan be providedwitha constantbed of mortarthan is thecasewhenusinga trowel.The bricklayer hasto walkand movelessand so the working rhythmis againmademoreconsistent. Scaffolds Theheightof the work is criticalto the performance,fatigueand healthof the bricklayer,

particularly when layinglarge-format masonry units.The timeand effortrequiredto lay a unit is lowestfor workingheightsbetween600 and 800 mm.Scaffoldheightsshouldbe variable so thatthis optimumworkingheightcan be maintainedfor the entirewall.Modernsteel scaffoldsare usefulherebeeausethey permit scaffoldboardsto be placedevery500 mm in height.In addition,eltensionbracketscan be suspended500 mm beloweachworkinglevel on thewallsideto avoidunnecessary bending, Trestlesand scaffoldson screwsupportswith infiniteheightadjustmentmeanthatthe working heightcan be adjustedto suitthe bricklayer,and so improvesthe ergonomicsof the WOTK.

ln contrastto scaffoldson adjustablesupports, the bricklayer'splatformwith or withoutintegral hoistprovidesa largerworkingareaenabling the buildingof wallsup to 4.0 m long.Such olatformsalsohavetheirown wheelsand so can be readilymovedto a new location,or easilyliftedby crane- representing a major economicadvantage.Withan integralhoist, evenlargermasonryformatscan be laid quickly, accuratelyand withoutfatigue. Templates The buildingof cornersor windowand door revealsare particularly complicatedoperations becauseof the amountof plumbingand measuringworkinvolved. Reusable cornerand openingtemplates, whichindicatethe vertical and horizontalpositionsof coursesand units, can makesuchworkmucheasier.Buildingthe cornersfirstwiththe associatedrackingback is no longernecessary. Whenlayingthe base course,in whichany unevenness in thefloor hasto be comoensated for and so establishes the basisfor the accuracyof subsequent courses,a noticeablerationalization effectis achievedwhenusinga template, aboveall in the nextcourse.An increasein productivityis particularly evidentwhen doorsand windows, or at leasttheirframes,are incorporated as

prefabricated elementsand simplybuiltaround in oneooeration.

Rational working with large-format masonry units

Large-format masonryunitqand elementsare thosewith lengthsof 498-998mm and heights of 373-623mm.The lengthand heightresult fromthe useof thin-bedmortarwith bed joint of 1-3mm.To and perpendthicknesses reducecostsstillfurther,the perpendsarefrequentlytongueand grooveunitsbuttedtogetheleer withoutmortar(see"Large-format ments"). Thehighlayingrateswithhandlingdevices and two-manteams,the useof thin-bedmortar and the reductionin subsequentworkowingto the simpleand accuratelayingof the unitsare possibilities whichcan be the rationalization expectedfromthe use of large{ormatmasonry units.The rationallayingprocessmeansthat a lengthof up to 1.25m of masonryin course heightsof 375-750mm can be constructedin one operation.Thiscorrespondsto ratesof up to approx.0.94m2of finishedmasonryper for operation.Thisis especiallyworthwhile largeuninterrupted areasof wall,but in other effectcan stillbe situationsthe rationalization guaranteedby usingsupplementary formats, make-uppiecesor specials. Thetwo-manteamrationalizes bricklaying activitiesbecauseone manoperatesthe hanfor dlingdeviceand is onlyresponsible preparatorywork (supplyingmasonryunitsand them moftar,pickingup unitsand transporting to the placewherethey areto be laid),while the otherman carriesout the actualbricklaythe layerof mortarwitha ing,i,e.spreading mortarsledgeor similartool,layingand alignworkingratesof ing the units,Consequently, flatwalls approx.0.33h/m2for uninterrupted andO.42h/m2'for otherwallscan be achieved. In orderto limitthe physicalstrainon the brickmasonryunits layer,the useof large-format has led to the introduction of a maximumper-

Thebuildingof masonry

2.5.15 Installation drawingsfor modularmasonry Calciumsilicategauged eiementwall with few interruptions

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missible weight- includinglevelsof moisture commonon site- for masonryunitswhen laying by hand,Themaximum weightlimitsare mandatoryand are stipulatedin an information sheetpublishedby the Bau-Berufsgenossenschaften(Building Employers' LiabilityInsuranceAssociations) [132],and are basedon extensiveergonomicstudies.The informa,tion sheetdistinguishes betweenthe one-handand the two-handlift. The one-handliftmeansthatthe masonryunit can be pickedup withone handand laidwithphysicalstrain.Themaximum outunnecessary permissible weightof a unltis 7.5 kg for a grip widthof up to 70 mm, and 6.0 kg for a grip w i d t ho f u p t o 1 1 5m m . Thetwo-handlift meansthatthe masonryunit exceedsthe maximumvaluesfor the one-hand lift.The maximumweightof a unitis 25 kg. Suchunitsmustbe providedwithgripaidsor be designedin sucha way thattheycan be grippedin bothhandsusingsuitabletoolsand laidmanually, Heavyunitsshouldbe liftedand laidby meansof a handlingdevice.

