What is a fire door frame?
A fire door frame is the lining the door leaf hangs in, fixed to the surrounding structure. It is part of the tested assembly, and a rated leaf in the wrong frame does not achieve the rating.
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<img src="https://fireoptix.co.uk/glossary/door-frame/diagram.svg" alt="fire door frame — diagram from FireOptix" width="880" height="620" loading="lazy">
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<a href="https://fireoptix.co.uk/glossary/door-frame">What is a fire door frame?</a> — diagram by
<a href="https://fireoptix.co.uk">FireOptix</a>
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</figure>The frame does two jobs: it holds the leaf in the right position, and it carries the seals that close the gap when heat arrives. Both depend on it being fixed properly to the structure, which is why the gap behind the frame is inspected as carefully as the gap around the leaf.
Frames and leaves are tested together. Mixing a leaf from one manufacturer with a frame from another produces an assembly nobody has tested, and the certification that came with each part says nothing about the combination.
Because the frame is fixed and the leaf moves, frames are usually the part that survives a refurbishment while leaves get replaced — which is exactly the situation that creates an untested pairing.
In practice
A frame fixed with two screws where the certification assumed more.
It is solid to push and has been in place for years without trouble.
The assembly was tested as a whole, and the fixings are part of what holds the door in the opening under heat and pressure.
Nothing about the installation is visible once the architrave is on, which is why installation records matter.
What goes wrong in practice
- A new leaf hung in an existing frame from a different system, producing an untested assembly.
- Packing behind the frame missing or combustible, so the fixing fails before the door does.
- Architrave refitted over a gap that was never filled correctly.