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This is why we’ve put together this guide, answering all the commonly asked questions about external door sizes. From knowing what a standard door size is, to the legal requirements and the words you need to know when measuring your external doors, we’ve got all the information you need to make sure you get the right sized door for your home.

Questions about External Door Sizes

What Are Standard Door Sizes for External Doors?

External doors come in a range of standard door sizes to help you find a new door that can easily be trimmed to fit your door frame.

The most common door sizes available are:

  • 1981 x 762 x 44mm
  • 1981 x 838 x 44mm
  • 2032 x 813 x 44mm
  • 2082 x 864 x 44mm
  • 2134 x 915 x 44mm

1981mm x 838 x 44mm is generally considered the most common size for external doors, but many door frames will be slightly off this size so the slabs will need trimming or adjusting.

Are Front Doors a Standard Size?

Like all other exterior doors, front doors come in a range of sizes. However, most front doors will be of a similar height – somewhere around 1981mm.

This is not exclusive across all front doors though, so it is still important to carefully measure up if you are looking to replace your front door. You can also be a lot more restricted when it comes to trimming a front door, which makes it even more important to get the right size in the first place.

What Is the Minimum Required Size For An Exterior Door?

External doors are subject to several building regulations including door sizes.

Though they do not necessarily specify the door height or width, the main entrance to your home must have an entrance that is at least 775mm. This is not the width of the door, but the distance between your door jamb and the face of the door when it is opened.

This is an accessibility issue, as any smaller than this will restrict wheelchair access.

What Are Standard Door Widths?

The building regulations surrounding the accessibility of external doors came into force in 2002, so the external door widths vary in older homes.

If your external door frame is slightly narrower than your door width, you can trim the door down but when it comes to unusually large door sizes you are limited. While you can order bespoke doors that are wider, there are restrictions to this based on the weight and other factors of the door.

Another alternative is to pick a set of external French doors or double doors instead. If you are choosing a new front door and are concerned about the security of French doors, you can also pair single doors with one or more sidelights to fill the door width.

How Thick Should an External Door Be?

In order to keep your home secure, external doors should be at least 40mm thick – though the average door thickness of a modern external door is 44mm.

This door thickness will be strong enough to withstand significant impact to keep intruders out. It can also provide a high enough level of insulation to keep your home warm.

Are External Doors Bigger Than Internal Doors?

In general, the dimensions of an internal door and an external door are similar. Particularly in terms of height and width.

The difference lies in external door thickness – interior doors tend to be slightly thicker than exterior ones. The exception is fire doors, as most internal fire doors are around 44mm thick too.

What Is the Size Of A Rough Opening?

A rough opening is the space in a wall that a door frame and door is fitted into (this includes internal doors and external ones). If you are starting from scratch or looking to fully replace a door, you can take the rough opening measurements to work from. Just make sure to allow for the size of the door frame if you are buying an external door slab on its own.

What Does Nominal Door Size Mean?

The nominal door size is the measurement of the door itself. It doesn’t include the door frame. If you are buying a new exterior door based on the nominal door size, don’t forget to leave space to sit around the edge of the door when it is hung.

Can You Trim External Doors?

If you have an external doorway that is not one of the ‘standard’ UK door sizes, you may want to try trimming down an external door to meet your exact specification. This is common with internal doors but with external doors you need to be more careful.

Exterior wooden doors can be trimmed, much like their internal door equivalents. Composite and uPVC doors are not so flexible though. Due to the way these doors are constructed, it is not always possible to alter the door size to fit a smaller door frame.

With most external doors, even if you can change the door size yourself it may not be a good idea. It is important that your external doors create a weatherproof, insulated, and secure seal which can be affected by trimming them down. It can also leave the door vulnerable to absorbing moisture. If you need an external door that is not a standard door size it is usually easier to just order a bespoke or made-to-measure door that will fit without adjustment.

The External Doors Information Centre

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