Timber Solutions should give broadly similar bracing values to Australian Standard 1684. If you could send a PDF to expert@naturallybetter.com.au we will see if we can work out why you are getting different results.
Timber Solutions Question
When using the Timber Solutions software I receive different values to long hand. These differences are quite considerable. Happy to send through PDF to see and show.
Question
I am confused as to what I need my deck joists to be made from in a BAL 12.5 area. The deck is 2.7m from ground and will be decked with spotted gum or other such timber that will meet requirements. However I see some places that say any joists can be used and others that say f27 hardwood needs to be used. For cost I am hoping for h3 treated pine. My posts and bearers are made from galvanised steel.
Australian Standard 3959:2018, Construction of buildings in bushfire-prone areas, is quite clear on this point. In BAL-12.5 areas the Standard "does not provide construction requirements for the framing of verandahs, decks, ramps or landings (ie. bearers and joists)" - clause 5.7.3.2. In other words you can use any timber, including H3 treated pine. If the space under the deck is enclosed with timber cladding, then any part of the enclosure that is less than 400mm from the ground must be one of the seven bushfire-resisting timbers, or a timber with a density of 750kg/m3 or greater - not necessarily F27 hardwood, although most F27 hardwoods would meet the density requirement.
BAL 12.5 deck Question
On a residential home when talking about the roof batten is it classed as part of the roof frame/structure?
I have spoken to the Australian building codes board who sent me this response:
On 27 Apr 2020, at 1:24 pm, NCC
Further to your question about roof battens, please refer to Clause 7.3.15 of AS 1684.2:2010 Residential timber-framed construction – Non-cyclonic areas. This clause provides the method of determining the size of timber roof battens, by reference to Span Table 32 for battens supporting roofing loads only for spans up to 1200 mm.
Regards
Australian Building Codes Board
He stated on the phone that the battens are 100% a part of the roof frame and structure but they are unable to put it in to writing, but obviously nice enough to email this to show his view.
There is several sections in the Australian standards that provide evidence of the battens being a part of the roof structure, however there is a certain group of building inspectors attempting to manipulate the wording and have it believed they are part of the roof cover rather than the roof framing/structure. Is this something you could confirm officially in writing to me via email dean@powerdriveroofing.com.au it would be much appreciated.
In our opinion tile battens and/or roof battens are definitely part of the roof structure. That is why timber roof battens are included in the span tables in Australian Standard 1684, along with rafters, ceiling joists and other roofing members. Your building inspector may consider roof battens are not part of the roof structure because they are often supplied by the roofing company, rather than the timber supplier. And, of course, if the battens are steel rather than timber they may come as a package with the roofing material. However, whether they are part of the roof structure or part of the roof cover seems to be splitting hairs. They have a structural function no matter who supplies them, or what material they are made of.
Roof battens
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