Timber in Bushfire Prone Areas

Australia has a long history of bushfires that spreads back far into our pre-colonial history. They have become well entrenched in the Australian psyche with the ‘Bushfire Season’ becoming synonymous with the hot northerlies of late spring and summer. While global warming continues to increase the frequencey and severity of bushfires, it is important to recognise that the material choices made during design and construction in bushfire prone areas can have a significant impact on the safety of people and buildings.

Since the Black Saturday bushfires of 2009, regulations in regards to design and material choice have increased significantly. If you live in an area that has been defined to be bushfire-prone, you are now subject to a Bushfire Attack Level (BAL) score that determines the exact type of materials you are allowed to use. This ranking takes into account a large range of factors, including the rural region, surrounding vegetation type, vegetation distance and slope of site. The regulation has specific requirements for every part of a building, however a brief and non-exhaustive summary is outlined below using tables and information from AS 3959-2009 – Construction of buildings in bushfire-prone areas.

A BAL of LOW means there is insufficient risk to warrant any specific construction requirements.

A BAL of 12.5 or 19 means you have a moderate risk of fire exposure. You are allowed to use the timbers in the chart, including the highlighted bushfire resisting timbers.

A BAL of 29 means you have a high risk of fire exposure. You are allowed to use bushfire resisting timbers that are highlighted in the chart.

A BAL of 40 or FZ means you have a very high or extreme risk of fire exposure. This means timber use is heavily restricted, and non-combustible materials like masonry and steel must be used.

As you can see, Australian hardwoods have been deemed ‘bushfire-resisting’ due to the inherent properties and density of the wood. So if you’re building in a bushfire prone area, or simply want to stay as safe as possible, look no further than Blackbutt, Merbau, Red Ironbark, River Red Gum, Silvertop Ash, Spotted Gum or Turpentine.

Resources you may be interested in:

Construction of buildings in bushfire-prone areas – AS 3959-2009 // https://law.resource.org/pub/au/ibr/as.3959.2009.pdf

BAL explanation // http://www.as3959.com.au/bushfire-attack-level/

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