Fire door gaps are not just a cosmetic issue. If the gaps around a fire door are too wide, uneven or caused by damage, the door may not perform properly in a fire. A fire door is designed to help resist the spread of fire and smoke, but it only works properly when the door leaf, frame, seals, hinges, closer and gaps all work together.
This guide does not give DIY repair instructions. Fire doors are safety-critical products, and incorrect repairs can reduce their performance. Instead, this page explains what property owners, landlords, managing agents and responsible persons need to know about fire door gaps, inspection, repair options and when to involve a competent professional.
If you are responsible for a block of flats, HMO, workplace, commercial premises or managed building, fire door gaps should be checked as part of fire door maintenance and fire risk management.
Last Updated: 2026
Reviewed By: London Safety Certificate Compliance Team
Key Takeaways
- Measure gaps using feeler gauges or laser measures to ensure they are between 2 mm and 4 mm in width.
- Install or replace intumescent seals for effective smoke and fire prevention.
- Use appropriate tools, such as steel rulers, for precise gap measurement and adjustments.
- Regularly inspect and maintain fire doors to prevent gaps from changing due to wear.
- Consult professionals for repairs to guarantee compliance with safety regulations and optimal performance.
Table of Contents
Quick Answer: How Do You Fix Fire Door Gaps?
Fire door gaps should be fixed by first identifying the cause of the gap and then deciding whether the door can be adjusted, repaired, upgraded or replaced.
Common solutions may include:
- adjusting door alignment
- repairing or replacing hinges
- checking the door closer
- repairing damaged frames
- replacing damaged seals
- fitting suitable threshold or smoke control products where appropriate
- replacing an over-trimmed or damaged door
- replacing an unsuitable frame
- arranging a professional fire door inspection
Do not fill fire door gaps with ordinary filler, foam, draught strips or DIY products unless they are suitable for the specific fire door assembly and supported by manufacturer guidance or competent advice.
Why Fire Door Gaps Matter
Fire doors help protect escape routes, communal areas and compartment lines. Gaps around the door can allow smoke and fire to pass through if the door does not close and seal properly.
Fire door gaps can affect:
- smoke control
- fire resistance
- escape route protection
- compartmentation
- self-closing performance
- compliance evidence
- fire risk assessment findings
- resident, staff and visitor safety
GOV.UK guidance for fire doors explains that fire-resisting doors are important for safeguarding means of escape and that fire doors need to be kept in good working order and good repair.
What Are Acceptable Fire Door Gaps?
There is no safe one-line answer for every fire door because the correct gap can depend on the door set, manufacturer’s instructions, seals, threshold arrangement, certification evidence and the building’s fire strategy.
As a general inspection issue, gaps around a fire door should not be excessive, uneven or large enough to compromise fire and smoke protection. GOV.UK guidance says a door may continue to provide adequate protection where it is undamaged and where gaps between the door and frame are not too large.
A competent fire door inspector will normally consider:
| Area Checked | Why It Matters |
|---|---|
| Top gap | Excessive gaps can affect smoke and fire performance |
| Side gaps | Uneven gaps may show misalignment, hinge wear or frame movement |
| Bottom gap | Can affect smoke control and suitability for the location |
| Meeting edges | Important for double fire doors |
| Frame condition | Damaged frames can affect the whole assembly |
| Seals | Missing or damaged seals may reduce protection |
| Door closer | The door must close correctly into the frame |
| Latch | The door may not perform correctly if it does not latch where required |
Common Causes of Fire Door Gaps
Fire door gaps can form or worsen over time because of:
- hinge wear
- loose fixings
- door warping
- frame movement
- building settlement
- humidity or moisture changes
- poor installation
- over-trimming
- damaged seals
- repeated heavy use
- door closer problems
- impact damage
- unsuitable repairs
- worn thresholds
- changes to flooring
A gap problem is often a sign that the door assembly needs inspection, not just quick filling.
Fire Door Gap at the Bottom
Bottom gaps are one of the most common fire door issues.
A bottom gap may be caused by:
- door leaf being cut too much
- uneven floor level
- missing threshold seal
- incorrect threshold detail
- poor original installation
- worn flooring
- movement in the frame
- unsuitable replacement door
The correct solution depends on the door’s location and purpose. A flat entrance door, communal corridor door, stair door, plant room door and office fire door may not all need the same solution.
Where smoke control is required, the bottom gap may need specific consideration. Do not simply add a standard draught strip or sweep without checking compatibility with the fire door assembly.
Gaps Around Fire Doors
Gaps around fire doors, especially around the top and sides, can indicate alignment issues, frame movement, or problems with the door leaf or ironmongery. Common causes may include loose hinges, damaged hinge screws, a warped door leaf, a twisted frame, incorrect door size, an unsuitable frame, missing door stops, old repairs, the door not sitting square, or poor latch alignment.
