Fire-Isolated Stairways and Ramps under BCA Part D1: Clause D1.3

AUST Hendry building surveying consultants advise that the Building Code of Australia, in Part D1 Provision for Escape contains clause D1.3 – When fire-isolated stairways and fire isolated ramps are required. This article provides an explanation for designers of the requirements of this clause.

What options are available when a stair connects three storeys in a Class 5 building?

  1. Provide a fire-isolated stair
  2. Where sprinklers are installed, a non-fire-isolated stair can be provided
  3. Provide a non-fire-isolated stair, provided that only two floors are served.

The illustration below depicts exits in a Class 5 building. As illustrated, D1.3 (b)(iii) does not allow a non-fire-isolated stair to directly connect three storeys unless the Class 5 building has a sprinkler protection system. However, the stair can pass through or pass by a third storey provided it does not provide access to or egress for and is separate to the additional storey.

In this example, the basement stair flight (part B) has a 60 minute FRL separation from part A stair 1. The remaining section of the stair connects ground and level 1 only. Stair 2 connects basement and ground floor only. Therefore both stairs will comply with D1.3. The separating construction between parts A and B of stair 1 must have no opening that could permit the passage of fire or smoke.

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