Hinges are the least interesting component on a fire door and one of the most consequential. Nobody inspects a building and worries about hinges. They worry about closers, seals and certification labels.

Then you meet a door that somebody hung on two hinges four years ago. It has twisted far enough that the gap along its closing edge measures 7mm. The seals no longer touch the frame. Every other component on that door has been quietly defeated by the cheapest item in the assembly.

In this guide we will explain how many hinges a fire door needs. We cover what the grading actually certifies, and why the material matters. We also look at which defects inspectors record most often, and what the remedy looks like.

The Answer: Three, Minimum

A fire door needs a minimum of three hinges. BS 8214:2026 replaced the 2016 edition in March 2026. The code of practice reflects this, alongside the requirement that hinges carry UKCA or CE marking for the application.

Three is a floor rather than a target. Heavy leaves, wide leaves, glazed leaves and sixty-minute doorsets frequently need four, and the manufacturer’s instructions for the specific doorset decide it. A door that passed its fire test on four hinges needs four hinges to reproduce that test.

The practical arrangement places two hinges towards the top of the leaf and one towards the bottom, which puts the extra support where the load concentrates. The specification for the doorset sets the positions, and moving them is not a free choice.

Why Two Hinges Fail

The reason has little to do with fire and everything to do with geometry.

A fire door leaf is heavy. A 44mm FD30 leaf runs well over 25kg, and a 54mm FD60 leaf comfortably exceeds 40kg. Hang that mass on two points and the leaf rotates slightly around the axis between them. The top corner on the closing edge pulls in and the bottom corner pushes out, or the whole leaf sags away from the top hinge. Either way the leaf is no longer flat in the opening, and it is no longer parallel to the frame.

Now look at what that does to everything else. Head and jamb gaps need to sit between 2mm and 4mm. A twisted leaf produces a gap that is too tight in one place and far too wide in another, often on the same edge. Intumescent strips are specified to bridge a particular gap, and they cannot bridge a variable one. Smoke seals cannot stretch to reach a frame that has moved 5mm away from them. The latch may stop engaging cleanly because the keep is no longer where the leaf meets it. The closer has to work against a door that binds at one point and swings free at another.

Three hinges resist that rotation. That is the entire engineering argument, and it is why the requirement exists in a form that sounds arbitrary until you watch a two-hinge door age.

Weight also concentrates unevenly over time. Every use of the door applies a load, and a fire door in a communal corridor sees thousands of cycles a year. Two hinges wear faster because each carries more, which accelerates the drop.

What Grade 13 Means

Fire door hinges are graded under BS EN 1935, the European standard for single-axis hinges. The grading is what separates a fire door hinge from a hinge that merely looks like one.

Grade 13 is the specification you will see most often on fire doors. It certifies the hinge for heavy-duty use and rates it for doors up to 120kg, tested through a substantial number of cycles. Fire door hinges also carry certification for use in fire-resisting doorsets specifically. You will commonly see third-party approval such as Certifire alongside the CE or UKCA marking.

A typical fire door hinge measures 102mm by 76mm by 3mm, in stainless steel, with ball bearings. The ball bearings matter. They reduce friction and wear, which keeps the door swinging freely. A worn hinge is often the reason a closer cannot shut a door.

Two points catch people out. First, the 120kg rating applies to the door, not to each hinge. A heavy leaf can exhaust Grade 13 and need a higher specification or a fourth hinge. Second, the grade certifies the hinge in isolation, while the doorset’s certification covers the hinge as part of the tested assembly. Fitting a correctly graded hinge that was not part of the test still steps outside the certification.

Why the Material Matters

Fire door hinges are steel, almost always stainless steel, and the reason is simple: a hinge has to survive long enough to keep holding the door.

Brass and aluminium soften and lose strength at temperatures a developing fire reaches quickly. A brass hinge in a fire can deform enough to let the leaf drop out of the frame. At that point the door has failed completely, regardless of how well its core was performing. Decorative brass hinges on fire doors appear regularly in refurbished buildings. Somebody matched them to the ironmongery elsewhere without knowing what the door was.

