The choice between an FD30 and an FD60 fire door looks like a simple one: more minutes must be better. It is not that simple. The rating is a tested performance duration, and fitting a higher rating than the building calls for does not automatically make you more compliant. Specify the wrong door in either direction, and you can end up with a heavier, costlier door that still fails to match the building’s fire strategy.

This guide explains what the two ratings actually mean, how they differ in the flesh, where each belongs, and how to make the call with confidence.

What FD30 and FD60 actually mean

Start with the label. FD stands for fire door, and the number is in minutes. An FD30 door is an assembly tested and certified to hold back fire for at least 30 minutes; an FD60 is the same test run to 60 minutes. The number is a duration, not a material and not a thickness.

That distinction matters more than it sounds. A 54mm door does not automatically carry any particular rating, and a 44mm door can perform to FD30 if the whole assembly was tested to do so; the rating is earned by a physical test to BS 476-22 or BS EN 1634-1, not by measuring the leaf. In practice, that means only a tested, certified doorset can be relied on to confirm fire-resistance performance — the paperwork proves the door, the tape measure does not.

The physical differences at a glance

Although thickness never defines the rating, it is a useful sanity check. FD30 doors are usually 44 to 45mm thick and FD60 doors normally 54mm, against 35 to 40mm for a standard internal door. A door significantly under 44mm is unlikely to be a genuine fire door, and warping or over-planing can quietly drop a leaf below its certified minimum, so measure at several points.

The extra material in an FD60 is not just thickness.FD60 doors reach their performance through higher-density cores and enhanced intumescent systems, can exceed 75kg, and therefore demand robust frames, hinges and fixings. The heavier leaf is often cited as up to around 25% heavier than the FD30 equivalent, and FD60 doors typically need wider intumescent seals, which must be continuous, undamaged, and never painted over.

Feature	FD30	FD60
Fire resistance (tested)	30 minutes	60 minutes
Typical leaf thickness	44 to 45mm	54mm
Weight	Lighter	Heavier (often ~25% more; can exceed 75kg)
Core	Solid core	Higher-density core
Frame and ironmongery	Standard fire-rated	Heavier-duty, enhanced spec
Most common use	Domestic and lower-risk	Commercial and higher-risk

Figures are typical, not mandatory. UK regulations set no absolute minimum thickness; the door has to pass the test for its rating.

The “S” suffix: fire is not the same as smoke

You will often see FD30S or FD60S. The “S” means the door also resists the passage of cold smoke, using smoke brushes or seals on top of the intumescent strips. The two systems do different jobs at different moments. Intumescent strips expand at roughly 200 degrees Celsius to seal against flame, while cold-smoke seals block the toxic smoke that moves through gaps long before the strips activate. Since smoke, not flame, causes most fire deaths, the S rating is frequently specified on doors protecting escape routes, whether the leaf is FD30 or FD60.

Where FD30 is the right call

FD30 is the workhorse of UK fire doors. It is the most commonly specified rating, while FD60 is most common in commercial settings. In domestic property, the triggers are well defined: in a two-storey house, a door from an integral garage into the house must be a fire door, and homes of three storeys or more, including loft conversions, must have FD30 doors to every habitable room off the stairwell.

In flats and shared buildings, FD30 also does much of the work. Approved Document B calls for fire doors on escape routes and, in flats above 4.5m, FD30 doors dividing each flat from communal areas such as stairways, corridors and lobbies. FD30 and FD30S doors are the usual choice where the fire strategy needs 30 minutes: many flat entrance doors, often FD30S, plus doors onto protected corridors and stair and lobby doors.

Where FD60 is required

FD60 earns its place where escape takes longer, or the risk is higher. It is used in commercial and high-rise residential buildings that take longer to evacuate, and where a fire door sits in a compartment wall between separate buildings, it should provide a minimum of 60 minutes. Typical FD60 applications include protected escape stairs in high-rise buildings, plant rooms, electrical switchrooms, and other high-risk areas, and the rating brings an enhanced specification, such as heavy-duty certified hinges.

Some sectors lean on FD60 heavily. Healthcare buildings often specify it throughout because evacuation is frequently horizontal, moving patients to an adjacent compartment rather than out of the building, so the extra 30 minutes is critical.

Why bigger is not automatically better

Here is the trap. Because FD60 sounds safer, it is tempting to over-specify and assume you are covered. Fitting an FD60 where FD30 is required does not automatically improve compliance; the door still has to match the building’s fire strategy and its tested certification, and over-specification without evidence or compatibility can itself be non-compliant.

There are practical costs too. FD60 doors are generally more expensive and need more robust frames and ironmongery, and changing a rating up or down without professional guidance is unwise because the rating is part of the building’s overall fire safety design. A heavier leaf also loads hinges and closers harder, so an over-specified door that is not matched to the right frame and hardware can perform worse in service, not better.

How to choose the right rating

The decision is not yours to make on instinct. Selecting the rating is a strategic decision dictated by the building’s fire risk assessment, not personal preference. That assessment should specify the required rating for each location, and the doors installed should be compared against it; if doors have been swapped without reference to the assessment, there is a real chance the wrong rating is fitted.

Once you know the rating, get the specification right at purchase. Thickness must match the rating, perimeter gaps should stay within 2 to 4mm, and any trimming must stay inside the manufacturer’s certified limits. Where a standard size will not fit, bespoke fire doors can be made to exact dimensions and still achieve FD30, FD60 or higher, which is safer than trimming a stock leaf beyond its limits on site. And getting it right at source matters: FDIS inspection data found around 75% of UK fire doors failed to meet the required standard, with roughly 31% of failures caused by improper installation.

Quick decision checklist

• Check the fire risk assessment first: it names the rating required at each opening.
• Confirm whether smoke control is needed, which points to an S-rated door (FD30S or FD60S).
• Default to FD30 for domestic and lower-risk internal openings unless the strategy says otherwise.
• Specify FD60 for high-rise escape stairs, compartment walls between buildings, plant and switch rooms, and higher-risk commercial or healthcare settings.
• Do not over-specify to feel safe: match the tested, certified system rather than guessing upward.
• Buy certified doorsets, keep the documentation, and order bespoke sizes rather than trimming beyond certified limits.
  

The bottom line

FD30 versus FD60 is not a contest where the bigger number wins. FD30 is the correct, compliant choice for most domestic and lower-risk openings; FD60 is essential where evacuation takes longer, or the risk is higher. The right answer for any given door is written in the building’s fire risk assessment and its fire strategy, backed by a tested, certified product and correct installation.

Q Doors supplies certified FD30 and FD60 fire doors and complete doorsets, manufactured in the UK with certification documentation for every product and bespoke sizing available. Match the rating to your fire strategy, and we will supply the certified door to suit.