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minimum door width uk

Door Width Regulations in England: Part M Minimums Explained

What England's Part M rules say about minimum door widths, how clear opening width is measured, and what it means for a new rear extension.

The Extension Works 1 November 2026
Door Width Regulations in England: Part M Minimums Explained

Door Width Regulations in England: Part M Minimums Explained

Homeowner measuring an open entrance doorway

In England, Approved Document M asks for a clear opening width of at least 775mm on the principal entrance of a visitable (Category 1) home. A standard 826mm door leaf is deemed to meet that. Internal doors have no single fixed minimum: the width you need depends on how people approach the door and how wide the corridor is. Below, we explain what each figure means, how the width is measured, and what it means if you are adding a rear extension.

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TL;DR

  • Principal entrance doors to new homes in England need a 775mm clear opening under Approved Document M Volume 1, and an 826mm leaf is deemed to satisfy it.
  • Clear opening width is the usable gap with the door open, not the size printed on the door leaf.
  • Internal doors link to corridor width: a 750mm opening generally needs a 900mm corridor if you approach head-on.
  • Buildings other than homes follow Volume 2: 800mm for new buildings, 750mm allowed in some existing ones.
  • Planning a rear extension? Settle door and corridor widths at design stage, so you do not widen openings later.

Table of Contents

What Part M actually regulates

Part M of the Building Regulations covers access to and use of buildings. The statutory guidance is Approved Document M, split into two volumes: Volume 1 for dwellings and Volume 2 for buildings other than dwellings. When people search for “door width regulations”, they usually mean one of these volumes, and the first question is which one applies. For a house or flat, it is Volume 1. For a shop, office or community building, it is Volume 2.

Approved Document M is guidance, not a law with one number for every door. It describes ways of meeting the requirements. Building control decides whether your work complies, which is why a figure you read online is only as good as the context it was written for.

The current official text is the 2015 edition incorporating 2016 amendments for dwellings. These rules apply in England. Wales and Scotland have their own guidance, so do not assume an English figure applies there.

Minimum door width in a home: the figures that matter

The principal entrance: 775mm clear

For Category 1 (visitable) dwellings, Approved Document M requires a minimum clear opening width of 775mm for the principal entrance. Category 1 is the baseline for new homes. Higher categories, M4(2) accessible and adaptable and M4(3) wheelchair user dwellings, set stricter standards where a planning condition requires them.

The 826mm leaf shortcut

The same document says a standard 826mm door leaf, up to 44mm thick, is deemed to satisfy the 775mm clear opening requirement in dwellings. Builders often use this as a simple rule of thumb: specify an 826mm leaf and you are covered.

Internal doors: width depends on the approach

There is no blanket “all internal doors must be X mm” rule for homes. Instead, the guidance relates the opening width to the corridor. Approved Document M Volume 1 says that a 750mm opening generally requires a 900mm wide corridor when approached head-on. In a narrow hall where you turn at right angles into a room, the same opening would be harder to use, so a wider door or corridor is needed.

Head-on and turning approaches beside door openings

In practice, this means you cannot judge a door in isolation. The door, the hallway and the turning space work together.

Why 800mm keeps coming up

Many guides quote 800mm as the figure for wheelchair access. It has a basis: the Housing Learning and Improvement Network, discussing the housing standard BS 9266, cautions that effective clear widths under 800mm in entrance doors may stop people with large wheelchairs or limited manoeuvring ability getting through without damage to themselves or the building. So 775mm is the regulatory floor, and 800mm or more is a sensible design target if you want to future-proof a home.

How clear opening width is measured

This is where most mistakes happen. The width printed on a door, or the one you order, is the leaf size. The regulations care about the gap you can actually walk or roll through.

Approved Document M defines the clear opening width as the distance between the inside face of the door when open and the inside edge of the frame or stop. A door leaf that is 826mm wide loses width to the frame, the stop and the thickness of the door sitting in the opening, which is why the guidance has a leaf size and a clear width that differ.

A few practical points follow:

  • Measure with the door open to 90 degrees, from the face of the leaf to the stop on the closing side.
  • Frame depth and stops reduce the gap. A thick frame in a thin wall eats more width than you expect.
  • Hardware can matter. Under the current guidance for dwellings, door furniture can be disregarded in the measurement, but buildings other than dwellings are measured to the first obstruction, including projecting handles.
  • Swapping to offset hinges can gain a little clear width in a tight opening, so ask your joiner about them where a wider frame will not fit.

If you are unsure how your own doorway measures up, ask building control or your design team to check it on the drawings before you order doors.

Standard door sizes versus regulation sizes

Standard sizes are what is on the shelf; regulation sizes are what you must achieve. The most common internal door in England and Wales is 762mm wide by 1981mm high, which is the old 2ft 6in size. It is a very common choice for bedrooms and bathrooms. But a 762mm leaf gives a clear opening noticeably narrower than 762mm once it is hung, so it does not automatically meet the 775mm figure used for entrances.

That is not a problem for most internal doors in an ordinary home, where the guidance links width to the approach route. It does mean you should not assume “standard” equals “compliant” for an entrance or any door you want to be accessible.

Door Typical size or figure Source of the number
Principal entrance, new home (Category 1) 775mm clear opening Approved Document M Vol 1
Leaf deemed to satisfy 775mm 826mm leaf, up to 44mm thick Approved Document M Vol 1
Internal door, head-on approach 750mm opening with 900mm corridor Approved Document M Vol 1
Most common internal leaf 762mm Door industry sizing
Non-domestic, new building, straight-on approach 800mm effective clear width Approved Document M Vol 2
Non-domestic, existing building, straight-on approach 750mm effective clear width Approved Document M Vol 2

Can a door be 700mm wide?

