AUST – HENDRY building surveyors advise that the Building Code of Australia (BCA) in Part C3 Protection of Openings contains Clause C3.8 Openings in fire isolated exits. Designers must be aware of the provisions relative to windows in fire stairs.
Building Code of Australia: Clause 3.8 – Issue
Is it possible to construct a window in a fire stair that is exposed to the lower roof of a building that does not have a fire resistance level?
Building Code of Australia: Clause 3.8 – Explanation
C3.8 (b) only addresses windows in fire stairs that are exposed to other openings in a wall of the same building. No exposure exists between the openings in the fire stair itself. The windows in a fire stair overlook a roof which does not have an FRL. The building however must be sprinkler-protected to AS 2118.1, as AS 2118.4 does not apply to residential buildings over four storeys.
Considerations: No deemed to satisfy provision exists in the BCA to specifically deal with the issue identified. Consideration must therefore be given to the effectiveness of the sprinkler system, the actual roof construction and whether performance requirements CP2 and DP5 are satisfied. The openings may be acceptable where the sprinkler system complies with AS 2118.1 and a fire rated plasterboard lining is provided on the underside of the lower roof.
The following illustration from BCA Illustrated depicts a cross section of a multi storey building with windows in a fire isolated stair exposed to the lower roof of a building: BCA Illustrated
BCA Illustrated contains104 illustrations (each containing an issue, explanation, references and an illustration) in Part C3 – Protection of Openings
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