b'BUILDING CODEitalicized(DivisionA,Section1.4.Termsregulated in these regulations) 7 . On thefunctional categories established by the and Abbreviations (Rev 2)). For example,otherhand,removingandreplacingaRCABC Roofing Practices Manual (RPM). buildingmeansanystructureusedorstructural element of a building certainlyThe RPM classifies roof systems as intendedforsupportingorshelteringqualifiesasachangethatconcernseither waterproofing or water-shedding. anyuseoroccupancy.NotethatintheCode,foreverytypeofbuildingThe latter uses gravity to shed water away thedefinitionforbuilding,thetenseis(see Objective OS2 Structural Safety8 ).fromthestructure.Water-shedding specific (present tense) and pertains toCodeobjectivesarethekeytounder- roofs are not designed to work under buildings that are already in use (usedstanding what change means 9 . anykindofhydrostaticpressureand means already constructed because itSo much for the scope of the Code.arecommonlyusedonPart9struc-is contrasted with the word intendedWhat does the Code have to say abouttures.Asphaltshingles,cedarshakes which carries a future or pre-construc- membrane roofs? and shingles and metal panel roofs are tion sense). all water-shedding materials.Alteration means a change or exten- Begin with the End Waterproofingroofsystems,on sion to any matter or thing or to anyA roof keeps the weather outside, whichthe other hand, resist hydrostatic pres-occupancy regulated by this Code. Noneis a plain way of saying that it separatessure. These roofs are usually (but not of the key words in the definition forenvironments(insidefromoutside).exclusively) flat (sloped toward drains alteration(exceptthewordbuilding)areThe Code has various things to say aboutless than 1:6), and most are insulated further defined, but notice the use ofdifferent types of roofs, but our focusbeneath the weathering surface. Some or, which means that an alteration canisonmembranesystems.Youwontareinsulatedaboveit 10 .Theweath-mean a material change in the buildingfind clear articulation in the Code aboutering surface is commonly referred to or a change in its occupancy (which meansroof types or even roof function, andas a membrane, but not all membranes the way in which the building is or willthere is an assumption that the readerarethesame;someareliquid-ap-be used). Therefore, we must take thealready has a working understanding ofplied,otherscomprisedofsheetsof commonsenseoftherequirement,membrane roof systems. Nevertheless,materialweldedtogethertoforma namely that when a thing on a buildingsincerooffunctionisausefulwaymonolithic covering (singular in form ischanged(aroof,forexample),theofunderstandingCoderequirementsand function).Code applies to the change. for membrane roofs, well rely on theMembrane-typeassembliesare As stated earlier, there are limits tousedonmostPart3buildings, theapplicationoftheCode.Changing7 Ibid andonsomePart9structures. the exterior paint colour on a building8 British Columbia Building Code, Division A, Part 1WhileDivisionB,Part9doesnotCompliance, Objectives and Functional Statements:provideexpressedorevencomplete wouldnotbeconsideredanalteration.Section 2.2. Objectives (https://free.bcpubli-For that matter, buying a new kitchencations.ca/civix/document/id/public/bcbc2018/ acceptablesolutionsformembrane rangeanddiscardingtheoldonealsobcbc_2018dap2s22). does not concern the Code (This Code9 For Code-compliant replacement roofing, see Part 3 in any of the waterproofing roof system Standards10 These are popularly referred to as Inverted Roof does not apply tomechanical or other published by the RCABC Guarantee Corp. in the RoofingMembrane Assemblies (IRMA), or alternatively as equipment and appliances not specificallyPractices Manual. Protected Membrane Roof Assemblies (PMRA).Suction PressureInternal PositivePressureWindwardLeewardWall WallImage: National Research Council (Canada).16lROOFINGBC l SUMMER 2021'