2.5.16 Prefabricatedsyslemwalls

bricklayerdespitethe fact that improvedproductivityis expectedfroma smallernumberof Theuseof a handlingdevicein a bricklayers. to moreratronal two-manteamonly contributes masonryconstruction whenthe perpends makeuse of the tongueand groovesystem withoutmodar(becauseseveralunitsare grippedsimultaneously), whentheteamis fully familiarwiththis systemand eachother,and whena continuoustransportchainfromproTherefore, ductionto placementis guaranteed. the groupsof masonryunitsshouldbe aligned in rowswiththe tongueand grooveend faces interlocking so thatthey can be readilylifted intoplaceby the handlingdevice.Thefastest workingtimesareachievedwhenthe groupsof masonryunitsare stackedbetweenthe hanHowever, it dlingdeviceandthe bricklayer. arrangeshouldbe notedthat a concentrated mentof masonryunitsand handlingdevice placesa heavyloadon the floorwhichmay needto be carriedby temporaryadditional supportsbeneaththe floor.Adequatecirculation zonesare necessaryin orderto be ableto movethe handlingdevicefromplaceto place. wall interThis is helpedby usingbutt-jointed sections,whichavoidthe needfor projecting rackingor toothedreturns,so that crosswalls can be builtat a laterdate.

bondingbecausethe lowernumberof perpends(andfrequently the useof perpends for withoutmortar)meansfeweropporiunities alongthe lengthof the wall.This compensation capacityof the masonlimitsthe load-carrying ry. large-format unitsmustbe diConsequently, videdwith a bolsterchiselor a mason'shamfor thin-bed meror betterstill- especially masonry- by accuratesawing.Handsawswith a hardenedblade,diamondcuttingdiscs, bandsawsor chainsawsmay be used.Clean edgescan be producedwiththe aid of guides and templates.Cutiingdiscsgenerallylast longerthan bandsawsor chainsaws.

Modular masonry The ideaof modularmasonrywas developed by the calciumsilicateand autoclavedaerated The benefitthat modular concreteindustries. is thatthe masonrybringsto rationalization masonryunitsfor eachwallare large-format wall "kits", deliveredto siteas factory-made includingall make-upand complementary instalunits,togetherwith computer-produced Masonryunit handlingdevices lationdrawingsfor a fixedprice(see2.5.15). Theuseof liftingequipment or handling of the masonry ln addition,the manufacturer devicesis necessaryfor masonryunitformats unitsprovidesthethin-bedmortar,handling largerthan16 DFfor 240mm thickwallsand devicesand accessories. 10 DFfor 365 mm thickwallsor for masonry layout Thedesignof thewalls(dimensions, Thecuttingof large-formatmasonryunits unitsweighingmorethan25 kg.Travelling and sizesof openings)mustbe coordinated mini-cranes with a load-carrying capacityof up The productionof propermasonrybonds,as withthe buildingsystemor the large-format to 300 kg situatedon the respectivefloorare well as the needto constructgivenwall and the numberof precut unitsin orderto minimize to divide, increasingly beingemployedfor thiswork. columnsizes,makesit necessary unitsand hence make-upand complementary Depending units.Whilesmallon the sizeof the units,up to five cut and bevellarge-format the cost of materials.Flatpanelsof masonry large-format unitscan be grippedand laidside formatunitscan be cut with a brickor scutch are in cellularconstruction thisis nota suitablemethodfor large- withoutinterruptions by sidein one lift,i.e.approx.1 m2of wallarea hammer, advantageous. can be producedin two lifts.Handlingdevices formatunitsbecauseit wouldcreatetoo much simdrawingsand instructions wastage.Moreover,cuttingwith a The installation are normallyusedin conjunctionwiththe twounnecessary In mason- plifyand acceleratethe erectionof masonry manteamsdescribedabove.Theyconsiderhammeror similartoolis inaccurate. unitsdeliveredas kits.This leadsto a unitsthis leadsto incorrect ablyrelievethe physicalstrainon the individual ry of large-format

