Understanding Fire Door Ratings: 20-Minute to 3-Hour Protection

In the UK, fire doors are classified by the number of minutes they can resist fire in a standard test. The "FD" prefix stands for "fire door," and the number that follows indicates the integrity period in minutes. FD30 doors provide 30 minutes of protection and are the most commonly specified rating for internal doors in residential and commercial buildings. FD60 doors offer 60 minutes and are required in higher-risk locations such as stairwell enclosures, lift lobbies, and certain industrial applications. FD90 and FD120 doors exist for specialist use in buildings with extended evacuation requirements.

The fire rating is determined through testing to BS 476 Part 22 or the European standard BS EN 1634-1. During the test, a door assembly (including frame, seals, and hardware) is exposed to a furnace that follows a standardised time-temperature curve. The door must maintain its integrity — meaning no flames or hot gases pass through — for the stated period. Some doors are also tested for insulation, indicated by an additional suffix, though integrity-only ratings are more common in the UK market.

Selecting the correct rating depends on the building's use, size, and the location of the door within the fire strategy. Approved Document B of the Building Regulations provides detailed guidance, but as a general rule: flat entrance doors require FD30S (with smoke seals), doors to protected stairways in buildings over 11 metres require FD60, and doors in hospital and care home corridors may need FD30 or FD60 depending on the ward layout. Always consult the building's fire strategy or a fire engineer when specifying fire door ratings.