Construction of escape stairs

The flights and landings of escape stairs should be constructed of materials achieving class A2-s3, d2 or better in all of the following situations. a. If the escape stair is the only stair in a building with more than three storeys. b. If the escape stair is within a basement storey. c. If the escape stair serves any storey that has a floor level more than 18m above ground or access level. d. If the escape stair is an external escape stair, except where the stair connects the ground storey or ground level with a floor or flat roof a maximum of 6m above or below ground level. e. If the escape stair is a firefighting stair. Materials achieving class B-s3, d2 or worse may be added to the top horizontal surface, except on firefighting stairs