There is almost no greater threat to Australian homes than that of bushfires. The devastation caused by the bushfire in Victoria in 2009 was unprecedented in its intensity and the Building Code of Australia (BCA) had to be revised as a result. The new regulations include an increase in the gradation of Bushfire Attack Level (BAL) categories, so that there are now six of them. These range from low (BAL LOW) to extreme (BAL FZ or 'Fire Zone') which more accurately represents the range of threat levels a home might be under when a bushfire occurs.
How BAL ratings affect decking
The main problem faced by decks in high BAL risk areas is enclosing the sub floor space – this is a requirement for any property rated at BAL 12.5 or above. On higher rated properties, additional requirements such as non-combustible materials used in the supports and a clearance area of non-combustible material around any large glazed area such as a glass sliding door help to reduce the risk of a bushfire destroying your home.
Below is a list of the requirements that apply to decks for buildings with different BAL ratings:
| BAL ratings | Construction requirements |
|---|---|
| BAL-LOW | No special requirements |
| BAL-12.5 | Enclosed sub-floor spaces - no special requirements for materials, except within 400mm of the ground. No special requirements for framing or supports. Decking to be non-combustible or bushfire resistant within 300mm horizontally and 400mm vertically from a glazed element. |
| BAL-19 | Enclosed sub-floor spaces - no special requirements for materials, except within 400mm of the ground. No special requirements for framing or supports. Decking to be non-combustible or bushfire resistant within 300mm horizontally and 400mm vertically from a glazed element. |
| BAL-29 | Enclosed sub-floor space or non-combustible or bushfire-resistant timber supports. Decking must be non-combustible. |
| BAL-40 | Enclosed sub-floor space or non-combustible supports. Decking must be non-combustible. |
| BAL-FZ | Enclosed sub-floor space or non-combustible supports. Decking to have no gaps and be non-combustible |
| Source: A guide to building in Victoria after the bushfires, accessed 19/11/2015 | |
It is worth noting that freestanding decks in particular are not typically required to comply with the code provided that they are:
- At least 6m away from the main building (Class 1) or any structure attached to it and
- Classified as a Class 10 structure.
As with anything to do with construction and fire ratings, make sure you get confirmation from your local building authority if you are planning on building a free-standing deck.
How BAL affects pergolas
The type of pergola you have will determine what regulations apply to your pergola – an open roofed pergola for example would have a hard time complying with roofing regulations. Local council advice should be sought out for information on the specifics of your pergola design to ensure compliance with the code. Pergolas may be exempt from the code provided they are:
- At least 6m away from the main building (Class 1) or any structure attached to it and
- Classified as a Class 10 structure.
