Fire Door Sizes: A Complete UK Guide to Dimensions and Thickness
Fire doors are a legal requirement in many UK buildings. Yet, choosing the wrong size remains one of the most common compliance mistakes. According to the Fire Door Inspection Scheme (FDIS), 72% of fire doors did not meet the required standard to pass inspection in 2025. Excessive gaps, smoke sealing problems, and poor maintenance were among the most common issues.
This guide covers what a fire door is, standard UK fire door sizes in both imperial and metric, thickness requirements for FD30 and FD60 ratings, accessibility considerations, how to measure for a fire door, and trimming rules. Use it to find the right fire door dimensions for your specific project.
What is a Fire Door?
A fire door is a specially constructed door designed to resist the spread of fire and smoke between compartments of a building for a set period, typically 30 or 60 minutes. It forms part of a building’s passive fire protection system, allowing safe evacuation and helping firefighters contain the blaze.
Fire doors differ from standard internal doors in several key ways. They use fire-resistant core materials such as solid timber, engineered composites, or steel. They are significantly thicker (44mm compared to 35mm for standard doors). They also include intumescent strips that expand under heat to seal the gap between the door and the frame.
Fire doors carry certification labels, usually found on the top edge. These labels show the fire rating and test standard (BS 476 or BS EN 1634).
Standard Fire Door Sizes in the UK
UK fire door sizes follow standard internal door dimensions, but with increased thickness to meet fire rating requirements. There are two main size systems used in the UK: imperial (common in England and Wales) and metric (increasingly popular in Scotland and Europe).
Imperial Fire Door Sizes
The standard imperial fire door sizes available in the UK cover a range of widths at a fixed height of 1981mm and a thickness of 44mm for FD30-rated doors. Here are the most common options and where each is typically used.
| Size (mm) | Imperial equivalent | Typical use |
|---|---|---|
| 1981 x 457 x 44 | 78″ x 18″ | Cupboard and wardrobe doors |
| 1981 x 533 x 44 | 78″ x 21″ | Small cupboard or storage doors |
| 1981 x 610 x 44 | 78″ x 24″ | Restricted wall space or smaller openings |
| 1981 x 686 x 44 | 78″ x 27″ (2′6″) | Bathrooms and utility rooms |
| 1981 x 762 x 44 | 78″ x 30″ (2′6″) | Most common internal fire door size in England and Wales |
| 1981 x 838 x 44 | 78″ x 33″ (2′9″) | Wheelchair access (Part M compliant) |
The 1981 x 762mm door is the most widely used fire door size in residential properties across England and Wales. If your property needs wheelchair access, choose the 838mm width to meet Part M mobility requirements.
Metric Fire Door Sizes
Metric fire door sizes are increasingly standard in Scotland and across Europe. The main difference from imperial sizes is an increased door height of 2040mm (compared to 1981mm) and a standard thickness of 40mm or 44mm.
| Size (mm) | Imperial equivalent | Typical use |
|---|---|---|
| 2040 x 526 x 44 | 80″ x 20.7″ | Cupboard doors |
| 2040 x 626 x 44 | 80″ x 24.6″ | Small openings |
| 2040 x 726 x 44 | 80″ x 28.6″ | Standard Scottish internal door |
| 2040 x 826 x 44 | 80″ x 32.5″ | Wider residential openings |
| 2040 x 926 x 44 | 80″ x 36.5″ | Commercial use and wide access |
Metric sizes are becoming more popular across the UK, especially in new-build developments where taller doors give rooms a more contemporary feel.
