Book - School of Science and Technology

38 The building in winterInsulationSlab(Warm roof)VoidAsphaltVapour barrier (if required)False ceiling (optional)InsulationSlab(Inverted roof)VoidHeavy surfacingRoofing feltFalse ceiling (optional)ScreedSlabPlasterScreedGlass fibre insulationInsulation boardRoofing feltWood wool slabAsphaltWood wool slabPlaster boardAsphaltSteel deckingTiles on battens on feltRaftersJoistsGlass fibre or loosefillCorrugated sheetingAir gapPlaster boardInsulating boardFigure 2.7 Methods of applying insulation to rootsSafeguards are necessary in adopting this method of treatment, owing to the fact that rainpenetration through the outer skin will seek out any discontinuities in the injected or inbuiltmaterial and will thus allow moisture penetration to the inner skin and plaster. It has alwaysbeen a cardinal rule that mortar dropping onto wall ties and the like must be avoided in thebuilding of cavity walls. It is, in consequence, recommended that application of this form ofinsulation be entrusted only to firms approved by the British Board of Agre ment.It is, furthermore, essential that the material used be water resistant and resistant torotting, mould growth and attack by vermin. The principal danger is that of penetration,