The 8 Most Common Fire Door Defects and How to Spot Them

When FDIS data from over 100,000 inspections shows that 75% of fire doors fail to meet the required standard, the natural question is: what are they actually failing on? It's not 75% of fire doors catastrophically compromised. It's 75% with at least one defect — and a handful of defect types account for the vast majority of failures.

If you're a managing agent conducting quarterly inspections under regulation 10, knowing what you're most likely to find — and what each defect means for fire safety — helps you inspect faster and prioritise remediation more effectively.

Here are the eight defects that appear most frequently across residential fire door inspections, ranked by how often they're found.

1. Excessive or Inconsistent Gaps

What it is: The gap between the door edge and the frame exceeds 3-4mm, or is noticeably wider in some places than others.

Why it's so common: Fire doors drop on their hinges over time. Heavy traffic, loose hinges, and building movement all contribute. A door installed with perfect 3mm gaps can develop 6-8mm gaps at the top within a few years. Gaps also widen at the bottom if the closer is too strong and the door swings hard into the frame repeatedly.

How to spot it: Close the door and look at the gap on all four sides. Use a £1 coin (roughly 3mm thick) as a gauge. If the coin passes through easily with space to spare, the gap is too wide. If the gap is tight at the bottom and wide at the top, the door has dropped.

Why it matters: Gaps are the primary route for fire and smoke to pass around a closed fire door. A 6mm gap roughly doubles the area through which smoke can travel compared to a 3mm gap. Intumescent seals are designed to expand and fill a specific gap width — if the gap is too wide, the expanded seal may not fully bridge it.

What to do: If the gap is caused by dropped hinges, re-hanging the door or replacing the hinges often resolves it. If the door leaf has warped, planing may correct it (only if the door construction allows it — solid core doors can be planed slightly, but cutting into the core compromises the fire rating). If gaps are beyond correction, the door needs replacing.

Priority: Critical if gaps exceed 4mm, especially at the top and closing edge.

2. Damaged or Missing Intumescent Seals

What it is: The intumescent strip — a thin strip embedded in the door edge or frame rebate that expands in heat to seal gaps during a fire — is missing from one or more edges, cracked, or painted over.

Why it's so common: Intumescent strips degrade over time. UV exposure, cleaning chemicals, and physical wear all contribute. In many older buildings, intumescent strips were never fitted — the doors predate the current standards, or were installed when seal requirements were less stringent. Painting is a particular problem: decorators coat the strips in emulsion during corridor redecoration, which prevents the strip from expanding.

How to spot it: Run your finger along the door edges where they meet the frame. The intumescent strip should be continuous along both vertical edges and the top edge. Check for: strips that are missing entirely, strips that are cracked or crumbling, strips where paint has been applied over the surface. The strip is usually a slightly different colour or texture from the door edge.

Why it matters: In a fire, the intumescent strip swells to roughly 5-10 times its original width, sealing the gap between door and frame. Without it, or with it blocked by paint, the fire can pass around the door edge. FDIS identifies seal defects as one of the top three reasons for fire door failure.

What to do: Missing or damaged strips need replacing. This is a relatively straightforward remedial — new intumescent strips can be routed into the door edge or applied as surface-mounted strips. The important thing is matching the specification: the replacement strip must match the original fire door certification (thickness, expansion rate, material type). Painted-over strips need the paint removed and the strip checked for damage underneath — if the strip is sound under the paint, removal may be sufficient.

Priority: Critical if missing from any edge. Important if partially damaged.

3. Self-Closing Device Failures

What it is: The door doesn't close fully into the frame on its own, or the self-closing device is missing entirely.

Why it's so common: Self-closers are mechanical devices under constant stress. Overhead closers can leak hydraulic fluid, lose tension, or develop bent arms. Concealed closers wear out. Rising butt hinges lose their lift. Beyond mechanical failure, self-closers are the component most frequently interfered with — residents disable them, adjust them, or wedge doors open because the closer makes the door inconvenient to use.

How to spot it: Open the door to roughly 90 degrees and let go. The door should close fully into the frame on its own, with the latch engaging. Not almost-closed — fully closed. If the door stops 10mm from the frame, that's a failure. Check for: a visible closer device (overhead arm, concealed closer, or rising butt hinges), signs of hydraulic fluid leaking from an overhead closer, a bent or disconnected closer arm, wedges or doorstops preventing closure.

Why it matters: A fire door that doesn't close in a fire provides zero protection. The entire point of a fire door is that it closes automatically and stays closed, containing fire and smoke to the compartment of origin. A door held open by a wedge, or a door with a faulty closer that stops 10mm short of the frame, is not doing its job.

