Australia has a number of high density timbers that provide an inherent natural bushfire resistance Seven of these are defined by AS 3959–2009 as bushfire-resisting timbers (BRTs).
They are solid, dense hardwoods that performed well in extensive fire testing Both fire-retardant (FR) treated timbers and specific species can be used in many external applications. These are specified in AS 3959–2009 and summarised in this publication Lists of timber species with specified densities are given in Appendix E of AS 3959–2009 Construction of buildings in bushfire-prone areas.
The most common construction timbers are:
- Bushfire – resisting timbers* (BRTs)
Blackbutt, Kwila (Merbau), Red Ironbark, River Red Gum, Silvertop Ash, Spotted Gum, Turpentine
- Timber* species from E1: density 750 kg/m3 or greater include:
All BRTs (above) plus Brownbarrel, Grey Box, Grey Gum, Grey Ironbark, Jarrah, Manna Gum, Messmate, Mountain Grey Gum, Stringybark/s, Sugar Gum, Sydney Blue Gum
- Timber* species from E2: density 650 kg/m3 or greater include:
All species from E1 (above, including BRTs), also Alpine Ash, Slash Pine, Mountain Ash (Victorian Ash), Shining Gum, Cypress
*in solid, laminated or reconstituted form
Timber log walls (guage planed, species density of 680kg/m3 or greater at 12% moisture content) can also be used with a minimum nominal overall thickness of 70mm (at the interface of two logs) and comply up to BAL–19.
Stocked at NHS:
- Merbau 90 x 19, 140 x 25
- Blackbutt 86 x 19, 140 x 22
- Spotted Gum 86 x 19
More timbers can be obtained by special order