Westleigh 2120 · Hornsby Shire
Westleigh Builders: Homes Built to a Bushfire Rating
The bush at the back fence is why you bought here. Build for it.
Westleigh's streets run right up to Berowra Valley National Park. That's the appeal: birdsong, gum trees, no neighbours behind. It also means most new homes and additions here are built to a bushfire attack level, and that rating shapes almost every material choice.
Short answer
How does a bushfire rating change a Westleigh build?
The BAL, typically 12.5 to 29 here, sets the construction standard for glazing, cladding, decks, roofing and ember protection. Higher ratings mean toughened glass, non-combustible or rated materials and sealed gaps. Good siting can lower the rating by moving the house further from the bush. Mid-spec homes in Westleigh cost around $2,200 to $2,650 per m².
Written and reviewed by Oliver Alameri
Licensed builder, NSW Contractor Licence 487805C · Founder, Buildana
Fact-checked
What the BAL numbers mean
A bushfire attack level measures how much ember attack and radiant heat a building could face, based on the vegetation type, the slope and the distance to it. The ratings run from BAL-LOW through 12.5, 19, 29, 40 and flame zone.
Each level sets construction requirements under Australian Standard AS 3959. BAL-12.5 is mostly about keeping embers out: sealed gaps, mesh on vents and weepholes, and suitable roof sarking. BAL-19 tightens glazing and cladding. BAL-29 steps up again, with toughened or thicker glass, non-combustible cladding near ground level and heavier-duty window frames and doors.
Most of Westleigh falls somewhere between 12.5 and 29, though lots right on the reserve edge, where the land drops steeply away into thick bushland and the fire would run uphill toward the house, can rate a good deal higher than their neighbours across the road.
- BAL-12.5: ember protection, sealed gaps, screened openings
- BAL-19: higher-rated glazing and more careful cladding choices
- BAL-29: toughened glass, non-combustible materials low down, stronger frames
- BAL-40 and flame zone: specialist design, and complying development isn't available
Every step up the BAL scale costs money. The site plan can sometimes buy you a step back down.
Using the design to lower the rating
The rating depends on distance. On a deep Westleigh block, placing the house further from the bushland edge can drop it a whole level. Thousands saved on windows alone.
Where the house faces the bush matters too. Putting the garage, laundry and fewer windows on the bushland side, with big glass facing the street or a side courtyard, reduces the exposure where it's highest.
An asset protection zone, a managed area of low fuel between the house and the bush, is often required. Its size and where it sits on your land are part of the bushfire assessment and council's conditions.
Backing onto the bush?
Send me your Westleigh address. I'll check the mapping, look at where the house could sit to reduce the rating, and give you a clear idea of the bushfire construction costs.
0476 300 300Materials that work at BAL-29
Face brick and fibre cement are excellent at higher ratings. Timber cladding is possible only in species or treatments rated for the level. Decks close to the house need non-combustible or appropriately rated materials, with no gaps underneath where leaves and embers collect.
Gutter guards, sealed roof junctions and ember-proof vents matter as much as glass. Maybe more. In bushfire events, plenty of houses go up because embers found a gap, long before any flame front arrived.
The rock under Westleigh is Hawkesbury sandstone. Good for footings, expensive to excavate. We keep excavation to a minimum on sloping blocks.
Approvals and cost
On bushfire-prone land, a DA with Hornsby Council includes a bushfire assessment report, and some developments are referred to the NSW Rural Fire Service. Complying development may be available at lower ratings, but not at BAL-40 or flame zone.
A mid-spec home here costs around $2,200 to $2,650 per square metre on unadjusted Rawlinsons Sydney figures. BAL construction sits on top, varying with the rating, the amount of glazing and the materials chosen. We price it from the bushfire report, not a guess.
Bushfire checks for a Westleigh block
Six things that decide the rating and the construction cost.
- 01
Whether the lot is mapped as bushfire prone land
- 02
Vegetation type and slope on the bushland side
- 03
Distance from the house footprint to the vegetation
- 04
Room for an asset protection zone
- 05
The BAL rating from a bushfire consultant's report
- 06
Whether the rating allows complying development or needs a DA
Building in bushfire-prone Westleigh
How does BAL-29 change the build?
It's a moderate-to-high exposure rating under AS 3959. Expect toughened or thicker glazing, non-combustible materials near ground level, sealed gaps and ember-proof vents.
Can I reduce my BAL rating?
Often, by pulling the footprint back from the bushland or managing an asset protection zone. A bushfire consultant can model options before the design is finalised.
Does bushfire rating stop complying development?
Only at BAL-40 and flame zone. Below those, a certifier can still approve it, provided the drawings satisfy the code and the BAL construction requirements.
Can I use timber cladding in Westleigh?
Possibly, if the species or treatment is rated for your BAL level. At higher ratings, brick, fibre cement or metal are often simpler choices.
Sources and references
Costs are from the Rawlinsons handbook with the local cost index applied; rules and timeframes are checked against the sources below.
Live with the bush. Build for the day it burns.
A Westleigh home designed around its bushfire rating is safer, often cheaper to build and easier to insure. Let's start with your block.