What to do: If the closer exists but isn't working, adjust or replace it. If the closer has been removed, fit a new one. For overhead closers, check whether the arm and body are intact — if the body is leaking, it needs replacing rather than adjusting. Remove any wedges or doorstops and inform the building occupants why fire doors must not be held open. Note: some doors have legitimate hold-open devices connected to the fire alarm system — these release automatically when the alarm activates and are acceptable.

Priority: Critical. A non-closing fire door is functionally equivalent to no fire door.

4. Missing or Degraded Cold Smoke Seals

What it is: The cold smoke seal — a brush or rubber strip, typically fitted alongside the intumescent strip — is missing, flattened, or hardened.

Why it's so common: Cold smoke seals are softer than intumescent strips and wear out faster. Brush-type seals flatten over time, losing their ability to seal the gap. Rubber seals harden and crack. In heavy-traffic corridors, the constant opening and closing of the door accelerates this wear.

How to spot it: Check alongside the intumescent strip for a brush or rubber strip. It should be flexible and make contact with the frame when the door is closed. If the brush is flat and no longer springs back, or the rubber is rigid and cracked, it's not providing a seal.

Why it matters: Cold smoke seals prevent smoke from passing around the door before the intumescent activates. In the early stages of a fire — when smoke is the primary killer — these seals are the first line of defence. Intumescent strips only activate at high temperatures (typically above 140-200°C). Before that threshold, it's the cold smoke seal preventing smoke from entering the escape route.

What to do: Replace the seal. Cold smoke seals are inexpensive and straightforward to fit — they typically push into a groove in the door edge or are surface-mounted. Match the type (brush or rubber) and profile to the existing installation.

Priority: Important. Less immediately critical than intumescent failure, but a significant safety gap.

5. Missing Fire Rating Label

What it is: The fire rating label (typically a colour-coded plug or adhesive label showing FD30 or FD60) is not visible on the top edge or hinge side of the door.

Why it's so common: Labels fall off, are painted over during decoration, or were never applied (some older doors predate the labelling standard). In refurbished buildings, original doors may have been replaced with unlabelled substitutes. The label is a small detail that's easy to overlook during installation.

How to spot it: Check the top edge of the door (close the door and look down from above, or use a torch) and the hinge side edge. The label is usually a colour-coded plug (blue for FD30, red for FD60) or a printed adhesive label. Some doors have the rating stamped or engraved into the edge.

Why it matters: Without a label, you can't confirm the door's fire rating from visual inspection alone. This doesn't necessarily mean the door isn't fire-rated — it means you can't verify it is. For regulatory purposes, an unlabelled door is a door whose fire performance is unconfirmed.

What to do: Record the door as "fire rating label missing — rating unconfirmed." Check whether the door manufacturer or installation records can confirm the door's specification. If the door's fire rating cannot be confirmed from any source, it may need to be assessed by a fire door specialist or replaced with a certified door. Note: you cannot simply attach a new label to an existing door — the label must come from the manufacturer or installer as part of the door's third-party certification.

Priority: Important for record purposes. If other defects suggest the door may genuinely not be fire-rated (wrong thickness, hollow sound when knocked, visible non-fire-rated construction), escalate to critical.

6. Hinge Problems

What it is: Fewer than three hinges, missing screws, loose fixings, or visible sagging.

Why it's so common: Hinge screws work loose over time, especially in heavy-traffic doors. Door-mounted items (closers, signage holders) add weight that accelerates hinge wear. In some buildings, doors were originally installed with only two hinges — below the minimum of three required for fire doors.

How to spot it: Count the hinges — there should be at least three. Check for empty screw holes (look at each hinge plate carefully). Grip the door at the lock side and push gently up and down — any movement indicates loose hinges. Look at the gap pattern: if the top gap is wider than the bottom, the hinges are allowing the door to drop.

Why it matters: Hinges keep the door properly aligned in the frame. When hinges fail, the door drops, gaps widen, seals lose contact, and the closer has to work harder to pull the door into the frame. A single loose hinge can cascade into multiple other defects.

What to do: Tighten loose screws. If screws won't hold (the fixing hole is stripped), use longer screws or fit wall plugs. Replace damaged or missing hinges — use CE-marked fire door hinges that match the door's fire rating. If the door only has two hinges, a third hinge needs fitting (by someone competent to do so — the hinge position and screw pattern must maintain the door's fire performance).

Priority: Important. Hinge problems are progressive — they get worse over time, and fixing them early prevents cascade failures.

7. Missing or Illegible Signage

What it is: The "Fire Door — Keep Shut" sign (or "Fire Door — Keep Locked" for locked fire doors) is missing, illegible, or detached.

