If your hinterland block sits inside a designated bushfire prone area, the house has to be built to AS 3959 Construction of buildings in bushfire-prone areas, and how much that changes your build comes down to one number: the Bushfire Attack Level, or BAL, assessed for your specific site. The National Construction Code sets this out plainly. For a house, NCC 2022 Volume Two Performance Requirement H7P5 applies to a Class 1 building, and to a Class 10a building or deck associated with it, constructed in a designated bushfire prone area. Clause H7D4 is the Deemed-to-Satisfy route to that Performance Requirement, and it lets you get there by building in accordance with AS 3959 or the NASH Standard for steel framed construction in bushfire areas — with one significant carve-out we cover below. H7P5 goes further than materials: it also requires vehicular access to the site to assist firefighting and emergency personnel defend the building or evacuate occupants, and access at all times to a sufficient supply of water for firefighting purposes on the site. In Tanawha, Mons, Forest Glen, Kiels Mountain and Diddillibah, those last two requirements often bite harder than the cladding does.
What “bushfire prone area” actually means in Queensland
Two separate systems are at work here, and people mix them up constantly.
The first is planning. Local governments map bushfire hazard through their planning schemes, and a development application over a mapped site is assessed against the relevant overlay code. The Sunshine Coast Planning Scheme 2014 carries its overlay codes in Part 8, which Council describes as containing the overlay codes for the 13 overlays mapped in Schedule 2. Noosa Shire Council maps its own overlays through the Noosa Plan 2020, and Council’s mapping page describes overlay maps as indicating where a particular hazard or value might influence how or where development can be carried out. Because the published overlay map categories differ between the two councils, confirm the bushfire designation for your specific address with the relevant council rather than assuming it works the same way on both sides of the shire boundary.
The second is building. Business Queensland is explicit that a planning scheme can include the designation of bushfire-prone areas for the National Construction Code, but it cannot include fire safety standards for buildings constructed in bushfire-prone areas, or matters about the construction of buildings including building orientation, boundary clearance requirements and distances of buildings or structures from vegetation to address a bushfire hazard. Those are building matters, dealt with under the building assessment provisions.
So council mapping decides whether AS 3959 applies to you, and AS 3959 decides what you actually have to build. Your building certifier, not your town planner, signs off on the BAL construction. Read this alongside our guide to building approvals on the Sunshine Coast and in Noosa, because the two approvals run on different clocks.
How a BAL is worked out for your site
AS 3959-2018 sets out a simplified procedure built on a few inputs: the classification of the vegetation near the building, the distance from the building to that vegetation, the effective slope of the ground under that vegetation, and the fire weather severity applicable to the region. Downslope vegetation is the one that catches hinterland owners out. Fire runs uphill, so a house near the head of a gully at Kiels Mountain, or on the eastern fall at Mons, can carry a higher BAL than a flat block the same distance from the same trees.
Neither AS 3959 nor the NCC clauses above name who must perform the determination. In practice your building certifier either determines the BAL or accepts a written BAL report from a suitably qualified bushfire assessor, so confirm with the certifier which they want before you commission anything. Get it done before working drawings, not after, because the BAL drives window selection, cladding, decking, subfloor treatment and roof detailing. On a sloping, vegetated block it also interacts with the structural design, which we cover in building on a sloping block in Queensland.
BAL ratings and what each level means for the build
The table below summarises the six levels in AS 3959-2018 and what each one does to a house. It is a summary for planning purposes; the standard itself governs, and your assessor and certifier have the final say.
| BAL rating | Radiant heat exposure (AS 3959-2018) | Main threat | What changes in the build |
|---|---|---|---|
| BAL—LOW | Risk considered insufficient to warrant specific construction requirements | Negligible | No AS 3959 construction requirements. The site can still sit inside the mapped overlay, so the assessment still has to be done and evidenced to the certifier. |
| BAL—12.5 | Up to 12.5 kW/m² | Ember attack | AS 3959 Section 5. Ember-proofing throughout: gaps sealed, vents and weepholes screened with mesh no coarser than 2 mm aperture in corrosion-resistant steel, bronze or aluminium; Grade A safety glass to low-level glazing; subfloor enclosed or screened; roof sarked and penetrations sealed. |
| BAL—19 | Above 12.5 and up to 19 kW/m² | Embers plus increasing radiant heat | AS 3959 Section 6. Everything above, plus toughened Grade A safety glazing to exposed panes, screens to openable windows, and restrictions on external wall and decking materials close to the building. |
| BAL—29 | Above 19 and up to 29 kW/m² | Heavy ember attack and significant radiant heat | AS 3959 Section 7. External walls non-combustible or bushfire-resisting timber, heavier toughened glazing, metal-framed screens, bushfire-resisting or non-combustible decking, and tighter eave and roof detailing. This is where product choice starts narrowing noticeably. |
| BAL—40 | Above 29 and up to 40 kW/m² | Radiant heat with increasing likelihood of direct flame contact | AS 3959 Section 8. Non-combustible external walls or systems tested to AS 1530.8.1, bushfire shutters or heavy toughened glazing behind screens, non-combustible decking and roof, no unprotected openings. Windows and doors become a specialist package. |
| BAL—FZ (Flame Zone) | More than 40 kW/m² | Direct exposure to flame | AS 3959 Section 9 covers BAL—FZ, but NCC 2022 clause H7D4 excludes Section 9 from the Deemed-to-Satisfy pathway, and excludes BAL—FZ buildings from the NASH pathway too. A BAL—FZ house therefore has to be dealt with as a Performance Solution against H7P5, agreed with your building certifier. Wall, window, door and roof systems are typically tested to AS 1530.8.2, and standard residential windows and doors generally will not do. |
That carve-out is the detail most people miss. Up to and including BAL—40 you have a straightforward Deemed-to-Satisfy path: build to AS 3959 or the NASH Standard and the certifier can approve it on that basis. At BAL—FZ that path is closed by H7D4 itself, so you are into a Performance Solution, and the design, evidence and certifier engagement all have to start earlier.
