Bushfires are a natural occurance that is a vital process in the replenishment of soil with nutrients and ridding the land of waste. However, with changing landscapes and changing climates, Bushfires have become more unpredictable and ferocious. Due to this change, Standards have been developed to help ensure safety for people and structures in the event of a bushfire. These standards are known as Bushfire Attack Levels (BAL). BAL is used to determine the appropriate level of fire safe construction required relative to the potential bushfire attack.
How are bushfire attack levels determined?
BAL differentiates between buildings and can be allocated into 1 of 6 danger levels. From lowest to highest, the danger levels are:
- BAL – Low
- BAL – 12.5
- BAL – 19
- BAL – 29
- BAL – 40
- BAL – FZ
These levels are allocated based on 4 key points:
- Type of vegetation surrounding the building.
- The slope of the vegetation surrounding the building.
- The distance of the vegetation from the building.
- Fire Danger Index (FDI) for your local council area.
For a basic estimate of your BAL visit the NSW Rural Bushfire Service ‘bushfire prone land tool’. For a more detailed analysis we would suggest contacting a bushfire consultant. It is important to note that BAL needs to be calculated based on individual site circumstances at the time of the application.
What are the BAL Levels?
BAL – Low
Minimal attack from radiant heat and flame due to the distance of the site from vegetation, although some attack from debris is possible. There is insufficient threat to warrant specific construction requirements, but residents should still do basic property protection.
BAL – 12.5
Attack by burning debris is significant with low levels of radiant heat (not greater than 12.5kW/ m2). Radiant heat is unlikely to threaten building elements (i.e. unscreened glass). Specific construction requirements for ember protection and accumulation of debris are warranted (level 2 construction standards)
BAL – 19
Attack from burning debris is significant with an increased radiant heat levels (not greater than 19kW/m2) threatening some building elements. Specific construction requirements for protection against ember and radiant heat are warranted (level 2 construction standards).
BAL – 29
Attack by burning debris is significant and radiant heat levels (not greater than 29kW/m2) can threaten building integrity. Specific construction requirement for protection against embers and higher radiant heat are warranted. Some flame contact is possible.
BAL – 40
Increase attack from burning debris with significant radiant heat and the potential for flame contact. The extreme radiant heat and potential flame contact could threaten building integrity. Buildings must be designed and constructed in a manner that can withstand the extreme heat and potential flame contact.
BAL – FZ
Radiant heat levels will exceed 40kW/m2. Radiant heat levels and flame contact are likely to significantly threaten building integrity and result in significant risk to residents who are unlikely to be adequately protected. The flamezone is outside the scope of the BCA and the NSW Rural Bushfire Service may recommend protection measures where the applicant does not provide an adequate solution.