Quick answer. A fire door is not a product, it is a tested doorset: the leaf, frame, hardware and seals are qualified together. In the US, NFPA 80 limits clearances to 1/8 in (≈3.2 mm) at the top and side edges for wood doors, up to 3/16 in (≈4.8 mm) for metal doors and 3/4 in (≈19 mm) at the bottom. In EU/UK practice the doorset is qualified by test under BS EN 1634-1 (current: 2014+A1:2018) or BS 476-22.
Fire door clearances and test standards at a glance
| Item | Figure | Source |
|---|---|---|
| Top and side edge clearance, wood doors | ≤ 1/8 in (≈3.2 mm) | NFPA 80 (US) |
| Top and side edge clearance, metal doors | ≤ 3/16 in (≈4.8 mm) | NFPA 80 (US) |
| Bottom clearance | ≤ 3/4 in (≈19 mm) | NFPA 80 (US) |
| Doorset fire resistance test (EU/UK) | EN 1634-1:2014+A1:2018 | Current European reference |
| Older British doorset test | BS 476-22 (1987) | Being phased out from 2029 |
| Kenya standard series | KS 3050-1:2026 published; Part 2 in draft | KEBS webstore |
1. The door that looked like a fire door
A steel leaf, three hinges, a closer, a rating label someone remembers seeing. It looks like a fire door. But on the day it matters, the smoke does not care how thick the steel is. It cares about the gaps.
In a building, a stairwell is both the escape route and a vertical shaft. Hot smoke rises through it — the same stack effect that makes a chimney work. A doorset that closes but does not seal is a doorway for smoke long before it is a doorway for flame.
2. Why the rules are about the doorset, not the leaf
This is, in our experience, one of the most misunderstood points in the trade: a fire door is not a product, it is a tested assembly. The leaf, the frame, the hinges, the lock, the closer, the threshold and the seals are qualified together.
In the British/European route that East African projects generally use, a fire-resisting doorset is subjected to BS 476 Part 22 (1987) or to BS EN 1634-1; the latest European reference is EN 1634-1:2014+A1:2018.
The report that comes out of that test is not a certificate of “quality”. It records constructional details, distortion data and pressure readings — in other words, exactly which assembly was tested, and how it behaved.
3. Where the numbers come from
Buyers often ask “how big a gap is allowed?” One of the clearest published answers comes from NFPA 80 in the United States: at the top and side edges, clearances must not exceed 1/8 in (≈3.2 mm) for wood doors, and up to 3/16 in (≈4.8 mm) for metal doors; at the bottom, the clearance must not exceed 3/4 in (≈19 mm). Always verify against the edition your project names.
In EU/UK practice the logic is slightly different: rather than publishing one gap number for every door, the doorset is qualified by test — the specimen’s gaps and seals are part of the tested assembly, and the report describes what was tested.
4. Three seals, three jobs
An intumescent strip expands when exposed to heat, sealing the gap as the fire develops. A smoke gasket seals cold smoke at ambient temperature — before anything intumesces. Neoprene or weatherstrip handles draught, weather and acoustics, and is not a fire seal by itself.
Crucially, intumescent products are not one material. They differ in chemical composition, expansion rate and expansion volume. That is why “the door has an intumescent strip” proves nothing by itself: the data sheet is the evidence.
Two details get forgotten even when the seals are right. The gap between the frame and the wall must be filled with fire-resisting material, not simply expanding foam. And seals must not be painted over or removed during refurbishment.
5. Five checks a dealer can run on site
1) Measure the edge gaps with a feeler gauge — top, both sides, and both corners.
2) Look at the bottom. Is there a threshold or an automatic drop-down seal, or a gap you can see daylight through?
3) Read the report’s scope, not just its cover: standard and version (EN 1634-1:2014+A1:2018 / BS 476-22 / UL 10B or 10C), the rating (EI₂ 30/60/120), the maximum tested size, and whether frame, hardware and seals were included.
4) Ask for the intumescent strip’s data sheet: composition, expansion rate, expansion volume — and whether it is the same product that was in the tested doorset.
5) Check the frame-to-wall joint and the seal condition: filled with fire-resisting material, not painted over, not missing.
6. What this means in Kenya and Tanzania
Kenya: the KS 3050 series is still forming. KS 3050-1 is published and on sale in the KEBS webstore (KS 3050-1:2026), while Part 2 remains in draft — a window in which projects specify what they know.
Two practical consequences: the Chinese standard GB 12955 is generally not accepted on East African projects; and the BS 476 series is being phased out from 2029, so EN 1634-1 is the safer language to work in.
Tanzania: EN 1634-1 certified doorsets have already been supplied to projects there, which tells you which certification language the market reads.
7. What we do, and what we will not claim
Our fire-rated steel doors are produced to EN 1634-1 tested configurations, and we can provide the report package (report + doorset scope + hardware list + installation manual) with the quotation. If a project requires a specific local approval (KS 3050 in Kenya, TBS in Tanzania), tell us and we will confirm the applicable route.
We will not invent report numbers, and we will not describe a leaf as “certified” when the tested assembly is what carries the rating.
Next step: send us the project’s requirement — rating, sizes, quantity, city — and we will come back with the tested configuration and documentation list. → WhatsApp / enquiry form
8. Sources — and what we deliberately left out
BS 476-22 (1987) and BS EN 1634-1 (current: 2014+A1:2018) — doorset fire resistance tests and report contents; NFPA 80 — published door clearance limits (1/8 in top and side edges for wood, up to 3/16 in for metal, 3/4 in at the bottom); intumescent materials — expansion behaviour and the fact that composition, expansion rate and expansion volume differ between products; KS 3050-1:2026 (published, KEBS webstore) with Part 2 in draft; BS 476 series phase-out from 2029.
Frequently asked questions
How big a gap is allowed around a fire door?
NFPA 80 in the United States publishes the clearest figures: no more than 1/8 in (≈3.2 mm) at the top and side edges for wood doors, up to 3/16 in (≈4.8 mm) for metal doors, and no more than 3/4 in (≈19 mm) at the bottom. Always check the edition your project names — and in EU/UK practice the gap forms part of the tested doorset rather than a single published number.
What is the difference between an intumescent strip and a smoke seal?
An intumescent strip expands when heated and seals the gap as a fire develops. A smoke gasket seals cold smoke at ambient temperature, before anything intumesces. Neoprene or a weatherstrip handles draught, weather and acoustics — it is not a fire seal by itself.
Is GB 12955 accepted on East African projects?
GB 12955 is the Chinese national standard and is generally not accepted on East African projects. EN 1634-1 is the working certification language in the region; in Kenya, KS 3050-1:2026 is published and Part 2 is still in draft. The BS 476 series is being phased out from 2029, so EN 1634-1 is the safer route for new projects.
Does a fire door need a threshold or bottom seal?
The bottom gap is regulated like the others, so it has to be controlled — either by a threshold, an automatic drop-down seal, or by keeping the clearance within the tested limit. What matters is that the arrangement is the one that was tested.
Why JinHong Doors
We have 39 years of door manufacturing experience in China and are now exporting to East and African markets — steel security doors, fire-rated doors and project doors. We quote with the specification sheet, packing plan and the documentation your project asks for.
Request the tested configuration and document list →
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Also read: why the same powder-coated door fails at the coast →
