SECTION 2 SUBSTRUCTURE AND DRAINAGESection 1 of this series covered the importance of creating a solid foundation upon which to build a home. Section 2 takes this further and considers the substructure build - the part of the home that connects the structure above ground to the foundations. This includes walls, services, drains and the main ground floor - and all associated protection needed to prevent damp rising from the ground into the habitable area of the home.
2.1 WALLS&COLUMNS
2.2 WATERPROOFING&VENTILATION
2.3 SUB-FLOORSERVICES
2.4 GROUNDFLOOR
2.5 DRAINAGE
2.6 GASPRECAUTIONS
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Our series of Best Practice Guides will take you through what the Pride in the Job judges look for at each stage of construction and when considering the site manager’s overall organisation and management skills.
ThePrideintheJobmarkingsheetusedbyourjudgeshas44markinglinessplitacross9sections.Thejudgeswillgiveascoreforeachline-wherethereisnoworktomark,thatlinewillbeleftblankandnomarkgiven.Amarkof4indicatescompliancewithNHBCStandardsandwithBuildingRegulations.Amarkof5indicatesextraattentiontodetailoverandabovecompliancestandards.Amarkof6wouldindicatethatmuchofwhatthejudgeshaveseencannotbeimprovedupon.Amarklessthan4wouldindicatevaryingissuesrelatingtoworkmanshipandnon-compliancewithNHBC’sStandards-thegreatertheissueornumberofthesameissue,thelowerthemark.Thefinalscorewillbeallthemarksawardedexpressedasapercentage.
TheseGuidessetoutwhatthejudgesarelookingforwithclearhintsandtipsonthesortofpracticethatwillleadtohighermarks.
Clearlyitisimpossibleintheseshortguidestocovereverysinglepointofconstruction-wetryheretocoverthemainissuesthataretakenintoaccountwhenconsideringamarkforeachscoreline.
Whenlookingatthephotographs,considereachoninthecontextofthescorelineheading-don’tbedistractedbysomethingelsethatisn’tasgood-thatwillbemarkedaccordinglyelsewhere.
BEST PRACTICE GUIDES
2.1 WALLS & COLUMNS
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SECTION 2 - SUBSTRUCTURE AND DRAINAGE
2.1 WALLS AND COLUMNS
Images 1 and 2:Themasonryworkisexpectedtobetreatedwiththesameattentiontodetailthatitwouldbeaboveground;namelyfulljointsinblockworkandbrickwork,accuratecuttingparticularlyonsplayedbaywork,squarecorners,fullbondingwhereverpossibleandcleancavities.
InImage1,onemightquerythespacingoftheplasticvents-aretheyspacedattherightcentresforexample-andistheresufficientcrossflowofventilation.However,inthisscorelinewearejustlookingatthemasonry-issueswithventilationwouldbemarkedunderscoreline2.2.
Images 3 and 4:Continuingthethemeofsubstructurewallsandcolumns,thejudgeswilllookforconsistent,neatandaccurateserviceholesthattakeaccountofimposedloadsfromabove,whichmeansadequatebearingofanybuilt-inlintelsorcore-drilledblocks.Anyin-situreinforcedconcreteneedscaretakenwiththeplacementofsteelreinforcementwithcleanshuttering,especiallyinsituationswherethefinishedsubstructurewallswillbeunclad.Adequatevibrationpokerworkwillbeevidentonthefinishedsurfacesofthesewalls.Image3wouldbeimprovedbythebricksbeinglaidfrogupandthefrogsfilled.Considerhowneattheworkisinimage4.
Images 5, 6 and 7:Whatmarkswouldyougivetheworkinthesepictures?Althoughtheyaregenerallyasolidbuildandwouldperformforthelifeofthebuilding,theworklacksthefinesseofthepreviousfourphotographs.Image5,inouropinion,althoughcontainingneatandcleanwork,lacksthoughtinrelationtobonding,whichhasresultedintoomanystraightjointsandwouldlosemarksaccordingly.Images6and7containwhatwewouldconsidertobe‘industryaverage’workandprobablywouldonlyachieveamarkof4atbest.Theblockedairventsinimage7wouldbemarkeddowninline2.2.
ThecontrastintheworkmanshipshownintheimagesinthissectionillustratesthemeaningofPrideandthecloseattentiontodetailthatisrequiredofwinningsitemanagers.
