Glossary
Compartmentation.
The use of fire-resisting walls, floors, doors and fire-stopping to divide a building into compartments that contain a fire to its origin for a defined period of time. The structural foundation of the stay-put strategy in UK residential blocks of flats.
How compartmentation works.
A compartment is a part of a building bounded by fire-resisting construction. Walls, floors, ceilings and doors that form the compartment boundary are designed and constructed to resist fire spread for a specified period (typically 30, 60, 90 or 120 minutes depending on the building type and use). Fire-stopping at penetrations through the compartment boundary (services, ducts, pipes, cables) is part of the compartmentation: a wall rated for 60 minutes performance is only worth 60 minutes if its penetrations are properly sealed.
Why FRAs focus on compartmentation.
Compartmentation in housing is invisible most of the time. It sits behind plasterboard, above ceilings, around services. It can be compromised by refurbishment work that opened up the compartment and was not properly fire-stopped at completion, by services installation over the building's life, or by direct tampering. The FRA is one of the few times the dutyholder gets a structured view of whether compartmentation is intact. For a Type 2 or Type 4 FRA, compartmentation is often the specific concern that drove the deeper scope.