If you manage a London property, you will encounter fire doors in corridors, stairwells, plant rooms and other locations. Understanding what a fire door is — and what it is designed to do — can help you plan inspections, interpret reports and communicate more clearly with contractors, residents and duty holders.
A fire door is not simply a heavier or thicker door. It is part of a tested door set that may include the leaf, frame, seals, ironmongery and closing device, all intended to work together in a fire situation. This guide explains the basics in plain language, without legal advice or guarantees about compliance.
Where visible issues are found, structured inspection records can support remedial planning and clearer documentation. Responsible persons and duty holders should confirm applicable duties and seek competent advice where required.
Simple definition of a fire door
A fire door is a door assembly designed to resist the passage of fire and smoke for a specified period, helping to compartmentalise a building and protect escape routes. In practice, the term usually refers to a complete fire door set — the door leaf, frame, seals, hardware and closing arrangement — rather than the leaf alone.
Fire doors are manufactured and tested as part of a system. The performance of the set depends on all components working together as intended. A standard internal door, even if solid or heavy, is not automatically a fire door unless it forms part of a suitable, correctly installed and maintained fire door set.
Fire resistance is typically expressed in minutes — for example, FD30 or FD60 — indicating the period for which the door set is designed to resist fire when tested under controlled conditions. The rating on a label or certificate relates to the tested assembly, not to individual parts in isolation.
What fire doors are used for
Fire doors serve several related purposes in managed buildings. They can help limit the spread of fire and smoke between compartments, protect escape routes so occupants have time to leave safely, and reduce the risk of fire reaching areas where it could cause greater harm.
In blocks of flats, offices, schools, care homes and other settings, fire doors may be found on corridors, stairwells, plant rooms, risers and between different fire compartments. Their location and specification depend on the building design, use and applicable requirements — which responsible persons should confirm with competent advice where required.
Fire doors also support broader fire safety arrangements. They work alongside alarms, emergency lighting, signage and evacuation plans. A fire door that does not close properly, has damaged seals or has been altered without suitable controls may not perform as intended, which is why visible checks and professional inspections can be valuable where recorded.
How fire doors work in a building
In a fire situation, a fire door is designed to remain closed and resist the passage of flames and hot gases for its rated period. Intumescent seals fitted around the door edges may expand when exposed to heat, helping to fill gaps between the door leaf and frame. Smoke seals may also be present to restrict smoke passage at ambient temperatures.
The door must close fully into its frame without obstruction. Self-closing devices — typically overhead closers or spring hinges — are commonly fitted so the door returns to the closed position after use. If a door is wedged open, propped with furniture or fitted with incompatible hold-open devices, its ability to perform in a fire may be compromised.
Fire doors form part of a building's passive fire protection strategy. They do not extinguish fire; they contain it and buy time. Their effectiveness depends on correct specification, installation, maintenance and use. Regular visible checks and structured inspections can help identify issues before they affect performance, depending on scope and access.
Key parts of a fire door set
Understanding the main components can help property teams interpret inspection findings and brief contractors more clearly. The following parts are commonly reviewed during visible fire door checks, though the exact configuration varies by door type and manufacturer.
- Door leaf — the moving panel, usually solid or with approved fire-rated glazing
- Frame and architrave — the fixed surround that the leaf closes against
- Intumescent seals — strips that expand under heat to seal gaps at the door edges
- Smoke seals — brush or fin seals that restrict smoke passage at ambient temperatures
- Hinges — typically three or more fire-rated hinges with suitable fixings
- Self-closing device — overhead closer or spring hinges to ensure the door closes
- Latch or lock — suitable fire-rated ironmongery that allows the door to latch fully
- Glazing — fire-rated glass and beads where vision panels are present
- Signage — fire door keep shut or keep locked signs where applicable
- Threshold — may include a drop seal or smoke seal at the bottom edge
Why fire doors need to close properly
A fire door that does not close fully into its frame cannot compartmentalise effectively. Gaps that are too wide, misaligned hinges, damaged closers or obstructions on the floor can all prevent proper closure. Even minor issues can affect how the door performs under fire conditions.
Self-closing is a fundamental requirement for most fire doors in common areas. Without a working closer, doors may be left open during normal use, which defeats their purpose. Hold-open devices, where used, must be compatible with the fire strategy and connected to the fire alarm system where applicable — not improvised with wedges or door stops.
Gap tolerances are specified as part of the tested door set. Gaps that exceed acceptable limits may allow smoke and fire to pass more quickly. During inspections, gap measurements and closure checks may be recorded where included in scope, helping property teams prioritise remedial works.
Common signs a fire door may need attention
You do not need to be a fire door specialist to notice visible issues that may warrant further review. The following signs are commonly recorded during inspections and may indicate that a door set needs attention, repair or replacement — depending on the finding and competent advice.
- Door wedged or propped open during normal use
- Closer missing, damaged or not closing the door fully
- Gaps around the door that appear excessive or uneven
- Intumescent or smoke seals missing, damaged or painted over
- Hinges loose, damaged or with incorrect fixings
- Door leaf damaged, warped or with unauthorised holes or vision panels
- Glazing cracked or fitted with non-fire-rated glass
- Signage missing, damaged or incorrect
- Frame damaged, distorted or with visible gaps at the wall interface
- Latch not engaging or door not sitting flush in the frame
Why inspection reports are useful
Visible checks by property staff can help spot obvious issues between formal inspections. However, a structured fire door inspection report can provide a more systematic record of door condition across a building or portfolio, depending on scope and access.
Reports may include door references, photographs of visible defects, observations on seals, closers, gaps and signage, and notes to support remedial planning. They do not prove compliance or replace competent advice, but they can help managing agents, landlords and duty holders maintain clearer documentation and track remedial actions over time.
For office buildings, blocks of flats and other managed properties in London, regular inspection records can support internal audit processes and communication with contractors. If you are planning inspections across multiple doors or sites, a survey or portfolio inspection may help establish baseline records before prioritising remedial works.