FD30 vs FD60 Fire Doors: Certification, Furnace Testing and How They Protect You

What FD30 and FD60 mean

“FD” stands for fire door. The number is the minimum time, in minutes, that the door has been proven to stop fire and hot gases passing through it in a standard fire test. This is known as integrity.

• FD30: at least 30 minutes of integrity.
• FD60: at least 60 minutes of integrity.
• FD30S / FD60S: the same fire rating, plus smoke seals that limit the leakage of cold smoke around the edges of the door.

Those minutes are not about the door surviving. They are about buying time: time for people to get out along a protected escape route, and time for the fire and rescue service to arrive. In most homes, flats and HMOs, the first few minutes of smoke are the biggest danger, which is why smoke seals and self-closing devices matter as much as the rating itself.

FD30 vs FD60 side by side

The exact thickness, core, seal sizes and approved hardware always come from the manufacturer’s certificate for that specific product. Two FD30 doors from different manufacturers can be built quite differently and still both be correctly rated, because each one has its own test evidence.

Many manufacturers, one thing that counts

There are lots of fire door manufacturers in the UK, and fire doors can look very similar once they are painted and hung. What matters is not the brand name. It is the test evidence behind the door.

A fire door assembly only earns its 30 or 60 minute rating after it has been tested in a furnace and certified by an independent body such as Certifire. That certificate covers the exact door, frame, seals, glazing and hardware that were tested together. It is why a fire door must be fitted and maintained to match its certification, and why a door that simply looks the same as a fire door is not one.

When we supply and fit a fire door, the first thing we check is that its certification covers the opening, the glazing, the hardware and the way it will be used. If it does not, it is not the right door, whatever it costs.

How certification works

Third-party certification is independent proof that a fire door will perform as claimed. In the UK the best-known scheme is Certifire, run by Warringtonfire. Other recognised schemes include BM TRADA Q-Mark and IFC Certification, and the British Woodworking Federation’s Fire Door Alliance scheme, BWF-Certifire, is built on Certifire.

Certification bodies such as Certifire take a manufacturer’s fire door and:

1. Review the fire test evidence. The door design must have passed fire tests carried out at an accredited laboratory.
2. Define what is covered. The certificate sets out the sizes, glazing, intumescent seals, frames and types of hardware the rating applies to.
3. Audit the factory. Inspectors check the manufacturer’s production on an ongoing basis, so every door that leaves the factory matches the one that passed the test.
4. Make every door traceable. Certified doors carry a label or coloured plug, usually on the hinge edge or the top edge of the door, linking that door back to its certificate.

If the label or plug has been removed or painted over, it can be difficult to prove what a door is. That is one reason we always photograph and record certification details as part of our sign-off documentation.

Inside the furnace test

Fire doors in the UK are tested to BS 476-22 or the European standard BS EN 1634-1. The test is designed to be tough, and many designs fail it.

• The whole assembly is tested. The door leaf is hung in its frame, with its intumescent seals, any glazing, and its hinges, closer, lock and handles fitted, exactly as it would be on site.
• The heat climbs fast. The furnace follows a standard time and temperature curve. It passes about 840°C at 30 minutes and about 945°C at 60 minutes.
• The furnace pushes on the door. Pressure inside the furnace forces hot gases at the top of the door, where gaps are most likely to open.
• The cold side is watched closely. The door fails if flames appear on the unexposed face for more than a few seconds, if hot gases through a gap set fire to a cotton pad held against it, or if gaps open wide enough for gauges to pass through.
• Both faces matter. Doors are tested from the side that gives the hardest result, or from both sides, so the rating holds whichever side the fire starts.

A door that passes the full 30 minutes can be rated FD30. To be rated FD60 it has to keep going for the full hour, which is why FD60 doors are thicker and heavier, with more intumescent protection.

How a timber fire door protects you

It surprises many people that a timber door can hold back a fire for an hour. The secret is the way wood burns.

