If your property falls within a Bushfire Attack Level – Flame Zone (BAL-FZ), you’re dealing with the highest bushfire risk classification in Australia. BAL-FZ properties are likely to face direct flame contact, intense radiant heat over 40kW/m², and significant ember attack. It’s a serious rating that demands the most rigorous construction standards under AS3959:2018.
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What is BAL-FZ?
BAL-FZ is short for Bushfire Attack Level – Flame Zone, the most extreme rating in the BAL system. It indicates a site is expected to be exposed to direct flames, extreme radiant heat, and ember attack during a bushfire. This classification sits above BAL-12.5, BAL-19, BAL-29, and BAL-40, each representing increasing levels of bushfire risk.
Because of this elevated danger, BAL-FZ construction involves a significant departure from standard building methods. Only tested, certified, and non-combustible materials are allowed across key structural elements.
Curious how this figure is actually worked out? See our guide on how to calculate your BAL rating.
BAL-FZ Construction Requirements for South Australian Properties
Subfloor and Flooring
All unenclosed subfloor supports must be made from non-combustible materials like concrete, steel, or masonry. Combustible materials, including bushfire-resisting timber, are not permitted in any part of the support structure. Where subfloors are enclosed, the enclosure must be constructed to meet the same standards as external walls required for BAL-FZ.
BAL-FZ Cladding and External Walls
Wall systems must achieve a fire resistance level (FRL) of at least 30/30/30 and be constructed from tested and certified non-combustible materials. Suitable cladding includes:
- Brick, concrete, or rammed earth
- Pre-cast or in-situ concrete panels
- Fire-rated lightweight external cladding systems tested to AS1530.8.2
Any gaps or joints in the external walls must be sealed to restrict ember penetration, with no openings wider than 3mm.
These cladding standards far exceed those found in lower-risk zones like BAL-19 or BAL-29, reflecting the much greater hazard posed in Flame Zone areas.
BAL-FZ Windows
Windows must be specifically designed and tested for BAL-FZ conditions. Key requirements include:
- Fully metal frames (no timber allowed)
- Minimum 6mm toughened glass or double-glazed assemblies
- Seals to prevent ember entry
- External metal screens or compliant bushfire shutters
All operable windows must be fitted with tightly sealed screens to protect the interior from embers and radiant heat. These are stricter specifications than those found in BAL-12.5 or BAL-40, where bushfire-resistant timber or screening options may be accepted.
BAL-FZ Doors
All external doors must be non-combustible or constructed to meet specific fire performance criteria. Requirements include:
- Solid metal or solid core timber doors with a thickness of at least 35mm (if protected by shutters)
- 6mm or thicker toughened glass for any glazed sections
- Tight-fitting weather strips and seals around the entire frame
- Self-closing mechanisms where necessary
Garage doors must also be non-combustible and sealed on all sides, ensuring no gaps exceed 3mm.
BAL-FZ Roofing Requirements
Roofs in BAL-FZ zones must be constructed to stop embers and radiant heat from entering the building envelope. Requirements include:
- Non-combustible roofing materials with full sarking
- Tiled roofs must be sealed at ridges and valleys
- Vents and openings must be covered with corrosion-resistant mesh (max. 2mm aperture)
- Box gutters must be non-combustible and flashed to prevent gaps
These requirements are significantly stricter than what is required for the other BAL ratings, and ensure all entry points are effectively sealed.
BAL-FZ Decking and Outdoor Areas
Outdoor areas pose a major risk for ember accumulation and flame contact, so bal fz decking must be completely non-combustible. Requirements include:
- Decking must be made from materials such as concrete, metal, or systems tested to AS1530.8.2
- Bushfire-resisting timber is not permitted
- Joists, bearers, and framing must also be non-combustible
- Any space beneath decks must be fully enclosed using non-combustible materials
Balustrades, handrails, and steps must also meet non-combustibility standards, especially if positioned near glazing or other vulnerable surfaces.
Need a BAL assessment for your BAL FZ property? Get a quote from SA’s accredited experts.
Meeting BAL-FZ Standards
Properties with a BAL-FZ rating face the most complex approval processes and construction challenges. However, with the right approach and early-stage guidance, it’s possible to achieve both compliance and design goals.
If you’ve received a BAL-FZ rating, it’s important to work with experienced professionals who understand both the legal framework and practical applications of AS3959. At BFHA, our detailed BAL assessments provide clarity on your specific site’s requirements and outline practical steps to move forward.
From initial site analysis to guidance on material selection, our team supports builders, homeowners, and developers throughout South Australia with reliable, informed bushfire assessments.
To discuss your BAL-FZ project or book an assessment, contact our team on 0426 440 012. With years of hands-on experience, we make even the highest BAL rating manageable—without compromising on safety or design.