What is a BAL rating?
BAL stands for Bushfire Attack Level. It's an Australian Standard rating (AS 3959) that classifies how much radiant heat and ember exposure a building will face in a worst-case bushfire. The higher the BAL, the more bushfire-rated the construction must be — and the more your build costs.
The six BAL levels and their cost impact
| BAL | Risk | Build cost premium (indicative) |
|---|---|---|
| BAL-LOW | Insufficient risk to require special construction. | $0 |
| BAL-12.5 | Ember attack risk. | $5,000–$10,000 |
| BAL-19 | Embers + radiant heat up to 19 kW/m². | $10,000–$20,000 |
| BAL-29 | Embers + radiant heat up to 29 kW/m². | $20,000–$40,000 |
| BAL-40 | Embers + radiant heat up to 40 kW/m² + flame contact possible. | $40,000–$70,000 |
| BAL-FZ (Flame Zone) | Direct flame contact likely. | $70,000–$150,000+ or unfeasible |
Ranges are Adelaide Hills 2026 indicative figures. Your builder's quote will vary by design complexity.
Who assigns the BAL?
A qualified bushfire consultant conducts a site assessment under AS 3959 standards. They consider:
- Vegetation type and density within 100m
- Slope of the land and direction the slope faces
- Effective separation distance from the building to bushland
- Local Fire Danger Index for the council area
Cost of a BAL assessment: $600–$1,500. Worth paying before unconditional offer if buying in a bushfire overlay.
What each BAL requires
- BAL-12.5: sealed roof spaces, fire-rated vents, gutter guards, screened evaporative coolers
- BAL-19: above + bushfire-rated windows in vulnerable elevations, non-combustible decking
- BAL-29: above + fire-rated wall cladding, toughened glass on all elevations facing bush, metal flyscreens
- BAL-40: above + steel framing in vulnerable areas, fire shutters, enhanced wall insulation
- BAL-FZ: the house must withstand direct flame contact — steel, concrete, fire-rated everything
How to check if you'll need a BAL
- Run the address through our Zone Check tool
- Look in the Overlays section for "Hazards (Bushfire ...)" — General, Medium, or High Risk
- Any of these means a BAL assessment will be required for new builds or major extensions
BAL vs the bushfire overlay — what's the difference?
- The overlay is a planning layer that flags land at bushfire risk. It triggers the requirement for a BAL assessment.
- The BAL is the specific rating a consultant assigns to a particular building project on that land.
One overlay-zoned street can have BAL-12.5 properties at one end and BAL-40 properties at the other, depending on vegetation, slope, and defendable space.
Read more
- Bushfire overlay SA explained — full cost breakdown
- Stirling buying guide — the Hills suburb with the most BAL exposure
Will you need a BAL assessment?
The Zone Check tells you whether the address is inside a bushfire overlay — which triggers the BAL requirement.
Open the Zone Check →