b'Timber: A Natural and Safe AlternativeTimber cladding is an increasingly popular choice for Australianperformance requirements of the National Construction commercialanddomesticbuildingsduetoitsstrikingnaturalCode (NCC) for use as internal and external wall cladding.aesthetic, durability and low environmental impact. Perhaps less widely known are the strong fire-resistant qualities of timber thatThis whitepaper will outline in detail the deemed to satisfy (DtS) make it a perfect fit for fire safety in the Australian constructionsolutions for timber cladding for Class 29 constructions, as industry.Timber is an age old material and its physical propertiesoutlined in NCC Volume 1 - Section C: Fire Resistance, as well as andfireperformancequalitiesarewellunderstoodandopportunities for use outside the DtS with the development of a documented.performance solution.TheAustralianBuildingCodeBoard(ABCB)recognisesthe many applications where timber exceeds the rigorous fire safety How Does Timber Burn?productscanvapourisecausingcrackinganddangerous Tounderstandwhytimbercladdingisrecognisedforitsfireexplosions with the potential for throwing shrapnel.resistant qualities, it is important to first understand how timber burns. Timber, on the other hand, shows a controlled and slow decline instrengthproportionaltothecharlayeroftenmakingita When timber is first exposed to temperatures of above 280C,saferalternativetosomenon-combustiblematerials.Timbers the surface layer of the wood ignites and burns. This layer rapidlypredictablenatureinthecaseoffireprovidessimplicityand turns into char becoming a thermal insulator for the solid woodconfidence in the design of fire safety systems in any construction that lies beneath it. The initial charring rate quickly decreases asscenario.the charcoal layer struggles for oxygen and heat energy required to continue combustion.The natural insulating qualities of timberRedefining our Understanding of mean that whilst temperatures at the char layer may be upwardsCombustibleof 280C, there is a steep temperature gradient across the char resultinginmuchlowertemperaturesattheinnerwood.ThisIn the wake of incidents such as the 2017 Grenfell Tower fire allows the inner layer of timber to retain its structural adequacyinLondonandthepublicdebatethathasfollowed;thelabel and integrity whilst also assisting with compartmentation of heatcombustibleinrelationtoexternalcladdinghasbeenused from the fire source.synonymously with dangerous and non-compliant materials. It istherefore imperative to clarify the difference between dangerous Under the char layer, there is a layer of heated wood above 200Cmaterials used in non-compliant applications (in Grenfells case, known as the pyrolysis zone. The charring rate at the pyrolysishighly ignitable aluminum composite panels used in a high rise zone is fairly constant and is a function of density and moisturecontext) and combustible cladding materials used in compliant content of the timber. High density timbers have a much greaterapplications (such as timber cladding in a low rise context). resistance to ignition and tend to have a slower charring rate. Many non-combustible materials do not retain structural strengthTheAustralianBuildingCodesBoard(ABCB)hasproposed under high heat load which results in deformation (or meltingchangestoitsNationalConstructionCode(NCC)whichis which can cause spread of flame) and eventually collapse. Steelscheduled to come into effect in 2020. These changes will only productscandrasticallydeclineinstrengthunderheatloadsaffect buildings within Class 2 and Class 3 which are more than causing unpredictable and sudden failure. Moisture in masonry2 storeys and of Type A or Type B Construction. As at August 2019, the NCC has not changed. Standing concessions still apply Char Layer 290 Pyrolysis Zone to current builds that have been approved. No retrospective issues will arise with buildings already approved and no product will need Normal Wood to be removed/replaced after these changes come into effect.Althoughcombustible,thepredictablecharacteristicsoftimber makeiteasytomodelanddesignappropriatefireprotection systems that underpin the application limitations of the deemed to satisfy solutions for timber cladding in the NCC.The DtS solutions and verification methods defined in the NCC allow for timber cladding, such as Weathertex hardboard cladding products, to be used as part of an internal or external wall or ceiling across all construction classes. The following sections will Figure 1: Shows Zones of Burning wood step through the NCC requirements for wall cladding and present Figure from Engineered Wood Panel Association of Australia compliant applications for timber cladding in closer detail.Weathertex3|'