RISF stands for Resistance to the Incipient Spread of Fire. It refers to a ceiling membrane’s ability to limit the temperature rise in the ceiling cavity to prevent fire from spreading through the void above the ceiling.
RISF is an additional requirement to basic fire resistance (FRL) , as it considers the insulation of the entire ceiling space — not just the exposed face.
A standard FRL insulation criterion only measures temperature rise on the unexposed face of the ceiling membrane itself. RISF goes further — it requires that the temperature of materials within the ceiling cavity (timber joists, wiring, insulation) remains low enough that they will not ignite and allow fire to spread rapidly through the void.
The NCC requires 60 minutes of RISF for ceiling membranes that form the primary fire barrier between occupancies and a shared ceiling or roof void. The most common scenario is Class 2 apartment buildings where the separating walls between units terminate at the ceiling line rather than extending to the underside of the roof — making the ceiling the only barrier preventing fire from bypassing the inter-tenancy walls via the roof space. Any installation in a determined RISF ceiling, including a downlight, must maintain the RISF performance, not just the FRL.
The AT9012 FR does not carry an RISF rating. It is therefore potentially not suitable for installation in top-floor apartments where a shared roof cavity exists between inter-tenancy residences and the ceiling is required to achieve RISF.
For these applications always consult a fire assessor or building certifier to determine whether RISF applies to your ceiling and whether the AT9012 FR is suitable for the intended installation.
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