BAL-12.5: meaning and requirements
BAL-12.5 is the second-lowest Bushfire Attack Level. It means a building could face ember attack and radiant heat of up to 12.5 kilowatts per square metre. Building to BAL-12.5 is mostly about keeping embers out of the house: sealing gaps, screening openings and vents, and using suitable materials near the ground.
What BAL 12.5 means
Embers are the main threat. Burning leaves, bark and twigs carried ahead of a fire can land on or around the house and get into gaps, vents, gutters and under decks. Radiant heat at this level is low enough that ordinary glass and most materials cope, so the requirements focus on stopping embers getting inside or lodging somewhere they can start a fire.
What puts a site at BAL-12.5
A site usually lands here when the nearest vegetation is towards the outer part of the 100 metre assessment area, or when it's a lower-intensity vegetation type such as grassland at a moderate distance. Steep ground falling away from the building under the vegetation pushes the level up, so the same bush at the same distance can give a higher level on a slope.
A BAL determines which construction requirements apply to the building. Your building surveyor or an accredited bushfire practitioner can tell you what they are.
How state rules differ
AS 3959 sets the construction requirements, but each state decides where they apply and adds its own rules. In NSW, a site's BAL is set under Planning for Bush Fire Protection, not AS 3959's tables directly. In Victoria, a BAL-LOW site no longer has to be built to BAL-12.5 since 1 May 2026. See the BAL calculator by state for yours.
What BAL-12.5 costs
For most new homes the extra cost at this level is modest, because the work is mainly mesh, seals and material choices rather than special products. It's far cheaper to include during design than to retrofit. Get your builder to price it from your plans.
Getting to BAL-LOW
Moving the building further from the vegetation that sets the level can drop a site to BAL-LOW. How to lower your BAL explains how, and BAL Buddy shows how far the building would need to move. The next level up is BAL-19.
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
What does BAL 12.5 mean?
It means the building could face ember attack and radiant heat of up to 12.5 kW/m² in a bushfire. Embers are the main risk, so the construction requirements focus on keeping them out.
What are the BAL 12.5 requirements?
In short: a non-combustible roof with sealed junctions and ember guards, fine metal mesh over vents and openable windows, sealed gaps around doors, and suitable materials close to the ground and near decks. The full detail is in AS 3959.
Is BAL 12.5 a good rating?
It's the lowest level that comes with construction requirements, and the extra cost is usually modest. Most sites in or near bushland with some separation from the bush end up here or at BAL-19.
What's the difference between BAL 12.5 and BAL 19?
Small. BAL-19 asks for broadly the same as BAL-12.5, with stricter requirements for some materials, mainly glazing and timber close to the ground or a deck. The bigger jump is to BAL-29.