If you own or are buying a property in a NSW bushfire-prone area, you will almost certainly encounter the term BAL — Bushfire Attack Level. It determines what construction requirements apply to your property and has significant implications for building, renovating, insuring and selling.
What is a BAL?
A Bushfire Attack Level (BAL) is a measure of the potential severity of a building's exposure to ember attack, radiant heat and direct flame contact from a bushfire. It is determined under AS 3959:2018 and used to specify construction requirements for buildings in bushfire-prone areas.
The Six BAL Levels
| BAL Level | Risk | Primary Threat | Key Construction Trigger |
|---|---|---|---|
| BAL-LOW | Insufficient | Embers | No specific AS 3959 requirements |
| BAL-12.5 | Low | Ember attack | Non-combustible sarking, vent covers, gutters |
| BAL-19 | Moderate | Embers + radiant heat | Toughened glazing, screened sub-floor |
| BAL-29 | High | Embers + flames + heat | BAL-rated window/door assemblies |
| BAL-40 | Very High | Flame contact + extreme heat | Masonry/steel construction |
| BAL-FZ | Extreme | Direct flame contact | Specialist engineering — may be prohibited |
How is BAL Determined?
BAL is determined by assessing four factors against AS 3959:2018 Table 2.4: the Fire Danger Index (FDI) for the region, the type of surrounding vegetation, the slope of the land under the vegetation, and the distance from the building to the vegetation.
What Construction Does Your BAL Require?
Each BAL level triggers progressively more stringent construction requirements under AS 3959:2018. At BAL-12.5, the focus is ember protection. At BAL-19, toughened glazing and screened sub-floors are required. At BAL-29, entire window and door assemblies must be BAL-rated. At BAL-40 and above, standard construction methods are inadequate and specialist products and engineering are required.
When Do You Need a Formal BAL Assessment?
A formal BAL assessment by a suitably qualified person is required for any development application in a mapped NSW bushfire-prone area. It is not optional and cannot be replaced by a self-assessment tool. If your property is mapped as bushfire-prone and you are planning any development — new construction, additions, secondary dwellings — you need a formal BAL assessment before lodging your DA.
Start with a Preliminary Check
Before engaging a formal assessor, use the BAL-EZ Self-Assessment Kit to get an indicative result. This helps you understand your likely BAL, brief your designer and budget for construction requirements before spending on a formal assessment.
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