Repairs & remedial works
Fire Door Gap Adjustment
Fire Door Gap Adjustment: Fire door gap adjustment is the work needed to bring the gaps between a fire door leaf and its frame, and under the door, back within the tolerance in the door's evidence, typically 2 to 4 mm around the edges.
Excessive gaps are the single most common fire door defect found in inspections. Fire and smoke pass through a 6 mm gap far faster than a 3 mm one, and seals can only close the gap they were designed for. Fixing the gap properly means finding why it opened, whether dropped hinges, a warped leaf, a moved frame or a planed-down edge, and correcting that.
What's included?
- Gap readings at head, hinge side, closing side and threshold
- Hinges re-packed or replaced where the leaf has dropped
- Hardwood lippings fitted to narrow leaves where the evidence allows
- Frame adjustment or re-fixing where the frame has moved
- Threshold gaps corrected or drop seals fitted on smoke control doors
- Final readings recorded for the door's file
When do you need a fire door gap adjustment?
- An inspection has failed doors for excessive or uneven gaps
- A door has been planed down after flooring was changed
- Doors rub on one edge and gape on the other
- Daylight is visible around a closed fire door
What do we check or do on each door?
| Edges | Usually 2–4 mm at head and edges unless the evidence says otherwise. |
|---|---|
| Pairs | Meeting stiles on double doors within tolerance and aligned. |
| Threshold | Under-door gap suited to the door; tighter on smoke control doors. |
| Cause | Dropped hinges, warping or frame movement fixed, not masked. |
How does it work?
Measure
Gaps are measured at several points on every edge.
Diagnose
We identify why the gap has opened.
Correct
Hinges, leaf or frame are corrected using a method the door's evidence supports.
Re-measure
Final gap readings are recorded.
How much do fire door gap adjustments cost?
Hinge re-packing from around £90; lipping and re-hanging up to around £260 per door. Guide range £90–£260 per door, ex VAT. We confirm a fixed price once we know the building, door count and access. See all guide prices.
Which standards and law apply?
- BS 8214:2026
- BS EN 1634-1
- Approved Document B
Regulation 10 applies in England only. Wales, Scotland and Northern Ireland have their own fire safety law; see regulation 10 explained.
Fire Door Gap Adjustment: questions
What gap is allowed around a fire door?
Most guidance and manufacturers' evidence expect gaps of about 2 to 4 mm at the head and edges, with 3 mm as a practical target. The door's own certification or test evidence takes precedence if it states a different figure.
How big can the gap under a fire door be?
It depends on the door's evidence. Doors without smoke control often allow a larger threshold gap, sometimes up to around 8 to 10 mm, while smoke control doors usually need 3 mm or less or a tested drop seal.
Can you fix a big gap with a thicker intumescent strip?
Not as a general rule. Seals are tested for a particular gap; using oversized seals to hide a poor fit is not a reliable repair.
Why do gaps open up over time?
Hinges wear and drop, frames shrink or move, leaves warp, and doors are sometimes planed after flooring changes. Each needs a different repair.
Related services
- Intumescent & Smoke Seal Replacement
- Fire Door Hinges & Ironmongery
- Fire Door Remedial Works
- Fire Door Inspections