FD30 vs FD60: fire door ratings explained

If you have looked at a fire door specification, you will have seen codes like FD30, FD60 and FD30S. They are not arbitrary. Each one tells you how long the door assembly is designed to resist fire, and whether it also controls smoke. Understanding them helps you check that the right door is in the right place, which is one of the things an inspection confirms.

What the FD number means

FD stands for fire door. The number is the rating in minutes of fire resistance the door assembly achieved under test conditions.

• FD30 resists fire for at least 30 minutes
• FD60 resists fire for at least 60 minutes
• FD90 and FD120 resist for 90 and 120 minutes respectively, used in more demanding situations

The rating applies to the whole assembly as tested, leaf, frame, seals and hardware together, not to the leaf in isolation. This is why fitting non-matching components or modifying a door can invalidate its rating.

What the S suffix means

An S after the number, as in FD30S, means the door also has a cold smoke seal and is tested to limit the spread of smoke at ambient temperatures, not just the spread of fire. Smoke is what incapacitates and kills people in most fires, often well before flame reaches them, so smoke control is frequently as important as fire resistance.

A plain FD30 controls fire for 30 minutes. An FD30S controls fire for 30 minutes and restricts cold smoke from the outset.

Where each rating is used

The right rating depends on the building, its layout and its fire strategy, which is determined by a competent fire engineer or risk assessor rather than chosen by default. As a general picture:

• FD30 and FD30S are common for flat entrance doors and many internal compartment and corridor doors in residential and commercial buildings
• FD60 and FD60S are used where greater separation is needed, for example protecting longer escape routes, plant rooms, or higher-risk compartments, and in taller buildings

Crucially, you cannot tell the required rating simply by looking. It comes from the building's fire strategy and risk assessment. An inspection checks that the door present matches what the building requires.

How ratings relate to gaps and seals

A door's rating is only meaningful if the assembly is maintained as certified. Two things in particular tie back to the rating:

• Gaps. The clearance around the leaf must stay within tolerance, usually around 3mm. Excessive gaps let fire and smoke bypass the door regardless of its rating. Our guide on fire door gaps explains the tolerances.
• Seals. Intumescent seals expand in heat to close the perimeter gap. Smoke seals handle cold smoke. A door rated FD30S with painted-over or missing seals is no longer delivering the performance its label claims.

This is the heart of inspection: confirming that the door on site still matches the certified assembly its rating is based on, against a standard such as BS 8214.

Reading a door's label

Certified fire doors usually carry a label or plug, often on the top or hinge edge of the leaf, identifying the manufacturer and the rating. During registration and inspection, that information is recorded so the door's identity and certification travel with it through its whole life, supporting the golden thread of building safety information.

How DoorTRACE helps

DoorTRACE records the fire rating, certification reference and key details of every door at registration, so the right specification is captured once and checked against at every inspection. If a door's condition drifts from its rating, it is flagged as a defect and tracked to resolution. Explore the platform or book a demo.