Fire Door Sizes Conversion Chart (mm to inches)
If you work in feet and inches, this conversion chart covers all common fire door sizes in both imperial and metric height ranges.
| Metric (mm) | Imperial (inches) | Imperial (feet and inches) |
|---|---|---|
| 1981 x 457 | 78″ x 18″ | 6′6″ x 1′6″ |
| 1981 x 533 | 78″ x 21″ | 6′6″ x 1′9″ |
| 1981 x 610 | 78″ x 24″ | 6′6″ x 2′0″ |
| 1981 x 686 | 78″ x 27″ | 6′6″ x 2′3″ |
| 1981 x 762 | 78″ x 30″ | 6′6″ x 2′6″ |
| 1981 x 838 | 78″ x 33″ | 6′6″ x 2′9″ |
| 2040 x 526 | 80″ x 20.7″ | 6′8″ x 1′8.7″ |
| 2040 x 626 | 80″ x 24.6″ | 6′8″ x 2′0.6″ |
| 2040 x 726 | 80″ x 28.6″ | 6′8″ x 2′4.6″ |
| 2040 x 826 | 80″ x 32.5″ | 6′8″ x 2′8.5″ |
| 2040 x 926 | 80″ x 36.5″ | 6′8″ x 3′0.5″ |
This chart covers both imperial (1981mm height) and metric (2040mm height) ranges. Always double-check your measurements against the frame before ordering.
How Thick Is a Standard Fire Door?
Standard internal doors are typically 35mm thick. Fire-rated doors must be significantly thicker to accommodate fire-resistant core materials. The thickness directly determines how long the door can withstand fire penetration. A door that does not meet the correct thickness for its rating is non-compliant and will fail during a fire.
Here are the main thickness standards based on fire rating.
| Fire rating | Minimum thickness | Typical use |
|---|---|---|
| FD30 (30 minutes) | 44mm | Residential properties, flats, loft conversions |
| FD60 (60 minutes) | 54mm | Commercial buildings, high-rise flats, kitchens, plant rooms |
| FD90 (90 minutes) | 64mm | High-risk commercial and industrial settings |
| FD120 (120 minutes) | 68mm | Specialist industrial environments |
FD30 doors at 44mm thick are the most common choice for homes. Higher ratings like FD90 and FD120 are used in specialist commercial or industrial settings where longer evacuation times are needed.
What is the Difference Between FD30 and FD60 Fire Doors?
FD30 and FD60 are the two most common fire door ratings in the UK. The number refers to how many minutes the door can resist fire. Here is a side-by-side comparison.
| Feature | FD30 | FD60 |
|---|---|---|
| Fire resistance | 30 minutes | 60 minutes |
| Typical thickness | 44mm | 54mm |
| Approximate weight | 25 to 45 kg | 50 kg and above |
| Cost | Lower | Considerably higher |
| Common use | Houses, flats, loft conversions, garage-to-house doors | Commercial buildings, high-rise flats, kitchens, plant rooms |
For most residential projects, FD30 doors provide the required level of protection. FD60 doors are typically specified by building regulations for commercial properties and higher-risk areas.
Fire Door Sizes for Different Applications
The correct fire door size depends on where it will be used. Here is what to expect for residential, commercial, and accessible settings.
Residential Fire Door Sizes
In houses with loft conversions (3 or more storeys), fire doors are required on every habitable room that opens onto the stairwell. Doors from an integral garage into the house must also be fire-rated.
Standard residential fire door sizes are typically 1981 x 762 x 44mm or 1981 x 838 x 44mm. For cupboards and wardrobes that require fire protection, narrower sizes like 1981 x 457mm or 1981 x 533mm are used.
Commercial and Industrial Fire Door Sizes
High-traffic areas such as hospitals, schools, and offices often need wider doors (838mm or wider) to accommodate equipment, trolleys, and higher footfall. Metric sizes like 2040 x 926mm are common in commercial new builds.
Industrial facilities such as warehouses may need bespoke oversized fire doors. Double-leaf fire doors can provide openings up to 1200mm wide or more, depending on the requirements.
Accessible Fire Door Sizes for Wheelchair Access
Under Part M of the Building Regulations, doors providing access for wheelchair users must offer a clear opening width of at least 850mm. This typically requires a door leaf width of 838mm (2′9″) or wider.
In public buildings and new-build residential properties, accessibility-compliant fire doors should be standard practice. The clear opening is measured when the door is open at 90 degrees, so the frame width must be factored in.
