FD90 and FD120 are both certified fire doorsets, rated to resist fire for at least 90 and 120 minutes of integrity respectively (broadly Per certified design and Per certified design under BS EN 13501-2). The difference is duration: FD120 holds the line for 120 minutes where FD90 holds it for 90. FD90 is specified for high-hazard compartmentation, significant compartment lines and industrial positions; FD120 for major compartment walls, basements and high-hazard storage and process areas. The correct rating for any opening comes from the building's fire strategy and risk assessment, not a general rule.
FD90 vs FD120 at a glance
| FD90 | FD120 | |
|---|---|---|
| Fire resistance | 90 minutes | 120 minutes |
| EN classification | Per certified design | Per certified design |
| Typical leaf | Per certified design | Per certified design |
| Where it is specified | high-hazard compartmentation, significant compartment lines and industrial positions | major compartment walls, basements and high-hazard storage and process areas |
When FD90 is the right choice
Specify FD90 where the fire strategy calls for 90minutes' integrity — high-hazard compartmentation, significant compartment lines and industrial positions. Stepping up to a higher rating than the strategy requires adds cost and weight without adding compliance; the rating should match the assessed risk at each opening.
When to step up to FD120
FD120 is specified where the fire strategy or Approved Document B demands 120 minutes rather than 90 — major compartment walls, basements and high-hazard storage and process areas. At this rating the doorset construction is heavier and, above FD60, the design and glazing become more restricted; confirm what is achievable against the certified field of application.
Both figures describe integrity (E) — resisting flame and hot gases — not insulation (EI), which limits heat transfer and is separately tested. Leaf thicknesses are typical, not mandatory; the certified design governs. Also see FD30 vs FD60, the full range (FD30–FD120), or run the compliance checker.