Images 8 and 9:TheworkintheseimageswouldobviouslynotscorewellforPrideintheJobandindeedwouldwarrantamarkof3oreven2astheyarewellbelow‘industry’averagewithseriousremedialandre-buildworksrequired.Witnessingworkmanshiplikethiswouldraiseaqueryastothepresenceofaqualitycontrolsystemonsiteandthepotentialneedfortrainingortoolboxtalks.
Images 10 and 11:Splayedbaysareoneareainsubstructurewallswhereopportunitiestoscoreadditionalpointsareregularlymissed.Itisrecognisedbyourjudgesthatthisisadifficultelementtobuildinthebestwaypossible,asitrequiresanglecuttingofblockwork.Ifeffortcanbewitnessedinthisarea,thentheattentiontodetailandtheeffortwillberewarded.
Image10isanobviousdemonstrationoftheuseofpre-cutandstuckcornersonbothleavesofmasonryandthisrepresentstheideal,asidefromthisstandardofcuttingactuallybeingachievedonsite.Clearlythefrogsherehaveyettobefilled.Image11isagood,above-averageexample.
Images 12, 13 and 14:Theseshowarangeofdifferingbuildstandardswitharangeofissuesinseveraloftheexamples-suchaspoorcuts,poorjointing,missingDPMandinsufficientwallties;noneofthisworkwouldbescoredhighlybythejudges.
2.2 WATERPROOFING AND VENTILATION
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2.2 WATERPROOFING AND VENTILATION
Images 15, 16 and 17:Averyimportantpartofanybuildisthepreventionofmoistureingressintothebuildingfromtheground.Dampproofcoursesshouldbecontinuousandoverthefullwidthofthebrickorblockandmustbelocatedatthecorrectlevels.AcommonfaultistosittheDPCbackinthejoint,whichthenallowsrisingdamptobypassitandshowinthemasonryaboveDPC.Anytankingmustbeappliedandinstalledinaccordancewiththemanufacturersrecommendationswithparticularattentionpaidtolapscornersandfillets.
Judgeswilllookattheadequacyofsub-floorventilationandachievingagoodcross-flowtoensureminimalbuild-upofmoistureinthefloorvoid,inadditiontoallowingthefreeventilationofanyothergasesthatmaybuild-upbeneaththebuilding.
Telescopicventilatorsarethemostcommonformofsub-floorventilationused,andit’simportanttheyarewelljointedtoensureit’sthesub-floorthat’sventilatedandnotthebaseofthecavity.NHBCStandardsChapter5.2quotesthatventilatorsshouldbespacedatnomorethan2mcentresandwithin450mmoftheendofanywall.Inthesetwoimagesnotonlyisthetelescopicventilatorworkveryneatbutthestandardsinrelationtosubstructurebrickworkandblockwork,plusthecleanlinessofcavitiesandedgeDPMlaparealsogood.
Penetrationsthroughtankingoranyothermembraneshouldbecorrectlydesignedandformedasmoistureingressproblemscanbeveryexpensivetoremediate.DampProofMembranescanalsobeconsideredinthissection,aswellassection2.4inrelationtogroundfloors,withtheinterfacebetweenDPCsandDPMsparticularlyimportantforfirstcourseofinternalblockwork.Theattentiontodetailintheworkinimage15or16isparticularlyimpressiveandwouldprobablyscorea5or6.Image16showsagoodwayoftakinganairventthroughagasmembrane;thejudgesherewouldliketoknowthatthetapebeingusedtosealthejointsisthecorrectone,andthenprobablyawarda6.
Images 18 and 19:It’shighlyimportantthatanysleeperwallsinthesubstructureareprovidedwithvoidstoallowfullcross-flowventilation,aprovisionthatisoftenmissed.
Aminimumvoidof150mmshouldbeprovidedbelowsuspendedfloorsthoughthiswillbegreaterdependingonthevolumechangepotentialofthesoilbelow.Image19fullyillustratesthis,inadditiontogoodpositioningofDPCbeneathbeams,plusaccurateandsymmetricallayingofsubfloorservicesandearlyinsulationofwaterfeedpipes.Notealso
thelittle‘addedextra’ofdampprotectiontreatmenttotheendoftheconcretebeams.ThedemonstrationofPridewillbejudgedbyhowwellandhowneatlytheseelementsareinstalled.
Image 20:Unfortunatelythereareoccasionallyinstanceswhenevenbasicbuildingpracticesarenotachieved,thoughworkofthestandardseeninthisimageisveryrare.Thisisverypoorindeedandifconsistentlybadaroundtheplotwouldmeritascoreofjust1.
