Last edited 26 Mar 2018

Compartment floor

The spread of fire can be restricted by sub-dividing buildings into a number of discrete, contained compartments.

Fire compartmentation:

  • Prevents the rapid spread of fire which could trap the occupants of a building.
  • Reduces the likelihood of fires growing and creating a danger to occupants, fire and rescue services, and people in the vicinity of the building.
  • Limits the damage caused to a building and its contents.

A compartment floor is horizontal component that forms part of the enclosure of a fire compartment.

Compartment floors are required to provide a minimum degree of fire resistance as set out in Appendix A of Approved document B2 and Appendix A of Approved document B1 (for dwellinghouses). This fire resistance is generally expressed in terms of the number of minutes of resistance that must be provided. Methods for testing fire resistance are set out in BS 476 Fire tests.

Joints between compartment floors should be fire-stopped to maintain the continuity of resistance; and openings for timber beams, joists, purlins and rafters, and pipes, ducts, conduits or cables that pass through any part of a compartment floor should be kept as few in number as possible, kept as small as practicable; and should be fire-stopped. See Fire stopping for more information.

Additional measures may be needed where an atrium, chute, stair, lift and so on passes through a compartment floor.

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