Construction of buildings in bushfire-prone areas
Construction requirements at each Bushfire Attack Level (BAL).
Overview
AS 3959 first sets out how to determine the Bushfire Attack Level (BAL) for a site, then specifies the construction requirements for each level — BAL-LOW, BAL-12.5, BAL-19, BAL-29, BAL-40, and BAL-FZ (Flame Zone). Requirements escalate sharply with BAL: at BAL-29 and above, costs and constraints can be significant.
Key Requirements
- BAL determination using site assessment (vegetation type, distance, slope).
- Windows, doors, decking, subfloor and roof requirements at each BAL.
- BAL-12.5: ember protection (mesh, sealed openings).
- BAL-19/29: bushfire shutters, toughened glass, non-combustible cladding in some cases.
- BAL-40/FZ: substantial fire-resistant construction.
How it's used in the NCC
Called up by Section 9 of the Housing Provisions where the site is in a designated bushfire-prone area.
Practical Notes
- Confirm BAL before client signs off on cladding, window and decking selections — major cost driver.
- BAL assessments are time-stamped to vegetation — replanting or land changes can shift the BAL later.
- Some skylights and rooflights are not rated for higher BAL — check carefully.
Where to obtain
The full text of AS 3959 is published by Standards Australia and must be purchased — typical price A$150–400 per part. Always work from the current edition referenced in the NCC, not an older one.