If a fire door does not close fully, fails to latch, drags on the floor, or leaves uneven gaps, it should be assessed by a competent person to confirm whether repair, adjustment, or replacement is required.
Can Fire Door Gaps Be Repaired?
Some fire door gaps can be repaired. Others mean the door or frame may need replacement.
Repair may be possible where:
- hinges need adjustment or replacement
- seals are missing or damaged
- the closer needs adjustment
- the frame needs minor repair
- the door is slightly misaligned
- suitable compatible products can be used
Replacement may be needed where:
- the door has been heavily cut
- the door leaf is damaged
- the frame is unsuitable
- the door is warped
- certification evidence is missing and compliance cannot be shown
- gaps are excessive and cannot be corrected safely
- the door has been modified incorrectly
- the door assembly no longer performs as required
Fire door repairs should be based on the door’s certification, manufacturer guidance and competent assessment.
Fire Door Gap Fillers and Seals
Fire door gap fillers, intumescent strips, smoke seals, threshold seals and drop-down seals may be part of a compliant solution, but they should not be used casually.
The wrong product can create new problems, such as:
- stopping the door from closing properly
- damaging the door’s certification
- interfering with smoke control
- causing latch failure
- hiding a serious frame or alignment issue
- giving a false sense of compliance
A fire door is a complete assembly. The door leaf, frame, seals, hinges, closer, glazing and ironmongery all need to be compatible.
How to Check Fire Door Gaps Safely
A responsible person, managing agent or property manager can carry out simple visual checks to identify obvious issues.
A basic visual check may look for:
- visible excessive gaps
- uneven gaps
- missing or damaged seals
- door not closing fully
- door not latching
- damaged frame
- damaged door leaf
- broken closer
- fire door wedged open
- signs of poor repair
- smoke seals missing where expected
- daylight visible around the frame
- gaps between double doors
GOV.UK guidance says Regulation 10 checks are intended to be simple and basic visual checks and do not involve technical examination of fire resistance. Where damage or issues are found, more detailed checks or specialist involvement may be appropriate.
Fire Door Gap Regulations UK
Fire door gap requirements are part of wider fire door compliance. They may be considered under:
- Building Regulations guidance
- fire risk assessment findings
- Fire Safety Order duties
- Fire Safety (England) Regulations 2022 where applicable
- manufacturer instructions
- fire door certification evidence
- inspection and maintenance records
Approved Document B provides fire safety guidance for residential homes, flats, residential accommodation, schools, colleges and offices.
For multi-occupied residential buildings above 11 metres, the Fire Safety (England) Regulations 2022 require responsible persons to carry out quarterly checks of communal fire doors and best-endeavour annual checks of flat entrance doors.
Common Fire Door Gap Defects
Common defects include:
- excessive top gaps
- excessive side gaps
- large bottom gaps
- uneven gaps
- gaps between double fire doors
- missing intumescent strips
- damaged smoke seals
- damaged door frames
- loose hinges
- damaged closers
- door not latching
- door not closing fully
- door leaf over-trimmed
- incompatible threshold products
- poor previous repairs
These issues should be recorded and reviewed as part of fire door maintenance.
Frequently Asked Questions
How do you fix fire door gaps?
Fire door gaps should be fixed by identifying the cause first. The solution may involve adjustment, hinge repair, seal replacement, frame repair, threshold work or door replacement. Fire door repairs should be handled by a competent person.
What is the maximum gap around a fire door?
There is no single answer that applies to every fire door. The acceptable gap depends on the fire door assembly, manufacturer guidance, certification evidence, seals and location. Excessive or uneven gaps should be assessed.
What is the maximum gap under a fire door?
The acceptable bottom gap depends on the door type, threshold detail, smoke control requirement and manufacturer guidance. A large bottom gap should be inspected because it may affect smoke and fire protection.
Can I use filler to fix fire door gaps?
Do not use ordinary filler, foam or draught strips unless the product is suitable for the specific fire door assembly. Incorrect products can compromise the door’s performance.
Are fire door gaps a compliance issue?
Yes. Excessive gaps can be a compliance issue because they may affect the door’s ability to resist fire and smoke spread.
Why do fire door gaps get bigger?
Fire door gaps can increase because of hinge wear, frame movement, building settlement, humidity, impact damage, poor installation or door warping.
Can a fire door with large gaps be repaired?
Sometimes. Minor alignment or seal issues may be repairable, but heavily cut, damaged or unsuitable doors may need replacement.
Should fire door gaps be checked regularly?
Yes. Fire doors should be checked regularly, especially in blocks of flats, HMOs, workplaces, commercial buildings and managed properties.
Who should repair fire door gaps?
A competent person should repair fire door gaps. Fire doors are safety-critical and should not be treated like normal internal doors.
Do fire door gaps need to be recorded?
In managed buildings, it is good practice to record fire door defects, inspections and remedial works as part of fire safety management.