What a fire door is (and what it isn't)
A fire door is built to do one job: stop a fire spreading from one room to the next for long enough to let everyone get out. It holds back flames, heat and smoke. It also keeps the stairs or hallway clear as an escape route.
To be sold as a fire door, the design has to pass a furnace test, where a full doorset is fitted into a wall and one side is heated to fire temperatures. If it holds for 30 minutes, it's an FD30. The test covers the whole assembly, not just the door, which is why the fitting matters so much.
A fire exit door is a way out of a building, usually with a push bar. It may or may not be fire rated. A fire door is about holding fire back inside the building.
The parts that make it work
The core
A fire door has a solid, dense core that chars slowly instead of burning through. A normal hollow-core door can burn through in minutes.
Intumescent seals
Thin strips set into the edge of the door or the frame. When they get hot they swell up and fill the gap between door and frame, sealing out fire. Some come with a brush or rubber fin as well to stop cold smoke, which is often more dangerous than the flames.
The frame
The door is only as strong as what holds it. A fire door should hang in a fire-rated frame or lining that matches its rating.
Hinges, latch and closer
Fire-rated hinges and a latch that holds the door shut under pressure. Where the rules ask for it, a self-closer pulls the door shut on its own. You'll find more on the hardware in our door hardware guide.
Glass
Glazed fire doors use special fire-rated glass, set in fire-rated beads. Ordinary glass would crack and fall out.
How to spot a fire door
Not sure if the doors in your home or a flat you're buying are fire doors? Look for these, in this order:
- A label or plug on the edgeOpen the door and look along the top edge and the hinge edge. Certified fire doors carry a label or a small coloured plug from a certification scheme. This is the best evidence there is.
- The thicknessMeasure the edge. A fire door is usually 44mm thick (54mm for FD60). A 35mm door is almost certainly not one.
- Seals round the edgeLook for a strip about 10 to 20mm wide set into the door edge or the frame.
- Three hingesMost fire doors have three hinges, often stamped with a CE or UKCA mark.
- A closerFlat front doors and garage doors into the house should close on their own.
If the door ticks every box but has no label, it may still be a fire door, but nobody can prove it. For building control or a landlord's records, a door without evidence is usually treated as not being one.
FD30, FD60 and what the S means
FD stands for fire door. The number is how many minutes it held back fire in the test. FD30 doors are the standard for homes, from loft conversions to flat front doors. FD60 doors are used where more protection is needed, mostly in commercial and larger buildings. An S on the end, as in FD30S, means the door also has smoke seals.
We've written a full breakdown of the ratings and where each one is used: FD30 and FD60 fire doors explained. To find out which doors in your home need to be fire doors at all, read our guide to fire door regulations for homes.
Common fire door myths
- "Any solid door is a fire door." No. A solid door without certification, seals and the right hardware hasn't been proven to hold back fire.
- "Fire doors look institutional." Not any more. We sell 57 FD30 doors in oak, white, grey and black, panelled and glazed, that look just like the standard doors next to them.
- "I can trim it as much as I need." Every fire door has a trimming limit. Go past it and the certificate no longer covers the door.
- "I can paint over the seals." Paint the door by all means, but keep paint off the intumescent strips so they can still swell.
- "Wedging it open is fine when we're home." A fire door only works when it's shut.
A two-minute check for your fire doors
Do this every six months and when you move in:
- Open the door fully and let go. If it has a closer, does it shut and latch on its own?
- Look at the gap round the top and sides. Is it even and about 3mm, roughly the thickness of a £1 coin?
- Are the seals all there, not painted over, torn or missing?
- Are the hinges tight, with no missing screws?
- Is any glass cracked or loose?
If anything fails, it's worth getting it fixed or replaced. Our fitters supply and hang certified fire doors as a complete set. See what fitting costs or book fire door fitting in Leeds.
