Part M Access to Buildings — A UK Trade's Guide to Approved Document M in 2026

What Part M Covers and Where It Applies

Part M of Schedule 1 to the Building Regulations is the requirement; Approved Document M is the official guidance that shows one accepted way of meeting it. It splits into two volumes. Volume 1 deals with dwellings — houses and flats. Volume 2 deals with buildings other than dwellings — shops, offices, workplaces and public buildings. Most domestic trades work to Volume 1, but if you fit out commercial units you will meet Volume 2 as well.

Approved Document M applies in England. Wales has its own version of Approved Document M under the Welsh Building Regulations, broadly similar but maintained separately. Scotland deals with access under Section 4 of its Building Standards Technical Handbooks, which uses different terminology and figures. Northern Ireland covers it under Technical Booklet R. The principles — level entry, usable doorways, an accessible toilet — are common across the UK, but always check the dimensions for the nation you are building in rather than assuming the English numbers apply.

The Three Categories of Dwelling

Volume 1 sets out three optional standards for new dwellings. Which one applies is decided by planning policy and the local authority, not by you — but you need to know which category a job falls into before you price or set out, because the dimensions change.

• Category 1 — visitable dwellings (M4(1)): the baseline standard that applies to almost all new homes unless a higher category is required. A wheelchair user or someone with reduced mobility should be able to visit, reach the entrance and use an entrance-level WC.
• Category 2 — accessible and adaptable dwellings (M4(2)): a higher standard, broadly equivalent to the old Lifetime Homes approach, that makes a home easier to adapt as occupants' needs change. Increasingly required by local plans on new developments.
• Category 3 — wheelchair user dwellings (M4(3)): the most demanding standard, designed so the home is either readily usable by, or easily adaptable for, a wheelchair user throughout.

Category 1 is the default and the one most extension and self-build work is checked against. Categories 2 and 3 only apply where the planning permission or local plan specifically requires them, so read the conditions on the consent before you assume. The rest of this guide focuses mainly on the Category 1 requirements that turn up on routine jobs.

Getting In: Level Approach and Accessible Thresholds

The approach to the principal entrance should be level or gently sloping wherever the site allows. A level approach means a gradient no steeper than 1:20; where the ground falls more sharply, a gentle ramped approach is used instead, kept within the gradients Approved Document M sets out for the length of each section.

The threshold itself is where a lot of finished jobs fail. An accessible threshold should be level, and where an upstand is unavoidable it should be no more than 15mm high and chamfered or pencil-rounded so a wheelchair or buggy can roll over it. This is the figure to drum into anyone fitting external doors: the days of a 50mm or 75mm timber cill step on a new or replacement door in a Part M job are gone. Specify a low-threshold accessible door cill from the outset rather than discovering at sign-off that the step is too high.

Door and Corridor Widths Inside the Home

Part M is about clear opening width, not the nominal door leaf size. The clear opening width is measured between the face of the door when open at 90 degrees and the stop on the frame on the far side — door furniture and the open leaf eat into it. The required clear width depends on the corridor or hallway it opens off and on the direction of approach.

For an entrance door to a Category 1 dwelling, the guidance points to a clear opening of around 775mm. Internal doors to habitable rooms on the entrance level should give a clear opening of at least 750mm where the approach is straight on, rising where the approach is at an angle from a narrower corridor. As a working rule, fitting an 838mm (2'9") or 926mm (3'0") leaf on entrance-level doors gives you the clear width comfortably; a 762mm (2'6") leaf can leave you short once the frame and stop are accounted for. Corridors and passageways on the entrance level should generally be at least 900mm wide, with localised pinch points handled per the document.

The Entrance-Level WC

One of the most commonly forgotten Part M requirements on new dwellings is the WC at entrance level — the downstairs cloakroom toilet. A new house or flat must provide a WC on the entrance storey, positioned and sized so it can be reached and used by a visitor with reduced mobility. The door should open outward (or be arranged so it does not foul a person inside), the basin should not obstruct access to the WC, and there should be clear space in front of the pan.

This catches self-builders and extension clients out regularly. If you are building a new dwelling, an entrance-level WC is not optional decoration — it is a regulatory requirement, and building control will look for it. When fitting one, set the door swing, the basin position and the clear floor space deliberately rather than squeezing the smallest possible cloakroom into a leftover cupboard and hoping it passes.

Switch and Socket Heights

Part M also governs the height of switches, sockets and other controls so that they sit within a reach range usable by most people, including wheelchair users and those who cannot bend easily. For new dwellings the accepted band is to mount wall-mounted switches, sockets, consumer unit controls and similar between 450mm and 1200mm above finished floor level.

