AS 1530.4 — Fire-Resistance Tests of Building Elements

What AS 1530.4 measures

The test subjects an element to the standard time-temperature curve inside a furnace and records how long it continues to perform. The result is expressed as a Fire Resistance Level with three components: structural adequacy (ability to carry load), integrity (ability to stop flames and hot gases passing), and insulation (ability to limit heat transfer to the unexposed face). A dash replaces a criterion that does not apply — for a non-loadbearing partition the structural component is written as -, giving -/60/60 for a 60-minute wall.

Failure criteria

Integrity fails if a cotton pad placed against the unexposed face ignites, if a 6 mm gap gauge can pass through a crack and be moved 150 mm, if a 25 mm gap gauge passes fully through, or if sustained flaming appears. Insulation fails when the average temperature on the unexposed face rises more than 140 K, or when any single thermocouple rises more than 180 K, above the initial reading.

Where projects go wrong

In practice the element rarely burns through. It bends. Steel and timber sections heat at different rates on the two faces, develop curvature and open a gap at exactly the point where the specimen is least restrained — usually the top corners, the lock side or the threshold. Most failures we see are integrity failures at one of those three locations, not a material that could not withstand the heat.

At a glance

• Reported as FRL: structural adequacy / integrity / insulation
• Non-loadbearing elements use a dash for structural adequacy
• Insulation limit: 140 K average, 180 K maximum rise
• Common ratings: 30, 60, 90, 120 and 240 minutes

Common questions