Building a House in a Bushfire Zone

One of the first questions I ask, either to the land sales agent or the client (or even of myself when I am standing on a block of land) is: Is this block of land affected by potential Bush Fire Attack?

I did this the other day when I was standing with a client in a newly established subdivision out in Moggill, which is a suburb of Brisbane about 20 kilometers west of the city. It was the nice block of land. It was large, and it had a great aspect, but I checked it out with the Brisbane City Council and prior to the subdivision that parcel of land was designated within a BAL 19 Rating for Bushfire Hazard.

As it turned out we spoke to the developer and the new land subdivision had been re-zoned to include a new bushfire zoning overlay and my client’s block was no longer in a BAL rated zone. That was because a large corridor of trees had been cleared as part of the development. However, the block next door was still BAL Rated at 12.5. So that was great for my client but not so good for the people buying the blocks that were clearly exposed to the bush.

So what does all this mean for you?

Building a House in a Bushfire ZoneIf you are thinking of buying a block of land and it doesn’t matter whether it is in a close city environment or in the hinterland, you have to ask the question: Is the building site affected by a Bushfire Attack Level? And don’t fool yourself about an existing property close to the city. I was looking at a knockdown and rebuild project in Camp Hill which backs onto the White Hill Forest Reserve and you guessed it, the land was in a Brisbane City Council Bushfire Hazard Overlay Zone. That’s only 8km from the Brisbane CBD. There are suburbs in the Inner West and North West of Brisbane that are even closer to the city which can also affected.

You must know what the questions are. Stand on your block and look around: Are you exposed in any way to any natural bush nearby? This will be appealing, and it is. But bear in mind that the Queensland Government and the Local Council will have applied some zoning rules that might impact your block.

So you don’t need to know all the intimate details. You just need to know to ask the question. If your building site is affected by a BAL rating, then you need to know what the rating is. The BAL Zone Rating is what will affect the construction methodology and therefore the cost of building your home.

A Bushfire Attack Level (BAL) is a means of measuring the severity of a building’s potential exposure to ember attack, radiant heat, and direct flame contact. It’s measured in increments of radiant heat (expressed in kilowatts/m2).

A BAL is a basis for establishing the requirements for construction (under the Australian Standard AS 3959-2009 Construction of Buildings in Bushfire Prone Areas), to improve protection of building elements from bushfire attack.

The greater the distance from the fire the lower the heat flux and therefore the construction standard is lower.

Once assessed, your property will be defined by one of six BAL ratings:

  • BAL Low: There is insufficient risk to warrant specific construction requirements
  • BAL 12.5: Ember attack. (BAL 12.5 Construction Requirements)
  • BAL 19: Increasing levels of ember attack and burning debris ignited by windborne embers, together with increasing heat flux. (BAL 19 Construction Requirements)
  • BAL 29: Increasing levels of ember attack and burning debris ignited by windborne embers, together with increasing heat flux. (BAL 29 Construction Requirements)
  • BAL 40: Increasing levels of ember attack and burning debris ignited by windborne embers, together with increasing heat flux and with the increased likelihood of exposure to flames. (BAL 40 Construction Requirements)
  • BAL FZ: Direct exposure to flames from the fire, in addition to heat flux and ember attack. (BAL FZ Construction Requirements)

Building a House in a Bushfire Zone

Where your building is greater than 100 Metres from any classified vegetation the BAL rating will more than likely be BAL–LOW and will not require any special construction requirements.  Where there is a risk or potential that ember attack could affect your home then you will likely fall into one of the BAL Rating Zones.

It would take too long for me to describe the various building and construction requirements for each BAL level. Suffice to say that the average sized home in a BAL 12.5 Zone can generally manage the costs within a sound budget. But in a BAL FZ, you will need a custom designed and built solution that will likely have a budget to take your breath away.

If you are about to buy a block anywhere in Brisbane or South East Queensland and you are not sure if it is BAL rated, drop me an email and I would be happy to check it out for you. Better to find out sooner than later.