Why it's so common: Signs are stuck on with adhesive and eventually fall off. They fade in sunlight. They get painted over. In some buildings, signs were never fitted. It's a low-priority item that gets missed during general maintenance.

How to spot it: Look at the face of the door for the sign. It should be present, legible (readable from a reasonable distance), and securely attached.

Why it matters: The signage tells building occupants that the door is a fire door and must be kept closed. Without it, there's no visual instruction to prevent the door being wedged open. The sign is a simple, cheap safety measure — its absence is often the easiest defect to fix.

What to do: Fit a new sign. Fire door signage is standardised and inexpensive. Use self-adhesive signs rated for the surface type (painted wood, laminate, etc.). Ensure the wording matches the door's function: "Keep Shut" for most fire doors, "Keep Locked" for fire doors that should remain locked, "Automatic Fire Door — Keep Clear" for hold-open devices.

Priority: Monitor — lowest priority among the eight defects listed here, but easy and cheap to fix. There's no reason to leave it unresolved.

8. Unauthorised Modifications

What it is: Changes to the door that were not part of the original fire-rated installation — cat flaps, letterboxes (non-fire-rated), additional lock holes, spy holes, ventilation grilles, or holes from removed fittings.

Why it's so common: Most common on flat entrance doors. Leaseholders modify their front doors without understanding that any penetration of the door leaf can compromise the fire rating. A letterbox cut into an FD30 door without a fire-rated letterbox plate creates an opening that fire and smoke can pass through. A cat flap is a hole in a fire door.

How to spot it: Look at the door face and edges for any fittings or holes that weren't part of the original installation. Common signs: a letterbox without visible intumescent protection, a cat flap (any cat flap in a fire door is a defect), filled holes from removed fittings, additional lock cylinders that required boring through the leaf.

Why it matters: Every penetration of the door leaf creates a potential fire path. Fire doors are tested and certified as complete assemblies — the leaf, the frame, the seals, the ironmongery. Modifying any component outside the certified specification invalidates the fire rating.

What to do: For letterboxes: fit a fire-rated letterbox with intumescent liner (these are designed to seal in a fire). For cat flaps: the cat flap must be removed and the hole repaired or the door replaced — there is no fire-rated cat flap. For additional lock holes: assess whether the penetration is significant enough to compromise the fire rating (a fire door specialist can advise). For filled holes: check that the filler provides fire resistance equivalent to the door leaf (standard wood filler does not).

Priority: Critical for any modification that creates an open pathway through the door leaf. Important for modifications that may compromise the fire rating.

Using This List on Your Inspections

These eight defects cover the vast majority of what you'll find during quarterly and annual fire door inspections. A systematic approach:

1. Start each door with the gap check (defect #1) — it's visual and immediate
2. Run your hand along the edges for seals (defects #2 and #4)
3. Test the closer (defect #3) — open and release
4. Check hinges (defect #6) — count and test for movement
5. Look for the label (defect #5) and signage (defect #7)
6. Check for modifications (defect #8) — especially on flat entrance doors

Generate a checklist based on these checks for your building →

For a detailed walkthrough of the full inspection process, see our step-by-step guide to checking fire doors.

For guidance on managing the remediation process once you've found defects, see our guide to fire door remedials.

The Pattern Behind the Numbers

The 75% failure rate sounds alarming, but understanding the pattern makes it manageable. Most failures come from progressive wear (seals degrading, hinges loosening, gaps widening) rather than catastrophic defects. This means:

• Quarterly inspections catch problems early — before a slightly loose hinge becomes a dropped door with 8mm gaps and broken seals
• Remediation costs are lower when you catch defects early — tightening screws is cheaper than replacing a door
• The failure rate drops after the first remediation cycle — the initial inspection on an unmaintained building will find the accumulated backlog. After that, each quarter catches only the new wear since the last inspection

The challenge for managing agents isn't the individual defect — it's tracking hundreds of defects across dozens of buildings through remediation to completion, while the next quarterly inspection round is already approaching.

FireDoorReady is being built to help managing agents record defects per door, prioritise by severity, track each one through remediation, and evidence completion — across every building in the portfolio. Join the waitlist →

This guidance applies to England. Scotland, Wales, and Northern Ireland have separate fire safety legislation.

This article is general guidance, not legal advice. Consult a fire safety professional or legal adviser for advice specific to your buildings.

Sources

• FDIS survey: three-quarters of UK fire doors fail inspection — Guild of Architectural Ironmongers
• Fire Safety (England) Regulations 2022, regulation 10 — legislation.gov.uk
• Fire Safety (England) Regulations 2022: fire door guidance — GOV.UK