What is the Bushfire Attack Level (BAL)

bushfire 1

The BAL is a number that indicates how severely a bush fire is likely to affect your new house. It comes from the Australian Standard AS3959 – 2009.

The number is calculated by considering the following  factors:

  1. The Fire Danger Index (FDI)   The probability of a bushfire starting, speed of spread, intensity and difficulty of fighting the fire.For Victoria the FDI is 50 for an alpine area or 100 elsewhere. For other states you will need to check with your state regulations.
  2. Classification of Nearest Vegetation   In all directions. 
    • A – Forest
    • B – Woodland
    • C – Shrubland
    • D – Scrub
    • E – Mallee / Mulga
    • F – Rain Forest
    • G – Grassland
  3. Distance to Vegetation   Horizontal distance to the main part of the house.
  4. Slope   This is the slope of the vegetation, not the slope of the area between the vegetation and the house.

Downslope example

In the above example this is a ‘Down Slope’ as the slope of the vegetated area is Down as it goes away from the house ((Even though the intervening space slopes up). ‘Down Slopes’ are higher risk than ‘Up Slopes’ because fire moves quicker going up hill.

By the use of tables the FDI can be calculated for each direction with the highest value being the overall FDI.

Although it is possible to get guides and do it yourself (For example: Victorian Building Authority) I think where safety is involved it’s worth getting an expert in. They will be able to do the assessment and give you advice on requirements and improvements.


This link explains the various BAL ‘Scores’