Intumescent hinge pads add a second layer of protection where the tested specification calls for them. These sit behind the hinge blade, in the mortice. They expand in a fire to protect the recess, and restrict the path the cut-out creates through the leaf edge. They are easy to leave out during a hardware swap and they are part of the tested assembly where the specification includes them.

The Hinge Defects Inspectors Find

Six recur constantly.

Two hinges instead of three. Usually on doors hung before anyone checked, or on doors rehung during a refurbishment by a joiner working to domestic habits.

Missing screws. The most common hinge defect by a wide margin. A hinge fixed with three of its four screws carries less than it was graded for. The remaining screws take the difference until they work loose too. Every screw hole in a fire door hinge exists because the test had a screw in it.

The wrong material. Brass and aluminium hinges on fire doors, or mixed materials on a single leaf.

Mixed hinge types or sizes on one leaf. Different hinges load unevenly, which reintroduces exactly the twist that three hinges exist to prevent.

Missing intumescent pads. Where the specification required them and a hardware replacement left them out.

Worn hinges causing a dropped leaf. Not strictly an installation defect, but the endpoint of the others. The symptom appears on the survey as an excessive gap, and plenty of schedules record the gap without identifying the hinge as the cause.

That last point is worth dwelling on. When we inspect doors, a substantial share of the gap defects we record trace back to hinges rather than to the leaf. Re-lipping a door whose gap opened because the hinges have worn fixes the symptom for a year and then the problem returns.

What the Remedy Looks Like

Hinge defects are among the cheapest and fastest to correct, which makes them good value on any remedial programme.

Fitting the correct number of correctly graded hinges, with every screw, resolves most of them. Where screw holes have stripped, a joiner plugs and re-drills rather than moving to a longer screw. A dropped leaf often comes back into tolerance simply by rehanging on new hinges, with no work to the leaf at all. Where it does not, a new lipping follows, and this time it lasts because the cause has gone.

Adding a fourth hinge, where the doorset’s specification permits it, is the right answer on heavy leaves that keep dropping. Adding intumescent pads restores the tested assembly where they were omitted.

We handled hinge and hardware remedials as part of wider programmes at St James House in Maidenhead. We also specified hardware to match leaf weights on the new-build installation at the Chelsea FC training ground.

Frequently Asked Questions

How many hinges does a fire door need?

At least three. Heavy, wide, glazed and sixty-minute leaves often need four, and the doorset manufacturer’s instructions decide it. A door tested on four hinges needs four to reproduce that test.

Why do fire doors need three hinges instead of two?

Two hinges let a heavy leaf twist and sag. That opens the gap along the closing edge beyond the 2mm to 4mm tolerance, and pulls the seals away from the frame. Three hinges resist that rotation and keep the leaf flat in the opening.

Can you use brass hinges on a fire door?

No. Brass and aluminium soften at temperatures a fire reaches quickly, which can let the leaf drop out of the frame. Fire door hinges are steel, usually stainless, graded under BS EN 1935 and marked for fire use.

What does Grade 13 mean on a fire door hinge?

It is the BS EN 1935 classification for heavy-duty hinges rated for doors up to 120kg. The rating applies to the whole door rather than to each hinge, so a very heavy leaf may need a higher specification or an additional hinge.

Does a missing hinge screw really matter?

Yes. The hinge was graded and tested with every screw in place, and a hinge missing one carries less load than its rating describes. Missing screws are the most common hinge defect we record, and they lead directly to a dropped leaf.

Need Your Fire Door Hardware Checked?

At CFP Carpentry & Fire Prevention, we inspect fire door hardware against the tested specification and carry out remedial works including hinge replacement, rehanging and gap correction. Our joinery teams also handle timber door hanging across residential and commercial projects. We work for freeholders, managing agents, housing associations, main contractors and commercial building owners.

Get in touch today to arrange a fire door survey for your building.