The step that changes the cost structure most is between BAL—29 and BAL—40. Below BAL—29 you are largely detailing and screening a conventional house with conventional trades. From BAL—40 you are buying tested systems, and substitution stops being an option, because the certifier needs test evidence for the exact system installed rather than something similar.
What this means in Tanawha, Mons, Forest Glen, Kiels Mountain and Diddillibah
These are inland suburbs, not coastal ones, and they behave differently. Blocks are generally larger, often acreage, with retained vegetation on or beside the site, gully systems, and real slope. That combination is exactly what AS 3959 is designed around, so a hinterland block is far more likely to return a meaningful BAL than a serviced lot in a coastal estate.
Two things follow. First, separation is usually your cheapest control. Because the BAL is driven by distance to classified vegetation and the effective slope beneath it, where you place the house on the block can move you down a band before you have spent a dollar on shutters or tested glazing. That is a siting conversation for concept stage, not tender.
Second, the H7P5 requirements for vehicular access and on-site water are not paperwork. A long private driveway off a hinterland road has to be usable by a fire appliance, and on an unsewered acreage block the on-site firefighting water supply has to be planned into the tank strategy rather than bolted on afterwards. On hinterland sites such as our Elouera Drive project at Ninderry, driveway grade, turning and services are design constraints from day one.
How to check whether your block is affected
- Pull the council mapping. For Sunshine Coast Council, the Development.i site report returns planning scheme zoning and overlay information for an individual property. For Noosa Shire, start with the Noosa Plan 2020 mapping and confirm the bushfire designation for your address directly with Noosa Shire Council.
- Ask your building certifier how they want the BAL determined once you have a rough building footprint. Move the footprint and the answer can change.
- Give the determination to your designer before working drawings. Windows, doors, cladding, decking and the subfloor all flow from it.
- Confirm the certifier’s evidence requirements for tested systems at BAL—40, and the Performance Solution pathway at BAL—FZ, before anything is ordered.
Where the cost actually sits
We will not quote a BAL surcharge, because there is no honest single figure. The driver is which parts of the envelope have to change and how much of the building is exposed. What consistently moves the number is glazing (screening, then toughened glass, then shutters or tested window systems), external wall and soffit materials, decking, subfloor enclosure, roof sarking and penetration detailing, and on hinterland blocks the access and water infrastructure. Glazing facing the vegetated side of the block is where cost tends to concentrate at BAL—40 and above, because every exposed pane has to be screened, upgraded or replaced with a tested assembly. Our guide to the cost to build a house on the Sunshine Coast shows where those items sit in a full budget. Price the bushfire package as a named allowance rather than letting it hide inside a provisional sum.
Whoever you engage, check they are licensed for the work first — our guide on how to check a QBCC licence takes two minutes. If you are planning a hinterland home, see how we approach new home builds on the Sunshine Coast, or call Tom Roebuck on 0477 333 386. Roebuck Concepts holds QBCC licence 15280811 and works across the Sunshine Coast and Noosa Shire from Coolum Beach.
Frequently asked questions
Does a bushfire overlay automatically mean I have a BAL to build to?
Not necessarily. The overlay triggers the assessment, but the assessment can still return BAL—LOW, which AS 3959-2018 treats as a risk insufficient to warrant specific construction requirements. You still need the determination on file for your certifier.
Can council tell me how far my house must be from the trees?
No. Business Queensland states that a planning scheme cannot include matters about the construction of buildings, including building orientation, boundary clearance requirements and distances of buildings or structures from vegetation, to address a bushfire hazard. Separation distance feeds into the AS 3959 assessment, which is a building matter for your certifier.
Do sheds, carports and decks have to comply?
NCC 2022 clause H7D4 applies to a Class 1 building, and to a Class 10a building or deck associated with a Class 1 building, in a designated bushfire prone area, so an attached deck or an associated garage is in scope. Confirm the extent structure by structure with your certifier.
What about units, townhouses or duplexes?
It depends on the classification, not the marketing name. A duplex, and many townhouses, are Class 1a where each dwelling is separated by a fire-resisting wall and there is no dwelling above or below another, so they sit under Volume Two clause H7D4 like any other house. Where dwellings are stacked, the building is Class 2, and NCC Volume One Part G5 applies: clause G5D3 requires a Class 2 or 3 building, and a Class 10a building or deck immediately adjacent or connected to it, to comply with AS 3959. Part G5 also picks up Class 9a health-care buildings, Class 9b early childhood centres and schools, Class 9c residential care buildings, and Class 4 parts associated with those buildings. Performance Requirement G5P1 sets the design bushfire at an annual exceedance probability of not more than 1 in 100 years, or 1 in 200 years for a Class 9 building. Get the classification confirmed by your certifier before you assume which volume you are in.
Can I lower my BAL by clearing vegetation?
Sometimes, but clearing is regulated separately under council vegetation provisions and state law, and there is no point counting on the removal of vegetation you are not lawfully permitted to remove and keep removed. Treat siting, not clearing, as your first lever.
Does a BAL change how I should choose a builder?
It should. At BAL—29 and above the build depends on correct detailing and on evidence for tested systems, which is documentation work as much as trade work, and at BAL—FZ it involves a Performance Solution rather than a straight Deemed-to-Satisfy approval. Our guide on how to choose a builder in Queensland covers the questions worth asking.