How to Measure for a Fire Door?
Getting the measurements right is critical. Incorrect sizing can compromise the fire rating entirely. A door that is too small leaves gaps that allow smoke and fire to pass through. A door that is too large may not close properly. Follow these steps.
First, measure the frame width at three points: top, middle, and bottom. Use the smallest measurement. Next, measure the frame height at three points: left, centre, and right. Again, use the smallest measurement.
Then, measure the existing door thickness or check the frame depth. Allow for correct gap clearances: 2 to 4mm on the top and sides for intumescent seals, and the maximum gap specified by the manufacturer at the bottom.
If you are unsure about any measurement, consult a professional or the door supplier before ordering. Getting it wrong means the door may not meet its fire rating, which puts your property at risk.
Can You Cut or Trim a Fire Door to Size?
Yes, fire doors can be trimmed, but only within very strict limits. Most manufacturers allow trimming of 3 to 5mm per edge, depending on the product. Going beyond these limits can completely invalidate the door’s fire rating.
The certification label is usually located on the top edge of the door. Trimming the top is generally not permitted, as it would remove the certification. Over-trimming is one of the most common defects found by fire door inspectors.
Always check the manufacturer’s trimming allowance before cutting. Keep documentation as proof of compliance. If the door needs more than minor trimming, a bespoke or made-to-measure fire door is the safer option.
Fire Door Frame Sizes and Gap Requirements
Standard fire door frame sizes in the UK are 108mm and 133mm in thickness. The gap between the door leaf and the frame should be between 2mm and 4mm on the top and sides. The gap at the bottom should not exceed the threshold specified by the manufacturer.
Gaps larger than 4mm allow smoke and fire to pass through, defeating the purpose of the fire door. The Fire Safety (England) Regulations 2022 guidance states that the industry standard gap size should never exceed 4mm, except at the bottom.
When do you Need a Custom or Bespoke Fire Door?
Standard fire door sizes do not suit every property. You may need a bespoke fire door if you have period properties with non-standard openings, commercial buildings with oversized doorways, specialist environments like hospitals or schools, or renovation projects where existing frames do not match standard dimensions.
Bespoke fire doors can be manufactured to exact specifications and can achieve the same fire ratings (FD30, FD60, and higher) as standard doors. Some steel bespoke doors can provide up to 4 hours (FD240) of fire protection. Bespoke options are more expensive and typically have longer lead times.
Emerald Doors offers a full range of custom made fire doors built to your exact measurements. Every door is certified to the required fire rating, so you get the right fit without compromising on safety.
Find the Right Fire Door Size with Emerald Doors
Choosing the correct fire door size is essential for both legal compliance and genuine safety. Standard UK sizes follow imperial (1981mm height) and metric (2040mm height) dimensions. Thickness must match the fire rating: 44mm for FD30 and 54mm for FD60. Gaps must stay within 2 to 4mm. Trimming must remain within manufacturer limits.
Emerald Doors is a trusted UK supplier of certified fire doors in a wide range of standard and custom sizes. With over 20 years of expertise, a 10-year guarantee against manufacturing defects, and most orders delivered within 3 to 5 days, we make it simple to find the right fire door for your project.
FAQs about Fire Door Dimensions
Here are answers to some of the most common questions about fire door sizing in the UK.
What is the Most Common Fire Door Size in the UK?
The most common fire door size in England and Wales is 1981 x 762 x 44mm, also known as a 2′6″ door. In Scotland, the metric equivalent of 2040 x 726 x 44mm is more widely used.
How Heavy is a Standard Fire Door?
A standard FD30 fire door typically weighs between 25 and 45 kg, depending on the material and size. FD60 fire doors are heavier, often exceeding 50 kg due to their thicker, denser core.
Can I use a Standard Door Frame with a Fire Door?
No. A fire door must be fitted into a fire-rated frame with the correct intumescent seals and gap tolerances (2 to 4mm on the top and sides). Using a standard frame compromises the fire rating and leaves your property non-compliant.