Choosing Bushfire Rated Building Materials

If you're building in a bushfire zone, choosing bushfire resistant building materials is of vital importance. It can be confusing, though, because to choose the right materials, you first need to assess the level of fire danger on your property.

Bushfire Attack Levels

The first thing you need to do is find out what the "bushfire attack level" (BAL) on your property is. State and local fire services can provide you with specific information for your area, but basically, a BAL score graduates from little fire danger to extreme fire danger:

• BAL Low indicates little to no fire danger
• BAL 12.5 indicates some fire danger
• BAL 19 and 29 indicate moderate to high fire danger
• BAL 40 and BAL Flame Zone indicate extreme fire danger

The building materials that you can choose will depend on the BAL. For example, some types of fire-resistant timber can be used in BAL Low to BAL 40 areas if provisions are made to minimise fire danger. In a Flame Zone, only concrete or specially designed compressed concrete panelling should be used.

Choosing Bushfire Rated Building Materials

AS 3959-2009 is the updated Australian Standards for the construction of buildings in bushfire areas. It covers every facet of construction, from design to materials. Materials are further classified according to their appropriateness for use in BAL designated areas. For example, these timbers are permitted for use in bushfire prone areas up to BAL 29:

• Blackbutt
• Merbau
• Red Ironbark
• River Red Gum
• Silvertop Ash
• Spotted Gum
• Turpentine

In BAL 40 and BAL Flame Zones, some timber can be used, but it must be in accordance with testing methods specified in AS 1530.8.1 (BAL 40) and AS 1530.8.2 (BAL Flame Zone). These Standards also apply to windows and other building materials.

It is possible for one side of your property to have a higher BAL than another. You should always build according to Standards for the highest BAL on your property. If your choice of materials is too restricted, you may be able to get a lower BAL by clearing the land.

Even if a material such as timber framing is acceptable, you may want to opt for a steel frame instead, just as an extra precaution. If fire-resistant shutters are not required, it may be a good idea to install them just in case a severe bushfire occurs.

One thing you should never do is use guesswork when choosing bushfire rated building materials. Get an architect to help you with your building design and work with your builder and architect when choosing construction materials. Make sure they are familiar with Australian Standards for building in bushfire zones and have them explain their reasons for choosing design elements and materials. You can live comfortably and safely in a bushfire zone, but only if you take every precaution first, and that requires professional expertise.