Bushfire attack level (BAL) ratings: what each level means for a house build

A bushfire attack level (BAL) rating is one of six construction levels in Australia's standard for building in bushfire-prone areas, AS 3959:2018. It reflects the level of bushfire exposure a building could face and helps determine which parts of the house must resist embers, radiant heat or flame¹.

The levels are BAL-LOW, BAL-12.5, BAL-19, BAL-29, BAL-40 and BAL-FZ. The number in each rating shows the upper level of radiant heat, measured in kilowatts per square metre (kW/m²), for that BAL band.² BAL-FZ, the flame zone, has no upper limit and covers exposure above 40 kW/m² with a significantly higher likelihood of flame contact from the fire front¹.

BAL-12.5 is the lowest construction level covered by AS 3959:2018³. At this level, burning debris is the main threat and radiant heat stays at or below 12.5 kW/m².¹ The construction requirements cover ember protection and the build-up of debris. BAL-LOW applies where the building is far enough from the vegetation that no specific bushfire construction requirements apply under the standard, although burning debris can still reach it.

Under the National Construction Code 2022, a house, or a deck or outbuilding, in a designated bushfire prone area must be designed and constructed to reduce the risk of ignition from embers, radiant heat or flame, based on the level of bushfire exposure⁴.

Each BAL level changes how much protection different parts of a building need against embers, radiant heat and flame. The requirements become more demanding as the BAL level increases, from ember protection at BAL-12.5 to higher radiant heat at BAL-19 and BAL-29 and to radiant heat with possible flame contact at BAL-40 and BAL-FZ¹.

In Victoria, the Victorian Building Authority describes the minimum BAL-12.5 construction as sealing roofs and gaps around doors and windows, and screening windows, to reduce ember attack².

CSIRO's bushfire best practice guide shows that window and door requirements also become stricter at higher BAL levels. It summarises standard glass and suitable timber or non-combustible frames at BAL-12.5, toughened glass at BAL-29, fire-rated glass at BAL-40 and non-combustible windows with shutters at BAL-FZ. The guide also recommends metal mesh screens with openings of less than 2 mm for openable windows, and screened protection for external doors⁵.

BAL-FZ, or the flame zone, has its own construction requirements under AS 3959. In New South Wales the code applies the standard except for that section, so a BAL-FZ house is built to the specific conditions of its development consent⁴. Where a setback of at least 10 m between the building and the hazard cannot be provided, AS 3959:2018 requires all building elements to be tested to a specified bushfire testing standard³.

The National Construction Code also requires vehicle access to the site for firefighting and access to a sufficient water supply⁴.

In New South Wales, where mains water is not provided or cannot be guaranteed, Planning for Bush Fire Protection 2019 sets a static supply per lot¹. Three volumes apply by lot size: 5,000 L for a residential lot of less than 1,000 m², 10,000 L for a rural-residential lot of 1,000 to 10,000 m², and 20,000 L for a lot of more than 10,000 m².

No official data exists on what each BAL level adds to the cost of a new house. Planning Victoria states that a home in a bushfire prone area may cost more because of the additional materials and labour required to address bushfire safety, and that the difference varies with the builder, the size and design of the home and the BAL level⁶.

In New South Wales, a development application on bush fire prone land is accompanied by a bush fire assessment report showing how the proposal meets the state's bushfire planning requirements³. A complying development certificate needs a BAL certificate instead, from the council or a consultant recognised by the Rural Fire Service¹⁷.

Official fees apply to the assessment or certificate process, rather than to the BAL level itself. The NSW Rural Fire Service does not charge for development applications for new single dwellings, sheds or alterations and additions to existing dwellings¹⁷. Council BAL certificate fees vary. As one example, Nambucca Valley Council charges $520.00 in 2026–27.¹⁸ The fee does not apply where the certificate is linked to a complying development application lodged with the council for assessment.

In Victoria, a property vendor statement must state whether the land is in a designated bushfire prone area⁶.

A landowner can apply to the Building Appeals Board for a decision on whether the additional bushfire construction requirements apply to the lot. Planning Victoria listed the fee at $124.60 for a dwelling in its guide, last updated 1 July 2024, with processing taking up to 12 weeks⁶.

Estate documents can carry bushfire paperwork before any assessment is ordered. Among the 38 estates in BuildStreet's July 2026 review of published estate documents, three publish bushfire documents or bushfire clauses alongside their design guidelines¹⁹. This does not mean only three estates had bushfire requirements, because the review counted only documents that were publicly available.

Flagstone in Logan lists bushfire requirements by stage on its buying-and-building page, including a bushfire management plan for stages 8 to 14 and a BAL contour map¹⁹. Everleigh's owner portal lists a bushfire management plan among the documents it holds²⁰. Foreshore Coomera's development code requires the siting and design of buildings, structures and landscaping to comply with an approved bushfire management plan that is not published with the guidelines²¹.

The bushfire status of a block is found first through the relevant state or council map, then through the property's own assessment or certificate.

In New South Wales, the Rural Fire Service's online tool locates an address on the councils' bush fire prone land. The result is only valid on the day of the search, while the council's planning certificate confirms the bushfire status for the property⁷.

In Victoria, a VicPlan property report states whether a property is in a bushfire prone area or covered by the Bushfire Management Overlay².

In Queensland, the state mapping is published as an open dataset. Local council planning maps can also show areas designated as bushfire prone²².

The map shows whether the land is bushfire prone, while the BAL comes from a site assessment against AS 3959.² A block can sit inside a mapped area and still be assessed as BAL-LOW where the building is far enough from the vegetation.¹ In Victoria, a new home in a designated bushfire prone area must still be built to at least BAL-12.5, even where the assessment returns BAL-LOW².