Bushfire Attack Level FAQ's

Australian Standard AS 3959 Construction of buildings in bushfire-prone areas gives two ways to determine a Bushfire Attack Level (BAL).

Method 1 is the simplified procedure where the assessor classifies the vegetation within 100 metres of the proposed building, measures the slope of the land under that vegetation, and measures the distance between the vegetation and the building. These inputs are applied to tables in the Standard, which use a fixed Fire Danger Index for the region. In Queensland that index is FDI 40. Method 1 is efficient, widely accepted, and cost-effective.

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Method 2 is the detailed procedure. It calculates the expected radiant heat exposure from site-specific inputs such as fuel loads, vegetation height, flame length and local fire weather. It is used where Method 1 does not apply, for example where the land under the vegetation slopes downhill by more than 20 degrees. It is also be used where a more precise assessment justifies a lower BAL. Method 2 takes more time, costs more, and does not always give a lower result. We will advise if your site is likely to benefit from it.

Queensland councils include bushfire hazard mapping in their planning schemes, based on state-wide bushfire prone area mapping. This mapping shows land that could be affected by bushfire. It generally sorts land into potential bushfire intensity categories (very high, high and medium). It also shows a potential impact buffer, which is land near a hazard area that could still be affected by embers, smoke or radiant heat.

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If your property falls within the overlay or the buffer, it is treated as a bushfire prone area. At building approval stage, a new dwelling or extension will need a BAL assessment and must be built to the matching construction requirements in AS 3959. For some types of development, such as subdivision or certain material change of use applications, the council's bushfire overlay code may also apply at planning stage. That can bring extra requirements such as access, water supply and vegetation management.

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The mapping is broad-scale and prepared from desktop data, so it shows potential risk across an area rather than conditions on your lot.

The best place to check is on the State Planning Policy Mapping, here:

https://sppims-dams.dsdilgp.qld.gov.au/spp/?tab=search

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Once you have identified your property, the Bushfire Prone Area layer can be found under Safety and Resilience to Hazards > Natural Hazards Risk and Resilience.

Being in the overlay means an assessment is needed, but the overlay category does not set your BAL. Your BAL is determined by conditions on and around your site: the type of vegetation within 100 metres, the slope of the land beneath it, and its distance from the building. A property mapped as very high potential intensity can receive a low BAL if the hazardous vegetation is far enough away or has been cleared. A property mapped as medium can receive a higher BAL if dense vegetation is close by.

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Where the council's overlay code applies at planning stage, it may set requirements that sit alongside the BAL. Examples include minimum separation distances, firefighting water supply, or access for emergency vehicles. We will identify these early so there are no surprises.

There is no fixed figure. The cost depends on the BAL, the size and design of the building, the materials and window systems chosen, and whether it is a new build or an alteration. As a general guide:

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• BAL-LOW has no additional bushfire construction requirements.

• BAL-12.5 and BAL-19 usually involve modest extra cost. Typical items include ember screening to vents and openings, sealing of gaps, safety glass in certain locations, and some limits on external materials.

• BAL-29 brings noticeably higher requirements, particularly for windows, external doors, decks and cladding.

• BAL-40 and BAL-FZ (Flame Zone) can add significant cost. They may require tested window and door systems, bushfire shutters and non-combustible construction in many areas.

  • For a medium sized house in BAL FZ, you might use Firefly wall and roof wrap ($35k supply only), Bushfire Shutters $30k. ​

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The best time to understand these costs is early in design. A BAL assessment at concept stage lets the building's position, layout, window sizes and materials be chosen with the requirements in mind. That can reduce the BAL or the cost of meeting it. Your builder or a quantity surveyor can price the specific requirements once the design is documented.

AS 3959 classifies vegetation by its structure, meaning its height, density and canopy cover, rather than by species. The main classifications are forest, woodland, shrubland, scrub, mallee/mulga, rainforest and grassland. Each has a different expected fire behaviour, and the classification strongly influences the BAL.

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The assessment covers vegetation within 100 metres of the proposed building, regardless of whose property it sits on. Some vegetation can be excluded from the assessment under the Standard. This includes:

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• small or narrow patches below set size limits

• non-vegetated areas such as roads, driveways, waterways and buildings

• low-threat vegetation, such as maintained lawns, cultivated gardens, orchards, parks, and grassland kept in a minimal fuel condition

An Asset Protection Zone (APZ), or bushfire setback, is the area between your home and the hazardous vegetation. It is kept in a low-fuel condition. Its purpose is to reduce the radiant heat, flame contact and ember attack that can reach the building. The BAL in your report often relies on this area being maintained, so it is an ongoing responsibility, not a one-off clearing exercise.

Generally suitable within an APZ:

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• regularly mown lawn

• driveways, paths, paving and gravel

• swimming pools and water tanks

• low, well-spaced garden plantings

• individual trees with separated canopies and lower branches removed, ideally not overhanging the house

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Generally unsuitable, especially close to the building:

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• dense shrubs and continuous understorey

• accumulated leaf litter and fallen branches

• woodpiles

• combustible mulch beside the house

• stored flammable materials

• any vegetation that creates a continuous path for fire to travel towards the home

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You can only manage vegetation on your own land. Vegetation on a neighbouring property or council reserve is assessed as it exists. Where your report or development approval sets specific APZ conditions, those conditions take precedence over this general guidance.

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In NSW, WA and Victoria sub-divisions cannot allow a new development to be less that BAL 29. Secondary dwelling on the same lot is a different scenario but should also follow the same. This rule is not mandatory in Queensland yet but is being enforced by some councils. 

No, but a water tank may help you protect the home in a bushfire event. Water tanks are required if your project needs to have a Bushfire Management Plan as part of a planning approval. 

We recommend clients contact their local council to discuss the vegetation clearing requirements. Typically vegetation clearing is not allowed until building approval is granted.

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Vegetation may also be protected by the State government and you can find more information on vegetation management and regional ecosystems on the Queensland Government website for environment, land and water.

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Redland City Council - Trees and vegetation protection

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