A fire door looks, in most respects, like an ordinary door. Open it, close it, walk through it hundreds of times. It sits quietly in a corridor or stairwell, and nothing happens — which is exactly the point. The problem is that this unremarkable appearance makes it easy to overlook. And a fire door that is not properly installed, maintained, and kept operational is not a fire door at all.

In our experience carrying out fire door inspections across London, we see the same mistakes repeatedly — in residential blocks, commercial buildings, healthcare facilities, and education premises alike. Some are the result of poor original installation. Many more are the result of neglect, or of well-meaning but ill-informed decisions made by building occupants or maintenance teams.

Here are the five we see most often, and what you can do about each one.

1

Incorrect or Missing Seals

Intumescent strips and cold smoke seals are among the most important — and most frequently defective — components of a fire door assembly. Intumescent strips expand rapidly when exposed to heat, sealing the gap between the door and the frame and preventing fire from passing through. Cold smoke seals prevent the movement of smoke around the door when the strip has not yet activated — critically important, since smoke inhalation causes the majority of fire-related deaths.

We regularly find doors where the intumescent strip is missing entirely — often because a door has been replaced without the correct hardware — or where the seal has deteriorated and is no longer providing a continuous barrier around the door's perimeter. In some cases, seals have been painted over during decoration works, which can significantly impair their performance.

The fix: Inspect all seals at least annually (and every quarter in buildings over 18 metres). Replace any seal that is damaged, missing, or has lost its integrity. Never paint over intumescent strips.

2

Incorrect Gap Tolerances

A correctly hung fire door should have a gap of no more than 3mm between the door leaf and the frame on the top and sides, and a gap of between 8mm and 10mm at the bottom (to clear the floor finish). These tolerances are not arbitrary — they are the gap within which the intumescent strip is designed to expand and form an effective seal.

When gaps are too wide, the strip cannot bridge them effectively. We find oversized gaps frequently on older doors where the frame has moved over time, or where a door has been rehung without the required checks. We also find doors that have been installed with too small a gap at the bottom — often because the building has had new flooring fitted — meaning the door rubs on the floor or fails to close properly.

The fix: Use a 3mm gauge card to check top and side gaps during every inspection. Adjust hinges or rehang the door if gaps are out of tolerance. If a floor finish change has affected the bottom clearance, assess whether adjustment or a new door is required.

3

Doors Being Propped Open

This is perhaps the most universal fire door problem — and also the most frustrating, because it is entirely behavioural. In residential blocks, residents prop open communal fire doors for convenience: to carry shopping, to let the dog through, to improve air flow. In commercial settings, staff wedge fire doors open to ease movement between areas. In healthcare settings, fire doors are sometimes propped open to allow patients to be moved more easily.

A fire door that is propped open provides zero fire resistance. In the event of a fire, it will not contain the spread of smoke and flame. In certain buildings, this can be addressed by fitting hold-open devices linked to the fire alarm system — which release the door automatically when the alarm activates — but these must be correctly installed and maintained.

The fix: Remove any unauthorised door stops or wedges during inspections. Consider whether hold-open devices linked to the fire alarm are appropriate. In residential buildings, include clear fire door messaging in resident communications.

4

Defective or Missing Door Closers

A fire door that does not close — fully, reliably, and every time — is not a fire door. Yet defective door closers are among the most common deficiencies we find. Closers wear out over time, particularly on high-traffic doors. They can be set to close too slowly, meaning the door does not latch. They can lose hydraulic pressure, causing the door to stop short of the frame. They can be damaged by impact. And in some cases, they have simply been removed because a resident or occupant found them inconvenient.

The closer must be set to bring the door fully home against the frame and latch under its own power, from any open position. A door that closes from 90 degrees but stops at 10 degrees is non-compliant. A door that closes but does not latch is non-compliant.

The fix: Test every door closer as part of each inspection. Open the door to 90 degrees and release it — it must close and latch fully. Replace any closer that fails this test without adjustment. Never remove a fire door closer.

5

Using the Wrong Door — or No Certification at All

Not all fire doors are equal. A door rated FD30 is certified to resist fire for 30 minutes; an FD60 door for 60 minutes. Building regulations and fire risk assessments specify which rating is required in each location — and using the wrong rating, or a door that has no certification at all, is a significant compliance failure.

This is a particular problem in older buildings where original fire doors have been replaced over time by maintenance teams without the correct certification checks. A non-certified replacement door might look identical to the original, but it may provide no meaningful fire resistance. Every fire door should carry a plug or label certifying its rating and manufacturer. When we inspect doors that have no legible certification, we treat them as non-compliant until evidence of their rating can be provided.

The fix: Check for certification labels or plugs on every door during inspection. Cross-reference the door's rating against the building's fire risk assessment to confirm the correct rating is in place. Replace any uncertified door or door with the wrong rating.

A note on documentation: Under the Fire Safety (England) Regulations 2022, responsible persons in residential buildings must carry out regular fire door inspections and keep a record of the findings. A verbal check is not sufficient — every inspection should produce a written report, and any defects identified should be tracked through to remediation.

What to Do If You Find a Defective Fire Door

A non-compliant fire door must be treated as an active fire risk until it is repaired or replaced. Where the defect is minor — a damaged seal, a closer that needs adjustment — it should be remediated as quickly as possible. Where the defect is more significant — a door that will not close, a door with no certification, a door with excessive gaps — the remediation should be treated as urgent.

In the meantime, if a fire door is found to be seriously defective, consider whether it needs to be taken out of service and temporarily secured, and whether the building's fire risk assessment needs to be reviewed in light of the deficiency.

How Ultra-Fire Can Help

Ultra-Fire carries out fire door inspections, maintenance, and replacement across London. Our team has the expertise to identify all of the deficiencies described in this post — and to remediate them to a fully compliant standard. We provide clear written inspection reports after every visit, giving you the documentation you need to demonstrate compliance with your legal obligations.

Whether you manage a single building or a large portfolio, we can work with you to establish an ongoing inspection and maintenance programme that keeps your fire doors in compliant condition all year round.

‍