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We have been engaged to design an owner-occupied residence at the above-mentioned address. We have determined that the property is a BAL-40 site and will require particular attention to the materials used. Our client is the owner of Barwon Timber in Geelong. Hence, there is an even greater impetus to incorporate timber wherever possible.

Currently, we are considering a non-combustible articulated panelised cladding system. However, we would like to feature north- and south-facing timber decking, as well as timber baluster posts, window frames and garage doors. We have tried to discuss this with our fire consultant but they have not been particularly helpful. We contacted the Australian Forest Products Association regarding this request and referred to WoodSolutions instead.

We would greatly appreciate your assistance with this project.
 

Woodsolutions Answer +

BAL-40 is difficult for wood products. Timber window frames are allowed if they are protected by bushfire shutters, which themselves have to be non-combustible. Garage doors also have to be non-combustible. There are no requirements for balustrades and handrails if they are 125mm or more away from the building but if closer than that, they have to be non-combustible. Decking must either be non-combustible or part of a system shown by testing to AS 1530.8.1 to achieve BAL-40. We are not aware of any timber decking that has achieved BAL-40 in accordance with AS 1530.8.1, although jarrah decking has achieved BAL-29. Unfortunately applying a fire retardant coating doesn't make timber non-combustible, it just delays ignition. 

Bushfire BAL-40
Question

I am planning on building a fence along a boundary with a school which is classed as a Code Red School, are there any requirements for what timber I can use?
I am planning on using Cypress macrocarpa.
 

Woodsolutions Answer +

We understand the Code Red classification applies to schools that close on "Code Red Days", ie. days when weather conditions suggest there could be a risk of bushfire. The Australian Standard which bushfire regulations are based upon does not address fences, but is focussed on buildings. However the NSW Rural Fire Service has a fact sheet on fences in bushfire areas, and you might inquire whether the fire service or local Council in your area has anything similar. The NSW fact sheet can be downloaded here: https://www.rfs.nsw.gov.au/__data/assets/pdf_file/0014/4532/Fast-Fact-Fences-or-Gates-in-Bush-Fire-Prone-Areas.pdf. We are not aware of any regulatory restrictions on Cupressus macrocarpa for use in school fences but it is not considered durable enough for posts in the ground. In New Zealand macrocarpa is commonly used for above-ground purposes such as weatherboards, but it is not recommended for use in the ground. More info can be found here -  http://www.nzwood.co.nz/forestry-2/macrocarpa/

Macrocarpa
Question

We are designing an external covered area for a market food court. We have been told by the Building Surveyor that the external columns (and presumably any trusses / portal frames) need to have a fire rating of 180 min. Can this be achieved with timber columns? or do we need to move to steel or concrete columns. The area will also be fitted with fire sprinklers throughout. Any advice would be greatly appreciated.

Woodsolutions Answer +

It is possible to design timber members to have a specific fire rating. The procedure is outlined in Australian Standard 1720, Part 4: Fire resistance for structural adequacy of timber members. The Standard is based on oversizing members to provide a sacrificial layer of timber. The design procedure ensures that after burning for a specified time there is sufficient sound timber remaining to support the load. We assume your Building Surveyor is correct in advising that a 3-hour fire rating is needed, given that sprinklers will be in place. No doubt that depends on the Class of building and other factors. Since the timber structure will be protected from the weather you could look into the use of fire retardant coatings, as an alternative to using AS 1720.4. A registered fire engineer could advise whether an Alternative Solution can be developed to satisfy the NCC's Performance Requirements. The procedure is described on our website here: https://www.woodsolutions.com.au/articles/fire-regulation-compliance-through-alternative-solutions

NCC Alternative Solution, AS 1720.4
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