158

Rationalization measures

2,5,17 Gable in the form of a clav brickworkoanel

system) 2.5.18 Clayfacade elements(Schatz-Preton

detachedhouseto be completedin just3-5 arerequired days.Onlyminimalsitefacilities polluand at the sametimethe environmental tion due to noiseand dirtfromthe bllildingsite is minimized.Anothercost-savingresultsfrom meansthe the fact thatfactoryprefabrication areessentially drywhendelivcomponents ered,whichmeansthatlessenergyis required Dry walling for dryingoutthe building(seefigs.2.5.16 and 2.5.17). is builtby layingmasonryunitsin a bondbut single-leaf withoutany mortarto the perpendsor the bed Besidestheirusefor loadbearing, joints.To achievethis,the masonryunitsmust elementsare increasmasonry,prefabricated Prefabric ated constru ction exhibita veryhighstandardof qualitywith The advantagesand economiceffectiveness inglybeingusedfor curtainwallmasonry - up to 8.0m regardto deviationsfromthe intendedheight lie in the rational facades.Suchfacadeelements of orefabricated construction prefabrication dimensions and in termsof theflatnessand of wallelements underoptimum, longand 3.6m high- are producedrationally parallelism of bed faces.Layingthe unitswith- industrial conditionsin the factory,thefasterec- and unaffectedby the weatherin the factory for reinforced outmortarto perpendsor bed jointsachieves tionusingcranesandthesubsequent simple accordingto the guidelines facingor engineermasonrywithfrost-resistant furtherrationalization in the construction of structuralconnectionof elementson siteto ing bricks.Factoryproductionensuresa conmasonry wall or structure. becausethe operations for supplying thusforma homogeneous outerleafwithrespect themortar,applyingit and removingsurplus in the factory sistentand high-quality The elementsare manufactured mortarafterlayingthe unitsareall eliminated, as brickworkpanels,cast panelsor composite to jointpattern,colourof unitsand mortar,full panels(see"Prefabricated Thisimprovesthe ergonomicsof bricklaying masonryelements") jointswithoutvoids,evenjointingetc.ln addi(number tion,blinds,lintelsand archesas wellas of bendingandturningmovements) to matchthe respectivestoreyheightsand (seefig. specialtexturescan be incorporated and hencemakesthe workingrhythmof the incorporateall necessaryopeningsand ser2.5.18). bricklayermoreuniform.Thisleadsto lesstime vice ducts.Theyare reinforcedhorizontally beingrequiredto constructeachsquaremetre and verticallyfor transportand erectlon.Indusof wall.In addition, the omission of thin-bed trialprefabrication renderspossiblethe useof (e.9.masonry mortarsavesnot only labourcostsbut material computer-assisted machinery costsas well. robots)to achievea high dailyoutputwith a As so far thereis very littleexperienceof dry highstandardof qualitybut at the consistently wallingin practice,its useis currently regulsametime low labourcosts. atedby way of generalbuildingauthoritycerDelivering the elements to the buildingsite"just tificates,Theserestrictthe use of dry walling in time"andtheirrapidand economicerection to buildingswith up to threestoreysor a speedsup progresson siteand requiresonlya heightabovegroundlevelof max.10 m, to few personnel. Smootherectionon sitedemands good preparations (instrugtion clearstoreyheightsof max.2.75m, and to of personnel, floorspansof max.6.0 m, Apartfromthat, specification of erectionprocedure,preparadrywallingmay not be usedfor reinforced tion of cranehardstanding and temporarysupportsetc.)and usuallythe useof a mobile masonry, vaulting, arches,brickarchfloors or cnrmneys. crane.Abovebasementlevel,this methodof Drywallingmustbe loadedby floorsalongits construction allowsthe primarystructureof a considerable reduction in labourcosts,also helpedby the complementary unitssupplied. ln addition, cuttingthe unitson siteand the costlydisposalof wasteare avoided.The simple installation of wall kitscan also be carried out by the unskilledin a "do-it-yourself" type of construction, whichagainsaveslabourcosts.

entirelength,wherebythe depthof bearingfor wallswithfloorloadsto one side onlymustbe at leasthalfthe thicknessof the wallor 120mm, Thefloors(alsoroofs)are to be formedas rigid plates- equivalent (e.9.structurally measures designedcappingbeams)arenotpermitted. Thestability of drywallingshouldbe verified by way of variouscomponenttestsas well as specialstructuralanalyseswith regardto bucklinglengths,bondsetc.[79].

159