A Guide To Internal Lime Plastering - Roundtower Lime

1. G U I D E T OI N T E R N A LL I M EP L A S T E R I N G P R E P A R A T I O NO FT H EW A L LS U R F A C E S U C T I O NC O N T R O LA N DB O N D I N G S A L TC O N T A M I N A T I O N T E C H N I Q U E S O F H Y D R A U L I C L I M E P L A S T E R I N G T H O RH E L I C A LA U S T R A L I A

2. A G U I D E T O I N T E R N A L L I M E P L A S T E R I N G PREPARATIONOF THEWALLSURFACE Whereexcessiveholloworunevennessis hesuccessfulapplication, bondingand presenttheareasshouldbecorrectedby correcthardeningofhydrauliclime useofmortarandstoneorbrickslips mortars, requiresthatthebackground beddedintothemortar, withtheaimof shouldbeclean, freefromvegetation, free presentingareasonableflatbackground ofcontaminantsandreasonablydry beforeplasteringcommences throughoutthewallmass. Thewallshould bestructurallysoundandthemasonryand SuctionControlandBonding beddingmortarsingoodcondition. Beforetheapplicationofanynewlime Theapplicationofvariousdubbingout coatings, hydraulicornon-hydraulic, itis coatsshouldnotbeseenasremedialrepair vitallyimportanttochecktothedegreeof worktothemasonryorbrickwork suctionwithinthebackground, pooror background, thereplacementofmissingor excessivesuctioncanresultinaweak damagedmasonryoropenjointsshouldbe bondingwiththesubstratecausedby repairedbeforeanyplasteringofdubbing rapidde-maturingofthenewlyapplied outcoatsareapplied. render,

3. whichwillresultandaweakandpowdery mayneedtobecarriedouttheprevious interfacewhichwillleadtolaterfailureand dayorseveraltimesthroughouttheday separation. Wherethereislittleorno beforerenderingcommences. suctionfurtheractionwillberequiredto Theobjectiveofthesuctioncontrolisto helpbondthecoatingtothesubstrate. In achieveathoroughlydampsurface, but situationswheresuctionneedstobe notwet, i.e., thesurfacemustnothave controlled, wettingdownwillberequired, runningorstandingwaterremainingon ondenseblocksornearimpervious themasonryorbrick, thiswillforma masonry, simplydampeningthesurface barrierbetweenthecoatingandsubstrate, withamistspraymaybeallthatis alsolimemortarsadhereandstiffen required, butonveryporoussurfacessuch throughacertainamountofsuction.On asoldbrickworkconsiderablewettingwill denseornearimperviousbackground, it berequired. Wettingthewallbyuseofa maybenecessarytoapplya hose, workingfromthetopofthestructure, sand/splatterdashcoattothebackground downwards, toactasamechanicalkey. SALTCONTAMINATION Saltcontaminatesshouldneverbewashed Wherenewlimecoatingsaretobeapplied fromthesurface, asthiswillresultinthe tomasonrywhichissaltcontaminated, the crystallizedsaltreturningtoasolublestate masonryshouldbeallowedtodryfully andretreatingbackintotheporesofthe beforeapplyingnewrenders. Thiswill masonryorbrick. Wheredetectedonthe allowsalttobedetectedonthemasonry masonrysurface, thesaltsshouldbe andmortarjointsurfaces, ifexcessivesaltis brushedfromthesurfaceandcleaned identifiedclayorlimemortarpoulticing awayfromthestructure. mayberequired. Specialistadviceshould besought, ifthetechniqueisconsidered wheresaltisdetectedonthemortarjoints, rakeoutthejointstoadepthof50mm, as thisislikelytobeheavilycontaminated andinaweakenedconditionandrepoint.

4. TECHNIQUESOFHYDRAULICLIME PLASTERING thiscoatisappliedinacoatof Thetechniquesemployedinthe approximately10mmthickness, thiscoat applicationofhydrauliclimeplasters canbeappliedbyuseofasteeltrowelor shouldbetoensureacorrectbondingwith thrownontothewallbyuseofaharling thebackgroundwhilestrivingtominimise trowelandthenflattenedinbythesteel shrinkageandrapiddrying, these trowel. Whenthiscoathasfirmedupbut techniquesshouldbefollowedthroughout hasnotgonehard, theplasteriskeyedor theplasteringprocess. Limeplasteringis scratcheduptoproduceakeyforthe generallyappliedin3coats, butitis followingcoats. Thekeyingupiscarried commontofind2coatsorevensinglecoat outbyuseofalathscratcherorsimilar workinvernacularorearlystructures. In3 toothedinstrumentandcareshouldbe coatworkthefirstcoatonmasonryor takennottocutthroughtheplastercoat brickworkisgenerallyknownasthescratch backtothebackground. coatorrendercoat, Thekeyingupisgenerallyintheshapeofdiamondsofapproximately30mmspacing. This coatshouldbeallowedtohardenfor72hoursminimumbeforefurthercoatofplasterare applied, beforeapplyingthesecondcoatthefirstcoatshouldbecheckedforshrinkage cracks, andtheseshouldbefilledwithplasterbeforeproceedingwithfurthercoats, before thesecondcoatisappliedthefirstcoatshouldbebrusheddowntoremoveanydustwhich mayhaveblownontothesurface. Thefirstcoatshouldthenbedampeddowntoensurethat thesecondcoatisappliedtoadampbutnotwetsurface. Thissecondcoatiscalledthe floatingcoatandisthecoatwhichisstraightenedtoensureaflatandevensurface, afterthis coathasbeenstraightened, thesurfaceofthiscoatisscouredupwithatimberor polyurethanefloat (rubbingupwithafloatsimilartofinninguprender). Thepurposeofthescouringistocompacttheplasterandcounteractshrinkage. Thisprocess isgenerallyrequiredtobecarriedoutatleasttwice, duringthescouringup, anysmallholes shouldbefilledbeforethefinishingcoatisapplied. Thiscoatshouldalsobeallowedtodry andhardenfor72hoursbeforeapplyingthefinalcoat.Afteronceagaindampingdownthe floatingcoat, thefinalcoatisapplied. Thiscoatknownasthesettingcoat, isappliedintwo layers, coatoncoat, withthetrowel. Thiscoatisappliedinawaysimilartoskimming. This materialshouldbeofawetenoughconsistencytoallowalongandevenspread. Oncethe settinghasbeenapplied, itisscouredinasimilarmannerasthefloating, tocounter-act shrinkageandthenthesurfacecanbeleftwitharubbeduprenderedtypefinishorpolished smoothwithasteeltrowel.

5. GENERAL MIX GUIDE: BACKINGCOATS1ST AND2ND: 1Part RoundtowerNHL 2 or RoundtowerNHL3.5 to2Partsor 2.5PartsWashedSharpSand. Useof fibreorhairinthesecoatsis recommended. 01 FINISHCOAT 1Part RoundtowerNHL21PartFine SilicaSand OR 02 1Part LimePutty1PartFineSilica Sand OR Monolys (Roundtower'spre-mixed internalfinefinishcoat) 03

6. ROUNDTOWER NATURAL HYDRAULIC LIME IS AVAILABLE THROUGH THOR HELICACL AUSTRALIA EXCLUSIVELY. W W W . T H O R H E L I C A L . C O M . A U 1 3 0 0 9 3 7 3 4 9