Fire Door Hinges: How Many, What Type, and the Rules

How many hinges does a fire door need?

A timber fire door is normally hung on a minimum of three metal hinges. That is the standard guidance figure in the BWF Fire Door Alliance Best Practice Guide, which states plainly that 'a minimum of 3 fire rated hinges must be used with correct intumescent pads, location and fixings'. It is not a legal maximum, and it is not a figure you should read as universal: the governing number is whatever the door's certificate and installation instructions specify for that exact leaf.

Three hinges — rather than the two you often see on an ordinary internal door — do two jobs. They carry the extra weight of a substantially built fire door leaf, and, just as importantly, they hold the leaf flat so it does not bow and pull away from the frame as it heats up in a fire. A leaf that bows opens a gap at the edge, and a gap is where fire and smoke get through. Heavier or taller leaves place more load on the hinges, so many manufacturers specify a fourth hinge (and occasionally more) for taller doors. Because that threshold is set by the individual test and manufacturer's instructions rather than by a single universal rule, the safe answer is always: fit the number the certificate tells you to, in the positions it tells you to.

What type and material of hinge does a fire door need?

The single most important rule about the type of hinge comes from Approved Document B, the statutory guidance supporting the Building Regulations in England. Appendix C, paragraph C10 states: 'Unless shown to be satisfactory when tested as part of a fire doorset assembly, the essential components of any hinge on which a fire door is hung should be made entirely from materials that have a minimum melting point of 800°C.' That is the wording in Volume 2 (Buildings other than dwellings); Volume 1 (Dwellings) sets the same 800°C requirement in its own fire-door appendix, Appendix B.

The logic is simple. A fire door only works if it stays hung on its frame while the fire burns. If the hinges soften or melt, the leaf drops, twists or falls out, and the barrier fails at exactly the moment it is needed. The '800°C' figure is a floor that keeps the load-bearing parts of the hinge intact for the rating period. Note the phrase 'essential components': it is the structural parts of the hinge — the knuckle, pin and leaves — that must clear the threshold. A minor non-structural part, such as a nylon washer, may be acceptable only where the specific doorset was fire-tested that way.

Which hinge materials pass, and which do not

In practice the melting-point rule points you towards steel, stainless steel, brass and phosphor bronze, which comfortably exceed 800°C. It rules out the materials people often reach for on ordinary doors: aluminium melts at roughly 660°C, and the zinc-based die-cast alloys sold as 'Zamak' or 'Mazak' melt far lower still — well below the 800°C line. Those materials are not automatically banned, but a hinge made from them can only go on a fire door if that exact hinge was proven satisfactory when the doorset was fire-tested. Absent that evidence, they do not comply.

What is BS EN 1935 and what grade should fire door hinges be?

BS EN 1935 is the European (and retained British) standard for single-axis hinges — the ordinary butt hinges a fire door swings on. The BWF Fire Door Alliance is explicit that conformity marking of fire door hinges 'must be tested to BS EN 1935' and used on fire or smoke doors and on escape routes. A compliant hinge is therefore CE or UKCA marked, tested to BS EN 1935 by an approved test house, and backed by a Declaration of Performance — the conformity marking regime that applies to construction products under the Construction Products Regulation.

BS EN 1935 classifies each hinge with an eight-part code. Each part records a different performance characteristic, so you can read a hinge's capabilities straight off its data sheet:

• Category of use — how demanding the traffic and duty are.
• Durability — the number of test cycles the hinge withstands (up to 200,000 for the most durable grades).
• Test door mass — the weight of door the hinge was tested to carry.
• Suitability for use on fire/smoke doors — the fire-critical part, graded 0 or 1.
• Safety — suitability for safety-in-use requirements.
• Corrosion resistance — performance in salt-spray testing.
• Security — whether the hinge contributes to burglary resistance.
• Grade — the overall hinge grade, from 1 (lightest duty) up to 14 (heaviest).