2.3 SUBFLOOR SERVICES
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2.3 SUBFLOOR SERVICES
Thejudgeswillbelookingforsubfloorservicestobecorrectlypositioned,appropriatelyinsulatedandproperlysupported,especiallywherethereislikelihoodforsettlementinthesub-soil.
Images 21 and 22:Thereisalwaysagooddebatearoundthebestwaytosupportrestbendsandwhethertheseshouldbecompletelyencapsulatedwithconcrete.Thegeneralruleofthumbistosupportfrombeneathtoensurethatanysubsequentsettlementofthegroundfrombeneaththeconcretecannotpullapartsocketedjoints,whichcouldhappenifconcreteissurroundingtherestbend.Image21lookssuperb-butcanyouspottheairventblockedbyawastepipe(righthandsideinthecornerofacrosswall).Perhapsalsothereshouldbegreaterallowanceforcrossflowventilation.Thereappearstobelittlethatcouldbeimproveduponinimage22,sothatcouldmeritascoreof6
Images 23 and 24:Thestandardsseeninimage23wouldbedifficulttobeat.Image24stillshowsgoodwork,butisitasgoodastheworkshowninimage23?Inimage24,thejudgesmightquerywhatappearstoawaterserviceconduitlocatedoutsidethefootprintoftheproperty-whichwouldnotbethecorrectplacementforit.
Images 25 and 26:ConsiderationshouldalsobegiventotherequirementsofNHBCStandardsChapter5.3.14inrelationtopipespassingthroughsubstructurewalls.Temporaryendprotectioncapsshouldbeprovidedtopreventfutureblockages.ItemswherePridecanbedemonstratedareinrelationtotheconsiderationoffinishedlevelsforcorrectdepthofservicesinstallation,suitablefallswhereappropriateandproperlong-termsupport.Thereislittlethatcouldbeimproveduponinimage25,sothejudgescouldwellawardthata6.Asmentionedabove,Inimage26thejudgesmightquerywhatappearstobeawaterserviceductoutsidethefootprintoftheproperty-andmarkitdownaccordingly.
Images 27 and 28:Acoupleofexampleswhereendprotectioncapswerenotused,despitetheverygoodworkincore-drillingblocksforthepipestopassthroughImage27showsapotentialnon-complianceonthe150mmmaximumlengthofpipetocentreoffirstsocketasperNHBCStandardsChapter5.3.14.Identifyinganon-compliancewouldbegroundstomarkabuildelementa‘3’.Thereisalsoaqueryovertheclosenessofthegasentrypipetoasubfloorvent,whichisprobablynotgoodpractice.
Image 29:Earlyinsulationofwaterfeedpipesisrecommended.Thebesttimetodothisiswhenthegroundfloorisbeinglaid,ensuringitextendsasfardownaspossibletothebend.Leavingittilllaterinthebuildrunstheriskofitbeingmissed.Thiswouldprobablyscorea3.
2.4 GROUND FLOOR
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2.4 GROUND FLOOR
Images 30, 31 and 32:Themostcommonformsofgroundfloorweseenowareconcretesuspended,in-sitususpendedandrafts.
Whereabeamandblockfloorisinstalled,anygroutingshouldbetight,fillingallvoidstopreventmovementoftheblocks.Groutingshouldbecarriedoutassoonaspracticallypossible,andcertainlybeforeanyloadingfrompalletsofbricksandblockstakesplace.Wherethesystemisoneofinsulationbetweenandsurroundingthebeams,thejudgeswilllookatthequalityandaccuracyoftheinsulation,especiallyasthiswillbeprovidingtheformworkfortheslab,plustheinsulantvalueforthefloorasawhole.
Images 33, 34, 35:Whateversuspendedsystemisused,focuswillbeonthequalityofthefittingoftheinsulation,alongwithcaretakenoncut-outsforservicepenetrations.Considerthestandardofworkseenhere,inparticularthecontrastofimage35.Inimage34,onemightquestionthelevelofthewastepipes-iftoolow,theywillbecoveredbythesubsequentscreedingwork.
Images 36, 37 and 38:OurjudgeswillalsoconsiderhowwellfloorDPMsarefinishedandprotected,andhowwellthesearedressedintocornerstopreventvoidsandthinningofslabsandscreedsattheedges.Inimages36and37lookattheattentiontodetailandhowneatthefinishedslabis.Compareandcontrastwithimage38andconsiderhowthiswouldbemarked….isthereanon-compliancehere?ThepositioningoftheDPMcertainlyappearstohavecausedthinningofthefloorslabintothecorner-verypoorpractice,whichwouldattractalowmarkfromthejudges.
