FD30 is shorthand for a door assembly that demonstrated thirty minutes of integrity in a standard fire resistance test. The family runs upward in steps, and an S suffix adds smoke control. The number is a test result rather than a guarantee about a particular door in a particular building, and understanding the difference is what stops a rating being treated as a property of the leaf alone.
How the number is earned
A complete doorset is built as it is intended to be installed and exposed to a standardised heating curve in a furnace. Integrity is the point at which flame or hot gases pass through. The rating is the period the assembly survived, rounded down to the standard step. Because the whole assembly was tested, the rating describes the assembly, the frame fixings and the hardware alongside the leaf.
The S suffix
An S rating means the doorset also restricts the passage of cold smoke, tested separately, and in practice it means smoke seals in addition to intumescent. Smoke kills before flame does, and smoke control is required in specific locations such as doors onto protected escape routes and flat entrance doors. A door specified without the S where the guidance asked for it is a substantive shortfall, not a paperwork one.
Reading the marking
Certified doors carry a label or plug, usually on the top edge or the hinge edge, identifying the manufacturer, the certification scheme and the rating. That marking is the fastest route to knowing what a door is, and it is why a door with no marking and no documentation is treated as unknown rather than as compliant. Some schemes now use a marker readable with a scanner, linking to the certification record.
Higher ratings and where they appear
Longer periods appear where the element the door sits in demands it: compartment walls between different occupancies, plant rooms, service risers and some stair enclosures. A longer rating is not a general upgrade, because the door has to remain usable, and heavier doorsets create their own problems with closing forces and accessibility.
Questions people ask about fd30 fire door specification
What do fire door ratings uk buildings use mean in minutes?
The number is minutes of integrity in the standard test. Thirty and sixty minute doorsets are the common ones in occupied buildings, with longer periods in specific locations.
Is an FD30S door always needed on a flat entrance?
Flat entrance doors are a location where smoke control matters, and guidance for blocks of flats addresses them specifically. The building's own strategy and its age determine what is required.
Can a rating be established by inspection?
Not reliably. An inspection can find the marking, measure gaps and identify defects. Where there is no marking and no documentation, establishing the rating means investigation and sometimes replacement.