Fire door ratings explained: FD30, FD30S, FD60 and FD60S

Fire doors are rated by how long they can hold back fire in a standard test. The rating is written as FD followed by the number of minutes, sometimes with an S.

The common ratings

• FD30: resists fire for 30 minutes.
• FD30S: resists fire for 30 minutes and also restricts the passage of cold smoke, thanks to smoke seals.
• FD60: resists fire for 60 minutes.
• FD60S: 60 minutes, with smoke seals.
• FD90 and FD120: used in special situations such as some plant rooms and protected shafts.

The S matters because smoke kills far more people in fires than flames do. A door can hold back fire for 30 minutes and still let enough smoke past to make a corridor impassable.

Where each is used

• Flat entrance doors in purpose-built blocks: usually FD30S, self-closing.
• Doors onto protected stairs and lobbies: usually FD30S, sometimes FD60S in taller buildings or where the fire strategy requires it.
• HMO bedroom and kitchen doors: usually FD30, often with self-closers.
• Riser and service cupboard doors: often FD30 or FD60, kept locked shut.
• Plant rooms and refuse stores: often FD60.

The building's fire strategy or fire risk assessment sets the rating needed for each door.

Is it a real fire door?

Signs of a genuine fire door include:

• a certification label or plug, usually on the top or hinge edge of the leaf
• intumescent strips and, for an S door, smoke seals in the frame or door edge
• at least three hinges
• a self-closing device where required
• fire-rated glazing with the correct beads, if glazed.

A door that looks heavy is not necessarily a fire door, and a fire door that has been altered, for example with a new letterbox or lock, may no longer perform as tested.

Keeping the rating

A fire door only performs as rated if it is installed and maintained as tested. Gaps that are too big, missing seals, damaged closers and wedges all undermine it. Our fire door inspection checklist covers what to check and how often.