The 5-Point Fire Door Check Explained (With Tolerances)

Every credible fire door inspection is built around five checks. They take minutes per door, need no special tools beyond a gap gauge, and catch the defects behind most failures. Here is each one, with the tolerances that matter.

1. Certification

Look for a certification label or colour-coded plug, usually on the top edge of the door leaf. It proves the door was manufactured and tested as a fire door. No label does not automatically mean no rating, but it means the rating cannot be evidenced, which for a compliance record is the same problem. Where certification is missing, a specialist assessment decides whether the door can stay.

2. Gaps

The gap between the door leaf and frame should be consistently around 3mm, generally between 2mm and 4mm, at the head and both sides. Under the door, the threshold gap is typically up to 8mm where only fire resistance is needed, and tighter, around 3mm, where smoke control matters. Oversized gaps let hot smoke through long before the door itself fails. A 1p coin is roughly 2mm and a pound coin roughly 3mm, handy for a quick sense check.

3. Seals

Intumescent seals, which expand in heat to close the gap, should run continuously around the frame or door edge, with no breaks, paint damage or sections hanging loose. Combined intumescent and smoke seals add brushes or fins that block cold smoke. Damaged or painted-over seals are among the most common failures, and among the cheapest to fix.

4. Hinges

Three hinges minimum on a fire door, all firmly fixed with no missing or loose screws, no visible wear, and CE or UKCA marked as fire-rated. Uncontrolled leaf drop from worn hinges throws off the gaps everywhere else.

5. Closer

Open the door to about 5 degrees and release it. It should close fully and engage the latch without slamming or sticking. A door that needs a shove to latch will be wedged open within a week in a busy building, and a wedged-open fire door protects nobody.

What to do with failures

Record every failure against the door reference with a photo, then remediate: most gap, seal, hinge and closer defects are repairable in place at a fraction of replacement cost. Our remedial works service prices fixes item by item from your findings, or we can run the whole inspection cycle for you with records included.