What is a compartment wall?
A compartment wall is a fire-resisting wall that divides a building into separate compartments. To work, it must be continuous from structural floor to structural floor, including through any ceiling void.
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<img src="https://fireoptix.co.uk/glossary/compartment-wall/diagram.svg" alt="compartment wall — diagram from FireOptix" width="880" height="620" loading="lazy">
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<a href="https://fireoptix.co.uk/glossary/compartment-wall">What is a compartment wall?</a> — diagram by
<a href="https://fireoptix.co.uk">FireOptix</a>
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</figure>Continuity is the whole requirement. A wall that stops at the suspended ceiling leaves a connected void above it, and fire and smoke travel through that void into the compartment the wall was built to protect.
Every opening in it — doors, ducts, cables, pipes — is a deliberate weakness that has to be closed with something tested for the purpose. That is what makes the wall a system rather than a piece of construction.
Because most of a compartment wall is hidden inside the building, its condition is a matter of record rather than observation. Knowing where the compartment lines run is the first thing a building needs before anyone can check whether they are intact.
In practice
A wall that stops at the suspended ceiling.
It was built that way during a refurbishment, by a contractor following a drawing that showed a partition rather than a compartment wall.
A compartment wall runs to the structural floor above, and one that stops at the tiles divides the room and nothing else.
It is found by lifting a tile, which nobody does on a walk-round.
What goes wrong in practice
- Walls stopping at ceiling level, with the void above left open across the line.
- Compartment lines not marked anywhere, so contractors drill through them without knowing.
- Openings formed for new services and made good with the wrong material.