Bushfire-resisting timber

Bushfire-resisting timber is a short list of naturally dense, fire-resistant timber species that AS 3959 permits for certain exposed elements in bushfire-prone areas, without further protection. The species are named in Appendix F of AS 3959, and using one of them is how a timber deck, step, or similar element can be built on a higher-BAL site.

The species

AS 3959 Appendix F lists seven species (verified 2026-05-26):

Blackbutt
Kwila (merbau)
Red ironbark
River red gum
Silvertop ash
Spotted gum
Turpentine

These are dense hardwoods that resist ignition and char slowly. The most commonly specified and easiest to source are merbau, blackbutt, spotted gum, and red ironbark.

Where it can be used

Bushfire-resisting timber is permitted for exposed elements such as decking, the framing of unenclosed subfloor spaces of verandahs, decks, steps, ramps, and landings, and some external wall and decking applications. It can be used unprotected up to and including BAL-29, which is the highest level at which AS 3959 allows this timber on its own. At BAL-40 and BAL-FZ (the flame zone), timber alone is not enough, and non-combustible or otherwise protected construction is required.

So the species list is a BAL-29-and-under solution, not a flame-zone one.

For a builder

Check the BAL first. The BAL rating decides whether bushfire-resisting timber is even an option; at BAL-40 or FZ it is not.
Use the named species. Only the Appendix F species qualify; a “looks like hardwood” substitution does not meet AS 3959. Get it specified and keep the supply documentation.
It is about the element, not the whole house. The list mostly matters for decks, steps, and subfloor framing; the rest of the bushfire detailing (windows, gaps, screens) is separate.

Also known as: BRT, bushfire resistant timber.

The species

Where it can be used

For a builder

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See also

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