Charring slows the fire down

When flames hit the face of a timber fire door, the outer layer turns into char. That charcoal layer is a poor conductor of heat, so it insulates the timber behind it and slows the burn. Timber chars at a fairly steady and predictable rate, roughly 0.5 to 0.7mm a minute depending on the wood. This predictability is what allows manufacturers to design a door that will last 30 or 60 minutes in the furnace.

The other side stays cooler

Because the char layer protects the solid core behind it, the side of the door away from the fire stays far cooler than the side being burned. That is why the extra 10mm or so of thickness in an FD60 door, along with its denser core, makes such a difference: there is simply more material to char through before fire can break through.

Intumescent seals close the gaps

The weak points of any door are the gaps around its edges. Intumescent seals, fitted in the frame or the door edge, swell up when they get hot, at around 200°C. They expand to fill the gap between the door and the frame, stopping flames and hot gases getting through. Smoke seals, often combined in the same strip, deal with cold smoke in the early stages of a fire, before the heat builds.

Why the hardware matters

Hinges, closers, locks and latches are tested as part of the fire door assembly, so they are part of the rating. Steel and brass conduct heat, and the wrong hardware can melt, distort or let heat into the door, causing early failure.

Fire door hardware should be CE or UKCA marked to the relevant standard and fall within the scope of the door’s certificate:

• Hinges: BS EN 1935
• Door closers: BS EN 1154
• Locks and latches: BS EN 12209

A door that passed its furnace test with one type of hinge and closer is only proven with that type of hardware. Swapping parts for cheaper, unmarked or untested alternatives can mean the door no longer matches its certification. Our fire door hardware maintenance guide explains how to look after it.

Glazed fire doors: a second certificate

Many fire doors have a vision panel so people can see through them. The glass in a fire door is not ordinary glass, and it is not covered by the door certificate on its own. The glass and the system that holds it in place carry their own separate certification.

• Fire-rated glass only. Ordinary, toughened or laminated glass will shatter quickly in a fire. Fire-rated glass is tested to stay in place for the rated time. Some fire glass gives integrity only, while insulated fire glass also limits the heat passing through, which can be needed for larger panes or where people pass close to the door.
• A tested glazing system. The glass is held in with fire-rated glazing beads, intumescent glazing seals and fixings that were tested together with that glass. Swapping any of these for untested parts can void the rating.
• Within the door certificate. The door certificate sets the maximum size and position of the glazed opening, so a vision panel cannot simply be cut into any fire door.

That is why a glazed fire door comes with two certificates. After we install a glazed fire door, it is provided with sign-off documentation and certification for both the fire door assembly and the glazing system, so you have proof that the whole door, glass included, matches its test evidence.

Which rating do you need?

The rating you need is set by Building Regulations guidance (Approved Document B) and your fire risk assessment or fire strategy, not by preference. As a general guide:

• FD30 or FD30S is the most common rating in houses, flats and HMOs, including flat entrance doors and doors onto protected escape routes.
• FD60 or FD60S is usually needed where a longer period of protection is required, such as some plant and boiler rooms, stores, protected shafts and parts of larger or taller buildings.

Fitting FD60 where FD30 is required is not wrong, but it costs more and the extra weight needs hinges and closers to suit. Fitting FD30 where FD60 is required is a serious failure. If you are not sure, check your fire risk assessment or ask us to look at it with you.

Certification only works if it is fitted right

A certified fire door is only as good as its installation. The furnace test proves the design. The installer has to recreate that design in your building. Under BS 8214:2026, that means:

• fitting the door and frame as one certified fire door assembly, using components that are proven to work together
• keeping gaps within the limits on the certificate
• fitting the correct intumescent and smoke seals
• using only hardware covered by the certification
• sealing the gap between the frame and the wall with tested materials
• recording what was fitted, so it can be proven later

Our team is UK Fire Door trained and FireQual certified, with over 20 years’ experience. Every door we install is fitted to BS 8214:2026 and provided with sign-off documentation and certification. Find out more about our fire door installation service.