What gap should there be around a fire door?

There is no single figure that applies to every door, which is why we avoid quoting one as though it were law. The acceptable range for a given doorset comes from what that doorset was tested and documented with, together with the manufacturer's installation instructions, and it can differ between products. Inspectors work to those references and to the guidance applicable to the building, not to a universal number.

Our report says the threshold gap is excessive. Is that serious?

It depends on what the door is protecting and what the doorset's documentation supports. Threshold clearance is not treated the same way as perimeter gaps, and where smoke control matters the arrangement at the bottom of the door becomes more significant. We assess it against the doorset and the finding rather than assuming either that it is trivial or that the door must be replaced.

Can a gap that is too large simply be filled or packed out?

Not with whatever is to hand. Where a repair route exists, it needs to be a solution supported by appropriate evidence for that application and fitted as intended. Timber offcuts, expanding foam in the leaf edge and general-purpose fillers used to close a gap are among the things we are most often asked to undo, because they cannot be shown to do anything at all.

The door binds on one side and gaps on the other. What causes that?

Usually the leaf is no longer hanging square. Worn or loose hinges, a dropped leaf, a distorted frame or a frame that has moved with the building all produce this pattern. Correcting the alignment often brings several recorded gap findings back into range at once, which is why we look at hinges and frames before considering the leaf itself.

Do you carry out the inspection that measures the gaps?

Where a formal door-by-door inspection report is required, that is arranged through a specialist fire door inspection contractor. Parsec Fire Doors works from that report, or from an existing report or FRA action list, and carries out the resulting repairs, remedials and replacement. Our own pre-works site assessment confirms the scope and cost of the remedial work and is not a formal inspection report.

Guide

Fire Door Gaps & Clearances: When Remedial Work Is Needed

Gap findings are the single most common entry on the fire door reports we are sent. This page explains how the acceptable range is established for your doors, which gap defects can be corrected, and where a gap points to a problem that new hardware will not solve.

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Why Gaps Are Measured At All

A fire doorset works as a complete assembly. The leaf, the frame, the seals and the hardware were tested together, and the gap around the leaf is part of what makes the seals and the assembly behave as they did in that test. Too large and the arrangement no longer resembles what was tested; too tight and the door binds, stops latching, or is forced and damaged.

That is why inspectors record perimeter and threshold measurements door by door. A gap entry on your report is not an opinion about the door looking untidy — it is a record that the assembly no longer matches the arrangement its evidence relates to.

Where the Acceptable Range Comes From

We are careful not to publish one figure and present it as the legal requirement. The range that applies to a specific doorset comes from its test evidence and the manufacturer's installation instructions, and different products differ. Guidance applicable to the building and the inspector's own reference point also feed into how a finding is worded.

In practice this means the first question on site is not how big the gap is, but which doorset this is and what its documentation supports. Where the doorset can be identified, the remedy follows from that. Where it cannot be identified at all, we set out the options honestly, which may include replacement with a doorset of known specification.

Doorset test evidence and manufacturer instructions take precedence
Perimeter and threshold clearances considered separately
Findings checked on site before works are priced
Repair solutions used only where supported for that application
Doors that cannot be identified flagged rather than assumed
Works recorded against your door references

The Realistic Remedial Routes

Often first

Realignment and hinge work

A dropped or binding leaf commonly produces gap findings on more than one edge. Renewing or refixing hinges and rehanging the leaf frequently brings measurements back into range.

Common

Frame and lining work

Loose, packed or distorted frames and linings can be refixed or made good where the substrate is sound, which is often what actually closes a persistent gap.

Where supported

Tested repair solutions

Purpose-made repair products exist for reducing certain gaps and making good damaged edges. We use them where the evidence supports that application and fit them as intended.

Seals and their housings

Gap findings and seal findings usually travel together. Renewing seals into sound, correctly sized grooves is part of restoring the perimeter arrangement.

Threshold

Bottom-of-door arrangements

Threshold clearance, floor finishes and any specified arrangement at the base of the door assessed together rather than by adjusting the leaf alone.

Sometimes necessary

Leaf or doorset replacement

Where the leaf has been trimmed excessively, the frame is beyond making good, or the required arrangement cannot reasonably be restored, replacement is the more defensible route and we will say so.

Getting Gap Findings Priced

Send us the inspection report or FRA action list you hold and we will price the gap entries line by line against your door references, along with the seal, hinge and closer items usually recorded on the same doors.

Where a finding cannot be resolved by adjustment, we set out what replacement would involve rather than repeating a repair that will fail the next inspection. Our guide to repair or replacement explains how we weigh that up, and frames and liners covers the frame side in more detail.

Gap findings rarely appear on their own.

Fire door repairs & remedials Intumescent & smoke seals Frames & liners Fire door hinges Repair or replacement?Common fire door defects

Frequently Asked Questions

Gap Findings on Your Report?

Send us the report or action list and we will price the gap and clearance entries door by door, telling you plainly which are adjustable and which point to replacement.

Get a Fire Door Quote 07841 613936