Image 39:Reinforcementofslabswillbeconsidered,especiallywhereitisofthejet-floortype.ThermalbreaksatdooropeningsarealsoimportantconsiderationsasisthecontinuationofDPMsatthesepointstoensurerobustthermalanddampingressprotection.
Suspendedslabsmustbefullysupportedatthebearingsandthequalityoftheoverallfloorslabfinishwillbeconsideredatthispoint.ParticularcareshouldbetakenatfloortowallinterfacesandtheassociatedtankingandDPMdetails.
Images 40, 41 and 42:Somegoodexampleshereofwellfinishedandpresentedslabsreadyforthefollowingtrades.
2.5 DRAINAGE
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2.5 DRAINAGE
Images 43 and 44:Someverygoodexampleshereasalltheundergrounddrainage,thesupport,line,levels,terminalsandaccesschamberswillbeassessedaspartofthejudging.Thebeddingmustbeofthecorrectsizeandtypeforthepipesbeinglaid,andallaccesspointsshouldhaveopeningssealedduringtheconstructionprocesstoavoiddamageandentryofmaterials.
Noteintheseimageshowthesettingoutoftheaccesschambersisbeingcarriedoutwithfineprecision,andthepiperunsparallelandencasedinfullcorrectbeddingmaterial.Takingextracarewiththesettingoutatthisstagewillreapbenefitsatthefinalstagesoflandscapingwithmanholesbeingmoreaestheticallyplacedwithinpathsanddrives(seeSection8.2).
Images 45 and 46:Excessivelytightbendsshouldbeavoided,andalltherequirementsofNHBCStandardsChapter5.3mustbecompliedwithforrelevantsituations.
Image45showsthatadifferentsystemhasbeenusedforclosingthegapsaroundthesubstructureservicepenetrations.Considerationshouldalwaysbegiveninrelationtotherigidmaterialusedastoitsresistancetoverminentryandthisisaquestionourjudgesarelikelytoask.Image46showsveryneatset-uptotheworks.Prideisdefinitelydemonstratedinbothoftheseimages.
Images 47 and 48: Settingoutconsiderationsformanholessoasnottocreateawkwardlandscapeorfootpathdetailswillbetakenintoconsiderationformarking.Theseimagesshowgreatattentiontodetail,plusexcellentexecutionoftheworksandtheprotectiongiventothelidsofmanholeandotheraccesspoints.
Thefundamentalconsiderationwithdrainageshouldbeforlong-termperformancewithouttheneedforrepair,asfutureproblemswithdrainageelementscanbeveryexpensiveanddisruptivetofix.
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2.6 GAS PRECAUTION
Normallytheinstallationofgasmembranesiscarriedoutandsigned-offbythird-partycontractors,butthesitemanagementteammustalwaysmakethemselvesawareoftheimportantitemstoinspectforaqualityinstall.
Theusualgasestobedealtwitharemethaneandradonwhichareinvisibleandodourless,sothesealingoflapsisimperative.AtDPClevel,acavitytrayisofteninvolvedinthelaps,sothistoomustbesealedtothegasmembrane.
Serviceentrypointsthroughagasmembranearenownormallyprovidedforbyproprietarysectionsandmouldingswhichhasbeenahugestepforforwardtoaidquality.Howevertheystillneedtobeinstalledcorrectly,soadditionalfocusisrequiredhere.
Itgoeswithoutsayingthatgasmembranesareinstalledearlyoninthebuildandatapointwheredamageishighlylikelyifnotprotected.Thejudgeswillbelookingforevidenceofthiswithcreditgivenwherearobustprotectionregimeisbeingemployed.
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GOOD LUCK!
R387 12/20
Wehopeyouhavefoundthisbestpracticeguideusefulingainingabetterunderstandingofwhatthejudgesarelookingforateachstageofconstruction.
Remember,thesixcharacteristicsthejudgesarelookingforinasitemanagerare:
■ Consistency
■ Attentiontodetail
■ Technicalexpertise
■ Leadership
■ Interpretation
■ HealthandSafety
WewishyoualltheverybestinthePrideintheJobcompetitionasyoustriveeitherforyourveryfirstwinortorepeatorimproveonyourperformanceinpreviousyears.