What is BAL rating and does it affect my renovation?

Where land is mapped as bushfire prone, a bushfire attack level is assessed for the site and it drives construction requirements. The levels run from low through to flame zone, and each step adds requirements and cost.

What determines it

• The vegetation type and density around the site.
• The distance from that vegetation to the building.
• The slope of the land underneath the vegetation, since fire moves faster uphill.
• The fire danger index applicable to the region.

What changes as the level rises

• External wall and roof materials, and the sealing of gaps that embers could enter.
• Windows and doors, including glass thickness, screens and frame materials.
• Decking material and subfloor enclosure.
• Roof space and subfloor vents, which need ember-proof mesh.
• Water supply provisions and access requirements on some sites.

Where it catches people

The requirement applies to additions and to some replacement work, not only to new houses. Replacing windows, rebuilding a deck or adding a room on a bushfire prone site can trigger it. And the assessment depends on the vegetation at the time, so a neighbour clearing or replanting can change the rating between one project and the next.