Australia has faced its fair share of bushfires over the years, impacting communities across various states and territories. These fires have led to significant human, environmental, and property losses. To mitigate risks associated with bushfires, Australian Standard 3959 (AS 3959-2009) was introduced, focusing on the construction of buildings in bushfire-prone areas. One key component of this standard is the Bushfire Attack Level (BAL) rating system.
The BAL rating is designed to assess the potential risk a home faces in the event of a bushfire. It considers factors such as ember attack, radiant heat, and direct flame contact. Essentially, it measures the level of heat flux, which is the rate of energy passing through a surface. This measurement is crucial for determining the construction requirements and building materials needed for homes in bushfire-prone areas.
There are six BAL ratings defined by the Australian Standard:
- BAL-Low: This is the lowest risk rating, where no special construction requirements are mandated, although some jurisdictions may have minimum standards.
- BAL-12.5: A low-risk rating acknowledging the potential for wind-ignited embers and burning debris. Specific construction requirements apply.
- BAL-19: Moderate risk rating with increased levels of ember attack and heat flux up to 19 kW/m². Additional construction requirements are necessary.
- BAL-29: High risk rating indicating a significant risk of property damage from bushfires, including higher levels of ember attacks and heat flux up to 29 kW/m². Extensive building requirements come into play.
- BAL-40: Very high risk rating with a strong possibility of ember attacks and direct exposure to flames, featuring a heat flux of up to 40 kW/m². Construction precautions are essential.
- BAL-FZ: Reserved for extreme locations with a high risk of ember attack and exposure to radiant heat and direct flames. Specialised construction is imperative.
Construction considerations for BAL-affected areas include the use of appropriate materials and building designs. For instance:
- Opt for non-combustible materials for external walls, roofs, gutters, and downpipes.
- Keep roof designs simple to minimize debris accumulation.
- Minimise open spaces under floors and decks.
- Eliminate gaps between walls and roofs.
- Avoid re-entrant corners to reduce fire risk.
LYSAGHT® roofing and cladding products made from COLORBOND® steel or ZINCALUME® steel are excellent choices for BAL-rated areas, as they do not ignite or contribute to the spread of fire. These products offer both safety and aesthetics, ensuring homes meet BAL requirements without compromising on design.
