Bushfire Attack Levels
Bushfire attack levels (BAL) measure a building's potential exposure to a bushfire in terms of embers, radiant heat and direct flame. The BAL rating is determined by a combination of factors described in detail in the Australian Standard AS3959-2009.
BAL rating of an area
The BAL rating assigned to an area establishes the minimum requirements for construction including the species of timber that must be used, the dimensions of the timber, and specific construction methods required to achieve the BAL rating.
The Australian Standard AS3959-2009 identifies 6 BAL levels:
BAL - LOW BAL - 12.5 BAL - 19 BAL - 29 BAL - 40 BAL - FZ
The most common being BAL - 12.5, 19 and 29.
BAL 12.5 & 19
To achieve BAL 12.5 & 19
For General Timber Use - Timber must have a density of 750 kg/m3 or greater.
For Joinery Timber (Windows & Doors only) - Timber must have a density of 650 kg/m3 or greater.
Timbers classified as having a BAL 29 rating have an inherent resistance to fire. These timbers are:
Blackbutt Kwila (Merbau) Red Ironbark Spotted Gum
River Redgum Silvertop Ash Turpentine