BAL levels explained: BAL-LOW to BAL-FZ
There are six Bushfire Attack Levels. From lowest to highest they are BAL-LOW, BAL-12.5, BAL-19, BAL-29, BAL-40 and BAL-FZ. The number in each name is the radiant heat, in kilowatts per square metre, that a building could face. BAL-FZ, the Flame Zone, is the highest BAL rating and adds direct flame contact.
BAL rating chart
| Level | Radiant heat | Main threat |
|---|---|---|
| BAL-LOW | Very low | Little or none |
| BAL-12.5 | Up to 12.5 kW/m² | Embers |
| BAL-19 | 12.5 to 19 kW/m² | Embers and burning debris |
| BAL-29 | 19 to 29 kW/m² | Heavy ember attack and radiant heat |
| BAL-40 | 29 to 40 kW/m² | Intense heat, possible flame contact |
| BAL-FZ | Above 40 kW/m² | Direct flame contact |
What the number means
A BAL rates how exposed a building could be to a bushfire: to burning embers, to radiant heat and, at the top of the scale, to direct flame. Radiant heat is measured in kilowatts per square metre (kW/m²), and the number in each level's name is the top of the band of radiant heat it covers. The higher the number, the more heat the building could face. A site's level is set by the vegetation near the building, how far away it is, the slope of the ground under it and the regional fire danger: how a BAL is worked out explains each of these.
The six levels
BAL-LOW. The lowest level. There's too little vegetation near the building, or it's far enough away, that the standard sets no bushfire construction requirements. BAL-LOW guide
BAL-12.5. Radiant heat up to 12.5 kW/m². Embers are the main risk, so building to this level is mostly about stopping them getting in. BAL-12.5 guide
BAL-19. Radiant heat from 12.5 up to 19 kW/m². More embers, more heat, and burning debris carried by the wind becomes likely. BAL-19 guide
BAL-29. Radiant heat from 19 up to 29 kW/m². Heavier ember attack, and enough radiant heat to crack ordinary glass and damage some materials. It's the level where costs start to climb noticeably. BAL-29 guide
BAL-40. Radiant heat from 29 up to 40 kW/m², and flames from the fire front may intermittently reach the building. BAL-40 guide
BAL-FZ (Flame Zone). The highest BAL rating. The building is exposed to direct flame from the fire front as well as intense heat and embers. Some states restrict new homes here. BAL-FZ guide
Why the level matters
A BAL determines which construction requirements apply to a building. A higher BAL means stricter requirements, which can add cost, so knowing the likely level early helps with where the building goes, its design and its budget.
Why a site's level can change
A BAL belongs to a building in a particular place, not to a whole lot. It depends on the vegetation around the building, so clearing, regrowth, new planting or a change in how land is managed can change it. Moving the building on the lot changes it too, because the distance to the vegetation changes, and so can the slope that counts. How to lower your BAL goes through this with a worked example.
Seeing the likely level for your site
BAL Buddy gives an indicative level for the building and for each other structure you draw, shows which patch of vegetation sets it, and says how far the building would need to move to reach the next lower level. How to find your BAL covers the steps, and when a formal assessment is needed.
BAL Buddy gives an indicative Bushfire Attack Level (BAL) only. It isn't a determination under any Act, and no council or building surveyor has to accept it. For a BAL you can rely on, use an accredited bushfire practitioner.
Questions people ask
Is BAL-40 the same as the Flame Zone?
No. At BAL-40 flames from the fire front may intermittently contact the building. BAL-FZ is direct exposure to flames, in addition to heat and embers.
What is the highest BAL rating?
BAL-FZ, the Flame Zone. It's for sites where the building would be in direct contact with flames from the fire front. Building there usually needs systems tested for flame contact or a specialist design, and some states restrict new homes at this level.
Is a BAL the same as the fire danger rating on the news?
No. The daily fire danger rating forecasts how dangerous conditions will be on a given day. A BAL is a fixed rating of a building site.
Does a higher BAL mean I can't build?
Not usually. A higher BAL means stricter construction requirements, which can add cost. At the highest level some authorities restrict or discourage building, so it pays to check early.
Is there a BAL rating chart I can use to work out my level?
The chart above shows what each level means, not how a site gets one. The level comes from the vegetation class, distance, slope and fire danger index, through tables in AS 3959. How a BAL is worked out explains the method, and the calculator does the lookup for you.