It depends on the door and the building. A 700mm opening is below the figures above for entrances and for most accessible routes, so it would not satisfy them. There is one useful official clarification, though. The Approved Document M FAQ says that for double doors to a rear garden of an individual dwelling, which are not the principal or an alternative entrance, a head-on approach can reasonably provide at least 750mm clear opening in one or both leaves. Smaller leaves may be reasonable where both operate together and building control is satisfied.

This matters for rear extensions, because patio and bifold doors are the most common new openings. If you are fitting a set of doors to the garden, the figure to check is the clear opening with the doors open, and your building control officer has the final say.

Open bifold doors create a clear garden opening

Doors in buildings other than homes

If the question is about a shop, workplace or other non-domestic building, Volume 2 applies. For new buildings, Approved Document M Volume 2 specifies an effective clear width of 800mm for straight-on approaches. In existing buildings, the same document allows a reduced effective clear width of 750mm for straight-on approaches.

Volume 2 also covers how hard a door is to open. For manually operated, non-powered entrance doors, the opening force must not exceed 30N from 0 to 30 degrees open and 22.5N from 30 to 60 degrees. Door furniture should be operable with one hand using a closed fist. These force limits are written for non-domestic buildings, so they are not a test your front door at home has to pass.

What this means for a rear extension

A single-storey rear extension usually adds three kinds of doorway: an opening between the existing house and the new space, doors to the garden, and sometimes a new internal door to a utility or WC. Each has different considerations.

  1. The opening into the extension. This is often a widened or newly formed opening in an existing wall, and it usually carries a structural beam. Its width is a design choice, so it is easy to make generous early on. It is costly to enlarge after the build.
  2. Garden doors. Sliding, bifold or French doors give wide openings by nature, but check the clear width with the doors in their open position, as the FAQ above implies.
  3. Internal doors and corridors. If the extension includes a ground-floor WC or shower room, plan the approach route and door swing together.

Because a new opening in an existing house can change how the whole ground floor flows, it pays to think about who will use the space in ten years, not just today. Our guide to accessible extension design that avoids retrofit covers how we use 3D design to test widths and turning space before anything is built.

When you work out how far your extension can go, door positions also depend on the footprint. Our overview of how big a rear extension can be under permitted development is a good companion to this one.

A short checklist before you order doors

  • Identify which Approved Document applies: Volume 1 for a home, Volume 2 for anything else.
  • Ask whether the door is a principal entrance, an internal door or a garden door, because the guidance treats them differently.
  • Work out the approach: head-on or from the side, and how wide the corridor is.
  • Measure clear opening width with the door open, not the leaf size on the order form.
  • Check whether any planning condition requires M4(2) or M4(3) standards, which are stricter than the Category 1 baseline.
  • Confirm the plan with building control before the doors are ordered, since they have the last word.

Perspective

We design a lot of rear extensions, and doors are where small decisions turn into big regrets. A homeowner picks a standard leaf, the frame goes in, and only then does anyone check the clear opening or how the hallway approaches it.

That is why we put door and corridor widths into the 3D model from the start. When you can see the opening in your own house, with the door swung back, it is obvious whether the route works. Nobody has to interpret a table of millimetres.

Our approach is to keep design, planning, structural calculations and construction in one in-house team, so the person drawing the opening is the person who knows what the builder will fit. We treat clear opening width as a design target, not an afterthought, and we agree the details with building control as part of the service.

The result we are aiming for is a fixed, VAT-inclusive price that already reflects the doors you chose, with no surprise variations because an opening turned out too narrow.

Esskay

Plan your extension with the doors right first time

If you are considering a single-storey rear extension in Sutton, Morden or the surrounding areas we cover, you can see your layout, door positions included, in a live 3D model and get an instant fixed price. Our design, planning, structural calculations and build are handled by one in-house team, and the work carries a 12-month workmanship warranty.

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FAQ

What is the minimum door width in the UK?

There is no single UK-wide minimum for every door. In England, the principal entrance of a Category 1 dwelling needs a 775mm clear opening. Internal doors depend on the approach and corridor width, and non-domestic buildings follow Volume 2, with 800mm for new buildings.

Is a 762mm door wide enough?

It is the most common internal size, but its clear opening once hung is narrower than the leaf. For an entrance, the guidance deems an 826mm leaf to give 775mm clear, so a 762mm leaf would not be the safe choice there. For internal doors, check the opening against the corridor width the guidance links it to.

Does the clear opening width include the door handle?

In dwellings, Volume 1 allows door furniture to be disregarded when measuring. In buildings other than dwellings, effective clear width is measured to obstructions on the hinge side, which includes projecting furniture. Check which volume applies before you measure.

Can I fit 700mm doors in a new extension?

A 700mm opening is narrower than the main figures in the guidance. The official FAQ allows for rear garden double doors, which are not the principal entrance, to give at least 750mm clear in one or both leaves on a head-on approach. Always confirm with building control first.

What are the door opening force limits?

For manually operated, non-powered entrance doors in buildings other than dwellings, the force must not exceed 30N from 0 to 30 degrees and 22.5N from 30 to 60 degrees. These limits are in Volume 2, so they are not a requirement for a home’s front door.

Sources