best practice section 2 substructure guides and …

BEST PRACTICE GUIDES

SECTION 2 SUBSTRUCTURE AND DRAINAGE

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

BESTPRACTICEGUIDES-SECTION2

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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

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2.1 WALLS & COLUMNS

2.1 WALLS & COLUMNS

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2.1 WALLS AND COLUMNS – SPLAYED BAYS

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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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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

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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.

best practice section 2 substructure guides and …

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