Fire doors explained: FD30 and FD60
A fire door is the one product in a house that is bought on a number almost nobody can define. The number is simple. What it attaches to is the part that catches people out, and it is the reason a certified leaf in the wrong frame is not a fire door at all.
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What is the difference between an FD30 and an FD60 fire door?
The number is minutes of fire resistance demonstrated in a standard test: FD30 for 30 minutes, FD60 for 60. FD30 leaves are usually 44mm thick and FD60 leaves 54mm. The rating belongs to the whole assembly, not the leaf alone, so frame, seals and ironmongery all count.
What does FD30 mean?
FD stands for fire door and the number is the period, in minutes, of fire resistance the doorset demonstrated under a standard fire test. FD30 means 30 minutes, FD60 means 60. The period is not how long the door survives in any real fire, which nobody can promise; it is a measured, repeatable classification that lets a specifier compare like with like.
In the UK, door assemblies are fire tested to a recognised standard — historically BS 476-22, and under the European method BS EN 1634-1, whose results are classified using codes such as E30 and EI30 rather than the FD prefix. [VERIFY: test standard and classification] — which standard and classification applies to a given door must be read from that door's own certification, not assumed.
FD30 vs FD60: how do they compare?
| FD30 | FD60 | |
|---|---|---|
| Fire resistance period | 30 minutes | 60 minutes |
| Typical leaf thickness | 44mm | 54mm |
| Weight | Substantially heavier than a standard 35mm door | Heavier again — hinge and frame specification matters more |
| Where it usually appears in homes | The common domestic requirement, including loft conversions and integral garages | Higher-risk separations, and where a designer or building control specifies it |
| Intumescent seals | Required as part of the tested assembly | Required, and typically to a larger specification |
What does the S in FD30S mean?
The S suffix denotes smoke control: the doorset is fitted with seals that restrict the passage of cold smoke around the leaf, in addition to the intumescent seals that deal with fire. Smoke kills earlier than fire does, and smoke seals are what stop a protected stairway filling before anybody uses it.
Where smoke control is required, an FD30 door without smoke seals does not satisfy it. [VERIFY: Approved Document B] — which doors require smoke seals in a given building is a design decision to confirm with building control, not one to take from a retail guide.
Why is the rating a property of the whole doorset?
This is the single most misunderstood thing about fire doors. What gets tested is an assembly: leaf, frame, intumescent and smoke seals, hinges, latch or lock, closer, and any glazing and beads. Change a component for one outside the scope of the test evidence and the assembly in front of you is no longer the assembly that passed.
- The leaf carries the core that resists the fire.
- The frame has to be suitable for the rating and fixed as the instructions require, because the leaf is only as good as what it closes against.
- Intumescent seals expand in heat and close the gap between leaf and frame.
- Smoke seals, where required, restrict cold smoke before the intumescent has activated.
- Hinges, latches and closers must be suitable for the doorset and fitted as specified. Ironmongery is part of the assembly, not an accessory to it.
- Glazing must be fire-rated glass in a tested bead and glazing system, not ordinary glass in a fire door.
How do I know a fire door is what it says it is?
Certified fire doors are marked, and the marking is how the door is identified after it is fitted and painted. Look for identification on the door itself and keep the paperwork that comes with it — the certification, the installation instructions, and the details of the seals and ironmongery it was tested with. Building control, an insurer or a future buyer may all want to see it.
Common questions
What does FD30 mean on a door?
It means the doorset demonstrated 30 minutes of fire resistance under a standard fire test. FD is fire door and 30 is the period in minutes. FD60 is the same classification at 60 minutes.
How thick is an FD30 fire door?
FD30 leaves are usually 44mm thick, against 35mm for a standard internal door, because of the dense core that provides the fire resistance. FD60 leaves are usually 54mm. Always check the specific door, as thickness is part of the tested specification.
What is the difference between FD30 and FD30S?
The S denotes smoke control. An FD30S doorset carries seals that restrict the passage of cold smoke around the leaf, as well as the intumescent seals that deal with fire. Where smoke control is required, an FD30 without smoke seals does not meet it.
Do fire doors need intumescent strips?
Yes. Intumescent seals expand in heat to close the gap between the leaf and the frame, and they are part of the assembly that was tested. A fire door without the seals it was tested with does not perform as certified.
Can I use ordinary hinges on a fire door?
No. Hinges are part of the tested assembly and must be suitable for the doorset and fitted as the manufacturer specifies. The same applies to latches, locks and closers. Substituting ironmongery outside the test evidence invalidates the rating.
Is a fire door the same as a fire-resistant door?
In everyday use, yes, but the meaningful term is the rating. A door described loosely as fire resistant, with no rating, no certification and no test evidence behind it, tells you nothing you can rely on or show to building control.
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Every door lists its sizes in both imperial and metric, so you can check yours against what you measured before you commit.