A Bushfire Attack Level (BAL) Assessment consists of a certificate which is a declaration of your Bushfire Attack Level (BAL) rating and a report which demonstrates why you have been given that rating based on the classification of vegetation in your vicinity as well as the separation distance from that vegetation.
A Bushfire Attack Level (BAL) rating expresses the heat flux that a structure would be exposed to in case of a bushfire and is measured in kW/m2. The lowest rating is Bushfire Attack Level (BAL) rating of LOW which means the development is not subject to any additional construction requirements. This means it is either greater than 100 m away from any classified vegetation (50m for grassland) or a part of any of the other five exclusions stated in the AS 3959 for low threat vegetation. The next level in the Bushfire Attack Level (BAL) rating is BAL-12.5. This level is a relatively low bushfire threat rating but there is a risk of an ember attack. This means the ignition of fire from a stray ember that can float onto combustible material or into vents/weep holes, therefore, igniting building material and causing a fire which can spread rapidly.
For Bushfire Attack Level (BAL) rating of BAL 12.5, there are set construction requirements listed within the AS3959 which prevent an amber attack. These construction requirements ensure that an ember attack is averted and the building is able to withstand a heat flux of about 12.5 kW/m2 in the case of a bushfire. These requirements are listed in the AS3959 under Bushfire Attack Level (BAL) BAL-12.5 construction requirements:
- All walls exposed to a probable bushfire threat shall all be made of non-combustible material or materials specified by the AS3959
- All roof covering to be non-combustible or materials specified by the AS3959
- The correct use of bushfire shutters and screens for doors and windows
- All framing and assembly for doors and windows to be non-combustible
- All glazing used to be safety glass.
- The use of ember guards and mesh screens on all openings vents, weep holes etc.
- Joints in all joinery to be kept at a minimum size as specified by the AS3959
A Bushfire Attack Level of BAL-12.5 does not warrant very comprehensive requirements for bushfire construction. Most of the requirements are something a solid construction will already follow. The key element for Bushfire Attack Level of BAL-12.5 bushfire construction is avoiding an ember attack hence the requirement of ember guards/mesh and bushfire shutters on all openings.
If you have had a Bushfire Attack Level (BAL) Assessment completed for your development and need advice on bushfire construction requirements for your Bushfire Attack Level (BAL) rating, then contact your us your BPAD accredited Bushfire Attack Level (BAL) Assessor today for a compliance report.