BAL-40
High-risk Bushfire Attack Level for sites with radiant heat flux up to 40 kW/m squared and increased likelihood of direct flame contact during a fire.
Defined in AS 3959 for sites with predicted radiant heat flux above 29 and up to 40 kW/m squared. Construction must address radiant heat, ember attack, and the likelihood of brief direct flame contact. External walls and decks generally require non-combustible materials or systems specifically tested to withstand BAL-40 exposure. Windows must be steel-framed or otherwise tested, with toughened glass and screened or shuttered openings. Decking timber options are very limited, and many designers default to fibre cement, steel, or aluminium decking systems. Subfloor enclosure is mandatory. For buyers, BAL-40 sites often have long lead times for tested window assemblies and bushfire-rated doors. Coordinate orders with the building surveyor's certification list and obtain product test certificates before delivery.
Values and references on this page are indicative and drawn from common industry sources. Always verify the current AS/NZS standard, manufacturer data sheet or NIAA policy publication before relying on figures for design, specification or compliance work.
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