Apartment entrance door set
Take a fire door set apart.
Closing action
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Open the door and let go: it should close fully on its own and click into its latch, without being so strong that people struggle to open it.
Select a part, on the door or above, to see what it does and what to look for. Drag the door to turn it and see the outer face.
A drawing of how a door set looks. It does not show that any door is certified.
In plain English
Anatomy of a Fire Door
A fire door is more than just a heavy door. It is a complete system, called a doorset, and every part has a job to do. If one part is missing, damaged or wrong, the whole door can fail when it matters most. Here is what each part does, in plain English.
All dimensions are typical guidance only. The door manufacturer’s certification and test evidence always take precedence.
01 The Door Leaf
The door leaf is the part that opens and closes, and it is the main barrier against fire and smoke. Fire door leaves usually have a solid, dense core, unlike the hollow doors you find in many homes. Their edges are finished with strips of timber called lippings. These are mainly on the hinge and lock sides, and sometimes on the top and bottom too. As a guide, a 30-minute fire door (FD30) is typically about 44 mm thick and a 60-minute door (FD60) is typically about 54 mm thick. A genuine fire door should carry a label or plug from its manufacturer so its rating can be checked. Cracks, holes, warping or home-made alterations, such as cutting in a new letterbox, can all stop it working.
02 The Door Frame
The frame is the fixed surround that the door hangs in, and it must be just as strong as the door. As a rule of thumb, a frame is around 30 mm or more thick. It must also be deep enough for the door leaf plus a rebate or ‘stop’, so the door closes neatly and flush. Frames for 30-minute doors are typically softwood, and frames for 60-minute doors are typically hardwood. MDF can be used for either where the manufacturer’s test evidence supports it. The frame and leaf must be compatible with each other. A damaged, rotten or twisted frame can leave gaps that let fire through.
03 The Gaps Around the Door
The small gaps between the door and its frame matter a great deal. On a typical timber fire door, the gaps at the top and sides should be between 2 mm and 4 mm, and the gap at the bottom should be no more than 8 mm. If the gaps are too big, fire, heat and smoke can get through. If they are too tight, the door may not close properly. Either way, it is a fault.
04 Intumescent Seals
Intumescent seals are thin strips set into the edge of the door or frame, running all the way around the doorset. In normal use you would hardly notice them. When they are heated past a certain temperature in a fire, they swell up and close the gaps around the door, which stops heat, flames and hot gases getting through. Modern 30-minute fire doors typically have at least one 15 mm strip. 60-minute doors typically have two strips, or a single wider strip of more than 15 mm. Older fire doors may have smaller seals, or seals hidden from view. The right seal is always whatever the door’s manufacturer tested it with.
05 Smoke Seals
Intumescent seals only react to heat, but smoke can travel long before things get hot, and cold smoke is a major cause of death in fires. Smoke seals deal with this. They are often built into the intumescent strip as a small brush or flexible blade (fin) that touches the door or frame when it is closed. They can also be separate rubber or compressible seals, either fitted into a groove or stuck onto the surface of the frame or door edge. You see these especially between the two leaves of double doors. Smoke seals must never be painted over, because even one coat can stop them working. Doors rated for smoke control carry an ‘s’ in their rating, for example FD30s.
06 The Threshold (Bottom) Seal
The gap under the door, between the door and the floor or floor covering, needs sealing against smoke too. Some door frames have a built-in threshold across the bottom, making a four-sided frame. More commonly, a drop-down seal is fitted. This is an automatic seal hidden in the bottom of the door, and when the door closes fully, it pushes a rubber gasket down onto the floor to make a tight seal. When the door opens again, it lifts back up.
07 Hinges
The hinges carry the whole weight of a heavy fire door, so they have to be up to the job. Modern fire doors need at least three steel hinges per door leaf, and these should be fire rated and carry a CE or UKCA mark. All the hinges on a door should match. Older doors may instead have substantial, solid hinges that were suitable when the door was first fitted. Hinges should be clean, with no excess oil or debris. They should also be securely fixed, with a screw in every fixing hole and none missing. Spring hinges and rising butt hinges are not normally suitable for fire doors.
08 The Door Closer
The closer is arguably the most important piece of hardware on a fire door, because a fire door only works when it is shut. The most common type is an overhead unit fixed to the door with an arm attached to the frame. Every fire door, apart from those that are kept locked, needs a working self-closing device. When you open the door and let go, it should close fully on its own and click into its latch. It also must not be so strong that people struggle to open it. A leaking, damaged or disconnected closer means the door will not protect you.
09 Locks, Latches and Handles
The latch holds the door firmly shut so fire pressure cannot push it open. Locks and latches on fire doors should be approved for fire door use, and fitted neatly into the door and frame with no oversized cut-outs. Handles should spring back to level on their own. On escape routes, you must be able to open the door from the inside in a single action, such as with a thumb-turn or push bar, without hunting for a key.
10 Glazing (Glass Panels)
If a fire door has glass in it, that glass must be special fire-resisting glass, rated to match the door. Ordinary glass will shatter quickly in a fire. Old-style Georgian wired glass is not accepted as fire-rated without test evidence. The glass is held in with beads and special seals that must be tight and undamaged. Glass panels cannot be added to an existing fire door afterwards. A door that needs a vision panel has to be replaced with one made that way in the factory.
11 Letterboxes, Spy-Holes and Air Grilles
Anything that goes through a fire door is a potential weak spot. Letterboxes and door viewers must be fire-rated products with fire seals built in. On smoke-rated doors, the letterbox needs a smoke seal as well. Air transfer grilles, the vents some doors have, must contain an insert that swells shut in a fire. On smoke-rated doors, the grille must be the type that closes automatically. These openings must be made by the manufacturer, never cut on site.
12 Fanlights, Side Panels and Overpanels
Some doorsets include extra glass or solid panels above (fanlights or overpanels) or beside (sidelights) the door. These count as part of the fire door and must give the same fire protection as the door itself.
13 Fire Stopping Around the Frame
Even a perfect fire door is useless if fire can simply go around it. The gap between the door frame and the wall must be properly sealed with tested fire-stopping materials, such as fire-rated foam, intumescent mastic or the correct packers. Ordinary building foam, loose mineral wool or plastic packers do not count. This junction is usually hidden behind the decorative trim (architrave), which is why a full check may need that trim removing.
14 Fire Door Signage
Most fire doors in communal and commercial areas must display a blue and white sign, usually ‘Fire Door Keep Shut’ or ‘Fire Door Keep Locked’. The sign goes on both sides at around eye level. Cupboards and risers usually only need a sign on the outside. A sign reminds people that the door is a life-safety device, not just a door, and that it must never be wedged open. Front doors to individual flats don’t need these signs.
15 Hold-Open Devices
Sometimes a fire door needs to stay open for everyday use. The only safe way to do this is with an approved hold-open device that is linked to the fire alarm and releases the door automatically when the alarm sounds. Wedges, hooks and ordinary magnetic door stops are not allowed.
Every fire door should be inspected regularly by a competent, third-party certified inspector. If you are unsure whether your fire doors would protect you, get in touch with Jewel Passive Fire Protection.