Fire doors are one of the most important safety features in any building. They help slow the spread of fire and smoke, protect people and property, and give occupants crucial extra minutes to evacuate safely.
But to work effectively, fire doors need the right dimensions and thickness. Choosing the wrong size or using a door that doesn’t fit its frame properly can compromise fire safety.
In this guide, we cover everything you need to know about fire door sizes and thickness, including when a custom-size fire door is the best bet.
What are standard fire door sizes in the UK?
Standard fire door size varies depending on where in the UK your property is. Some of the most commonly specified sizes include:
- 1981 x 762 x 44mm. This is the most common internal fire door size in England and Wales.
- 1981 x 838 x 44mm. This is the most common internal door for spaces that require wheelchair access.
- 1981 x 726 x 44mm. This is the standard fire door size in Scotland, where doors tend to be slightly taller and narrower.
While these fire door dimensions are most common, they’re by no means the only options. You can find fire doors in a wide range of dimensions — and get made-to-measure doors, too.
Here is a wider selection of commonly available fire door sizes, with measurements in millimetres, inches and feet.
| Door sizes in mm — H x W | Door sizes in inches — H x W | Door sizes in feet and inches — H x W |
|---|---|---|
| 1981 x 457 mm | 78 x 18″ | 6’6″ x 1’6″ |
| 1981 x 533 mm | 78 x 21″ | 6’6″ x 1’9″ |
| 1981 x 610 mm | 78 x 24″ | 6’6″ x 2’0″ |
| 1981 x 686 mm | 78 x 27″ | 6’6″ x 2’3″ |
| 1981 x 711 mm | 78 x 28″ | 6’6″ x 2’4″ |
| 1981 x 762 mm | 78 x 30″ | 6’6″ x 2’6″ |
| 1981 x 838 mm | 78 x 33″ | 6’6″ x 2’9″ |
| 1981 x 915 mm | 78 x 36″ | 6’6″ x 3’0″ |
| 1981 x 1067 mm | 78 x 42″ | 6’6″ x 3’6″ |
| 1981 x 1168 mm | 78 x 46″ | 6’6″ x 3’10” |
| 1981 x 1220 mm | 78 x 48″ | 6’6″ x 4’0″ |
| 1981 x 1372 mm | 78 x 54″ | 6’6″ x 4’6″ |
| 1981 x 1524 mm | 78 x 60″ | 6’6″ x 5’0″ |
| 2040 x 626 mm | 80¼ x 24⅝” | 6’8¼” x 2’0⅝” |
| 2040 x 726 mm | 80¼ x 28⅝” | 6’8¼” x 2’4⅝” |
| 2040 x 826 mm | 80¼ x 32½” | 6’8¼” x 2’8½” |
What is the standard thickness of a fire door?
The thickness of a fire door plays a crucial role in its fire resistance. Standard thicknesses vary depending on the door’s construction materials and its FD rating.
While a regular, non-fire-rated door is usually around 35-40mm thick, fire doors are significantly thicker:
- FD30 (30 minute) fire doors: 44-45mm thick
- FD60 (60 minute) fire doors: 54mm thick
Doors with higher FD ratings can have a thickness of up to 64mm. Ultimately, the higher the fire rating, the thicker the door is likely to be.
What is the standard fire door frame size?
Standard fire door frame sizes are usually slightly larger than the door leaf itself. This allows for correct installation clearance and the fitting of intumescent strips.
Intumescent strips around the edges of the door expand in high temperatures to create a seal between the fire door and its frame. This prevents smoke or flames from passing through. (Learn more about how fire doors work.)
To allow space for these strips and ensure proper performance:
- The gap between the door and the frame along the top and vertical sides should be between 2 and 4mm.
- The gap along the bottom of the door should be no more than 10mm.
- If the fire door is designed to restrict both flames and smoke, the gap along the bottom of the door should be no more than 3mm.
Why are accurate fire door dimensions so important?
Even a high-quality fire door won’t do its job if it doesn’t fit the space or its frame properly. Small errors in fire door dimensions can have a big impact on fire safety.
If there are gaps around the door, smoke and flames can escape. If a door doesn’t close properly, it can’t create a fire-resistant seal.
Correct fire door sizing ensures your door performs properly in the event of a fire, meets its certified fire rating and complies with fire safety regulations. So you can be confident that it will keep people and your property safe.
How do you find the right fire door size?
It’s important to take precise measurements before installing a fire door. This guarantees that your door fits snugly, closes properly and meets UK fire safety standards.
To measure for a fire door, take three horizontal measurements and three vertical measurements within the door frame. Then, use the largest height and width to ensure a proper fit.
Alternatively, to be 100% confident that you’re getting a fire door that meets fire safety regulations, you can call in the experts.
Here at Fire Door Systems, our team of technicians conducts fire safety surveys, assessing fire doors, fire systems and fire safety procedures — and recommending the best-fit fire doors for a space.
When to choose custom size fire doors
Standard fire door sizes are suitable for most homes, offices and commercial buildings. But they’re not always the right fit.
You may need made-to-measure, custom size fire doors if any of the following apply:
- You have non-standard or irregular openings — older buildings, loft spaces and open plan spaces sometimes have unusual door dimensions
- You want double or half-leaf doors — in commercial and public buildings you may need double fire doors to ensure good traffic flow
- You need fire doors for a large industrial building — warehouses, factories and workshops often require oversized fire doors
Custom doors are also a good choice if you have special design requirements. As well as custom sizing, you can get a custom finish — so your fire door fits the aesthetics of your property.
Fire doors to fit any space from Fire Door Systems
At Fire Door Systems, we provide fire doors for every type of property and opening, from shops to hospitals, warehouses to homes. Our range includes:
- Timber fire doors. Stylish and durable doors, ideal for homes and offices.
- Steel fire doors. Secure, robust and perfect for commercial or industrial use.
- Glazed fire doors. Combining fire protection with natural light and visibility.
- Fire exit doors. Secure fire escapes for safe evacuation in an emergency.
We supply both standard-size fire doors and made-to-measure options. And our team of expert installers ensures the perfect fit. So your doors perform as intended, and you get total peace of mind.
Contact our team today to chat about your fire safety needs and find the right fire door solutions for your building.
Fire door sizes: FAQs
What is the standard size of fire doors?
The most common size of fire door in the UK is 1981 x 762 x 44mm. However, it’s important to take careful measurements when choosing a new fire door. If your fire door is slightly too big or too small, it won’t work properly in the event of a fire.
What is the standard fire exit door size?
Fire exit door size regulations depend on the age and usage of your building, as well as the width of your corridors. Fire exit doors should be a minimum of 800mm wide. They have to be wide enough to ensure that all building occupants can evacuate safely in an emergency.
Can you cut a fire door to size?
Yes, you can cut a fire door to size — but only according to strict tolerances.
You should never trim any material off the top of a fire door, as this is where essential fire door certification is located.
You may be able to trim the bottom and sides of a fire door if this is confirmed in manufacturer guidelines and test evidence. However, even in cases where trimming is allowed, you have to be extremely careful not to trim the door too much.
A fire door that is trimmed excessively may not provide the certified level of fire resistance and can leave your business non-compliant with fire safety legislation.
