Costs, Price Factors and 2026 Rules
Bushfire (BAL) and wind ratings for a new roof: what AS 3959 and AS 4055 change about the job and the price
How your site's bushfire attack level and wind classification affect roof and cladding materials, fixings, tie-downs, ember protection and cost in Australia.
Two site ratings can change the specification and price of a new roof more than the choice of material: the bushfire attack level (BAL) under AS 3959 for land in a bushfire-prone area, and the wind classification for housing under AS 4055 (N1 to N6 for non-cyclonic areas and C1 to C4 for cyclonic areas). A higher BAL means ember-proof details, non-combustible sarking and gutters, and restrictions on some materials. A higher wind classification means closer batten and screw spacings, heavier tie-downs and sometimes cyclone-rated products. Ask every roofer which BAL and wind classification they priced for; if quotes assume different ratings they are not comparable.
This guide is part of the roof replacement cost overview. It is general information; the standards and NCC are technical documents and your surveyor or certifier decides compliance.
Bushfire attack levels
AS 3959 Construction of buildings in bushfire-prone areas sets six levels, from lowest to highest exposure:
| BAL | What it broadly means | Roofing implications (general) |
|---|---|---|
| BAL-LOW | Very low risk; no specific construction requirements | Standard roof |
| BAL-12.5 | Ember attack | Seal gaps against ember entry, mesh or seal vents and ridges, non-combustible or suitable sarking |
| BAL-19 | Increasing ember attack and burning debris | As above, with more items required to be non-combustible |
| BAL-29 | Increasing ember attack and radiant heat | Stricter material requirements for roof, gutters, eaves and penetrations |
| BAL-40 | Radiant heat and possible flame contact | Many items must be non-combustible; tested systems may be needed |
| BAL-FZ (flame zone) | Direct flame contact likely | Most restrictive; specialised tested systems |
Your BAL is set by an assessment of vegetation type, distance and slope, usually done by a bushfire consultant or using the method in AS 3959. Your council or state planning authority maps bushfire-prone land. Re-roofing may require the new work to meet the BAL for the site, particularly where a building permit is needed. See council approval.
Ember protection details that cost money
- Sealing the gaps under the roof covering, at ridges and at the fascia, usually with mesh or purpose-made closures with small apertures
- Non-combustible sarking under tiles or steel
- Sealed or metal-meshed vents and skylights
- Gutters and downpipes of non-combustible material, and leaf guards that meet the standard where required
- Steel or other non-combustible flashings and valleys
Wind classifications
AS 4055 Wind loads for housing classifies house sites by region, terrain, shielding and topography:
- Non-cyclonic: N1 (lowest) to N6.
- Cyclonic: C1 to C4, in regions that include much of coastal northern Queensland, northern Western Australia and the Northern Territory.
A suburban site well shielded by other houses may be N2, while a house on a hilltop or near the coast can be N3 or higher. The classification sets the design wind speed that the roof, battens, fixings and tie-downs must resist.
What a higher wind class changes
- Batten size and spacing. Closer spacing means more battens and more labour.
- Screw and clip spacing. More fixings per sheet and sometimes cyclone washers or specific screw types.
- Tie-downs. The connection from roof to walls and walls to floor may need upgrading, especially when replacing heavy tiles with light steel.
- Products. Some sheet profiles and tile fixings are only rated up to certain classes.
- Engineering. In cyclonic areas, an engineer's certification is commonly needed.
Worked example: rating-driven cost differences (illustrative)
Two identical 200 m² houses get tile-to-steel quotes.
| Item | House A: BAL-LOW, N2 | House B: BAL-29, N3 |
|---|---|---|
| Base re-roof at $120 per m² | 200 × 120 = $24,000 | 200 × 120 = $24,000 |
| Extra battens and fixings | $0 | $1,800 |
| Ember sealing, mesh, non-combustible sarking | $0 | $2,600 |
| Upgraded tie-downs and engineer's letter | $0 | $2,200 |
| Compliant gutters and leaf guard | Included standard | $1,400 extra |
| Fixed costs | $4,500 | $4,500 |
| Total | $28,500 | $36,500 |
House B costs $8,000 more for the same size and material, or $40 per m². The extras are illustrative but the pattern is real: ratings add line items. Enter your own figures in the re-roof cost estimator as extra fixed costs.
How to find your ratings
- Bushfire-prone land. Check your state's bushfire-prone area map (for example, the NSW Planning Portal, VicPlan in Victoria, or your council). If the land is mapped, get a BAL assessment.
- Wind classification. Ask a building certifier, surveyor or engineer, or the roofer's supplier. In Queensland and cyclonic regions, councils often publish guidance.
- Existing house records. Original building approval plans may state the BAL and wind class, but older approvals pre-date current standards.
Questions to ask each roofer
- What BAL and wind classification have you priced for, and how did you determine them?
- Which items in the quote are there because of those ratings?
- Do the products have documentation showing they meet AS 3959 for my BAL?
- Will you upgrade tie-downs, and will an engineer or certifier sign off?
- Is any approval needed because of the bushfire rating?
Frequently asked questions
Does a steel roof make my house bushfire-safe?
No single product makes a house safe. The roof is one part of a system that includes gutters, eaves, vents, windows, walls and the garden. Ember entry through gaps is a major cause of house loss, which is why detailing matters.
Will a better-rated roof lower my insurance premium?
Some insurers consider construction features in pricing, but premiums depend on many factors. Ask your insurer directly; do not assume a discount.
Can I keep my tiles in a high BAL area?
Tiles can be used at various BALs if the sarking, sealing and other details meet the standard. Ask your certifier which details apply.
What if my house was built before bushfire rules applied?
Existing houses are not generally required to be upgraded, but new building work may need to meet current requirements. Ask whether your re-roof triggers that.
Sources
- Standards Australia — AS 3959 bushfire construction and AS 4055 wind loads for housing
- Australian Building Codes Board — National Construction Code bushfire and structural provisions
- NSW Planning Portal — bushfire-prone land mapping in NSW
- Queensland Building and Construction Commission — guidance for building in cyclone and storm regions
- Planning Victoria — Victorian planning maps and bushfire overlays
