Bushfire Attack Level (BAL) Assessment Guide

The Building Code of Australia 2016 Part 3.7.4.0 Bushfire Area outlines a requirement through AS 3959 ‘Construction of Buildings in a Bushfire-Prone Area’ that any residential development which is located in a designated bushfire prone area must meet the minimum construction standards pertaining to the applicable BAL rating.

There are 6 ratings which set out varying construction requirements, which are as follows.

BAL LOW

BAL 12.5

BAL 19

BAL 29

BAL 40

BAL Flame Zone (FZ)


Guide to assessing a property’s Bushfire Attack Level (BAL) 

These Individual Levels are based on:

  • The region where you live;
  • The vegetation type around your property;
  • The distance from your home to individual vegetation types; and
  • Slope of the property.

The aim of the residential building standard Australian Standard, AS 3959-2009, is to improve the ability of buildings to withstand attack from bushfires. This will provide greater protection for the occupants of a building while the fire front passes as well as the buildings itself.

The Standard sets out construction requirements based on Bushfire Attack Levels (BAL). The BAL takes into consideration a number of factors including the fire danger index, the slope of land, types of surrounding vegetation and its proximity to any building. 


Levels of BAL Attack

Bushfire Attack Level (BAL) 

   

Description of Predictated Bushfire Attack & Levels of Exposure 

 
     

BAL-LOW 

    There is insufficient risk to warrant specific construction requirements 
 
     

BAL- 12.5 

    Ember Attack 
 
     

BAL- 19 

    Increasing levels of ember attack and burning debris ignited by windborne embers together with increasing heat flux between 12.5 and 19 kWm2 
 
     

BAL- 29 

    Increasing levels of ember attack and burning debris ignited by windborne embers together with increasing heat flux between 19 and 29kWm2
 
     

BAL- 40 

    Increasing levels of ember attack and burning debris ignited by windborne embers together with increasing  heat flux with the increased likelihood of exposure to flames 
 
     

BAL- FZ 

    Direct exposure to flames from fire front in addition to heat flux and ember attack  

A site assessment can be made by the WA BAL team which will determine the construction methods that must be used. Once a bushfire attack level has been determined, WABAL will be able to guide you on the steps that should be taken during the construction or retrofitting of your home, which will lower the risk associated with living in a bushfire-prone area. A BAL compliance report will assertain whether the home is designed to be constructed in accordance with AS3959. This report will form part of a BA3, also known as a Certificate of Design Compliance (CDC)