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Timber Merchants Association

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.

Australian Standards

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.

BAL 29

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

Further Information
Australian Standard
   AS3959-2009
Building with Timber in 
  Bushfire-prone areas
 Timber Housing in
Bushfire-prone areas