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Rate and build for wildfire

Wildfire attacks a house with burning embers, radiant heat and flame contact. A rating system tells you how much protection each part of the house needs.

How

1. Australia: AS 3959 sets six Bushfire Attack Levels: BAL-LOW, BAL-12.5, BAL-19, BAL-29, BAL-40 and BAL-FZ (flame zone). The standard gives a method to find a site's BAL.
2. Each BAL sets construction rules from the sub-floor to the roof, including windows and external doors.
3. US guidance (BASC): use Class A roofing such as tile, metal or fibreglass asphalt shingles. Screen vents with mesh no larger than 1/8 inch, or use ember and flame-resistant vents.
4. Use ignition-resistant siding such as fibre cement, stucco, masonry or brick veneer. Use dual-pane windows with one tempered pane.
5. Build decks from heavy timber or noncombustible materials, and fit gutter screens.
6. Keep a noncombustible zone of 0 to 5 ft (about 1.5 m) around the house, and lay out defensible space (site-12).
7. Set the construction rating and the defensible space together, before the design is final. See also safety-5.

Do these first

• design-24
• site-12

Sources

1. Construction of buildings in bushfire-prone areas (AS 3959). Housing Industry Association, Australia, accessed 2026-11
2. Design for Wildfire Resistance (Building America Solution Center). Pacific Northwest National Laboratory for US DOE, accessed 2026-11

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