For fire doors, two of those parts matter most. First, the fire/smoke-door suitability grade: grade 0 means the hinge is not suitable for fire or smoke-resisting door assemblies, while grade 1 means it is suitable — but only where its contribution to the doorset's fire resistance has been satisfactorily assessed. A fire door hinge must be grade 1. Second, the overall grade: fire doors are heavy, so they are commonly specified with a heavy-duty grade. Grade 13 — a heavy-duty grade widely quoted as suitable for doors up to around 120 kg and tested to 200,000 cycles — is the grade most often seen on certificated fire door assemblies, though the certificate, not a generic grade, is the final word.

Do fire door hinges need intumescent pads?

Sometimes — and only where the door's test evidence says so. Cutting the recesses for hinges removes timber from the leaf and frame, and on some doorsets the fire test showed that those pockets needed protecting. Where that is the case, the certificate and installation instructions call for intumescent pads to be fitted behind the hinge blades. The BWF installation guidance instructs the fitter to 'ensure that intumescent pads are used under the hinge blades as specified in the installation instructions', and its post-installation checklist asks whether each hinge is 'fitted with correct intumescent pads if specified'.

The pads are a thin intumescent material that sits in the hinge recess. In a fire they expand to fill the void the ironmongery leaves in the leaf and frame, closing off a path that flame and hot gases could otherwise exploit. They work on the same principle as the intumescent strips and smoke seals around the door edge. The key point is that pads are certificate-driven: fitting them where the evidence does not require them, or leaving them out where it does, both count as departures from the tested specification. Follow the instructions for that specific doorset.

Why can't you swap fire door hinges freely?

Because a fire door is certificated as a complete, tested assembly — a doorset, with its leaf, frame, seals and ironmongery all part of the same fire test. The hinges are not an accessory bolted on afterwards; they are a component of the thing that passed the test. Change them for a hinge of a different type, size, material or grade, and you are no longer using the configuration the certificate covers. Unless the new hinge is compatible with the tested doorset, the fire performance is unproven and the certification can be invalidated.

The BWF Fire Door Alliance post-installation checklist captures what 'compatible' means in practice. Each hinge should be:

• Conformity marked for fire performance (CE or UKCA, to BS EN 1935) where applicable.
• Suitable for the fire door rating — the FD30, FD60 or higher rating of the leaf it hangs.
• Compatible with the door assembly or doorset — i.e. matching the tested specification.
• Fitted with the hinge manufacturer's supplied, fire-tested fixings, of the correct specification and length.
• Complete — every fixing hole filled, no missing screws.
• Fitted with the correct intumescent pads where the installation instructions specify them.
• Free from damage.

This is also why 'like-for-like' replacement is not as simple as it sounds. Swapping a worn or damaged hinge for the identical part specified by the door manufacturer, using their fixings, keeps you inside the certification. Reaching for a superficially similar hinge from a merchant's shelf does not — even a small difference in size, grade, plate thickness or material can take the door outside its test evidence. When you are choosing a replacement, work from the door's certificate and the manufacturer's schedule of tested hardware, not from what looks close enough. If you cannot identify what the door was tested with, our guide on how to identify a fire door explains where to find the label — often on the top edge or just below the bottom hinge.

What hinge faults do fire door inspections find most often?

Hinges are one of the most common sources of avoidable fire door failures, and most of the faults are visible without tools. When you carry out a fire door inspection — including the routine checks required by Regulation 10 on communal doors in higher-rise residential buildings in England — the hinges deserve a close look. The recurring problems are these.

None of these needs specialist equipment to spot, which is why hinges feature so heavily in inspection findings. The remedy is almost always the same: go back to the door's certificate and the manufacturer's schedule of tested hardware, replace with the specified part and the supplied fixings, and record what you did. Where a hinge fault sits alongside other problems — a failed self-closer, damaged seals, oversized gaps — treat the door as a whole rather than patching one component. Our guides to fire door self-closers and intumescent strips and smoke seals cover the neighbouring components.