Traditionally a 20 minute fire doorset comprised a 25mm doorstop, no intumescent and a 30 minute blank, is this still acceptable?
Prior to 1972 the British Standards prescriptively defined how to construct a fire doorset and this included using 25mm doorstops. Since then the standards have been changed and the method of proving performance is by independent testing. For economic reasons, manufacturers generally test to achieve 30 minutes and sell the same product for 20 minute applications. Unless there is specific test evidence, 20 minute fire doorsets still require the intumescent strips tested for 30 minutes to be fitted. Purchasers should satisfy themselves that acceptable evidence exists, rather than working to out of date prescriptive solutions.