In practice that means socket outlets are typically set with their centre around 450mm above the floor rather than the old skirting-level position, and light switches around 1200mm rather than the traditional 1350mm. This is a setting-out detail electricians and first-fix carpenters need to agree before back boxes go in, because moving them after plastering is expensive and obvious. The band applies to new dwellings; it does not force you to lift every socket in an existing house you are merely rewiring, but it does apply to the new work.

Stairs and Steps Where They Apply

Part M is principally about access on the entrance level, so internal stairs between storeys are dealt with more under Part K (protection from falling and impact) than under Part M. However, where steps form part of the approach or are unavoidable within the accessible route, Part M sets expectations for them: suitable going and rise, handrails, and visually contrasting nosings so the edges are easy to see. If your job involves an external step or a change in level on the approach, treat the step geometry and handrails as part of the Part M picture and detail them, rather than leaving a single awkward step that defeats the level-access principle.

Keep the two documents distinct in your head: Part K is about stopping people falling and being hurt; Part M is about whether people can reach and use the building in the first place. A flight of stairs can satisfy Part K and still sit inside a building that meets Part M because the accessible route and WC are provided on the entrance level.

New Builds vs Extensions vs Material Alterations

How hard Part M bites depends on what you are doing. This is the area trades get wrong most often, so it is worth being precise.

• New dwellings: the full Volume 1 requirements apply for the category set by planning — level approach, accessible threshold, usable door and corridor widths, entrance-level WC and reach-range controls all in scope.
• Extensions: the new work must comply, but an extension is not normally required to bring the existing house up to current Part M standard. The key principle is that the building work must not make existing access arrangements worse than before. If the extension changes the entrance or the route to it, you have to maintain at least the access that existed.
• Material alterations: where an alteration affects access — for example reworking an entrance, a hallway or a WC — the altered element must meet the relevant requirement, and again you must not reduce the existing level of access or sanitary provision.

The thread running through all of this is the "no worse than before" principle. You are not always obliged to upgrade an old house to modern standards, but you are never allowed to take away access that was there. Block a level approach with a new step, narrow an existing usable doorway, or remove the only accessible WC, and you have a Part M problem even on a refurbishment.

Non-Domestic Buildings: The High-Level Picture

If you fit out shops, offices or other non-dwellings, Volume 2 of Approved Document M applies and it is more demanding. At a high level the things to plan for are:

• Accessible entrances: the principal entrance should be approachable and usable by wheelchair users, with level or ramped access, suitable door clear widths and powered or easily operable doors where appropriate.
• Ramps and steps: where there is a change in level, ramps are designed to controlled gradients with landings and handrails, and any steps in the accessible route get handrails and contrasting nosings.
• Accessible sanitary facilities: accessible WCs sized and laid out for wheelchair use, with the correct clear transfer space, grab rails and outward-opening doors, provided in the right numbers for the building.
• Internal circulation: corridor widths, lobby sizes and lift provision so that someone can move around the building, not just enter it.

On a non-domestic fit-out, engage with the detail of Volume 2 early — the accessible WC layout in particular is a frequent late-stage failure because the clear transfer space and door swing were never set out properly.

When Part M Is Triggered and How Building Control Fits In

Part M is triggered when work is "building work" under the Building Regulations and that work affects access or use — building a new dwelling, extending, converting a use, or materially altering an access-related element. It is enforced through building control, whether you use the local authority or an approved inspector. The inspector checks your work against the functional requirement, using Approved Document M as the benchmark, and signs off only when the relevant requirements are met.

Planning and building control are separate processes. Planning may set the category of dwelling required (for instance requiring a proportion of Category 2 or Category 3 homes on a site), while building control checks the built dimensions actually deliver it. You can hold planning permission and still fail building control on a Part M point, so read both the planning conditions and the Approved Document before you set out. Part M sits alongside the Equality Act, which places separate duties on service providers and employers about accessibility — but Part M is the built-construction standard your work is inspected against, and that is what this guide is concerned with.

Common Things That Get Picked Up

A handful of issues account for most Part M failures on domestic work. Watch for these before the inspector does:

• Threshold too high: a standard door cill creating a step over 15mm at the principal entrance. Specify a low accessible threshold from the start.
• Doorways too narrow: fitting a leaf that gives less than the required clear opening once the frame, stop and open door are accounted for. Size for clear width, not leaf width.
• No entrance-level WC: a new dwelling completed without the required downstairs toilet, or with one too cramped to use.
• Sockets and switches outside the reach band: back boxes set at the old heights instead of the 450mm–1200mm range on new work.
• Access made worse: an extension or alteration that introduces a step, narrows a route or removes the accessible WC that existed before.
• Approach gradient too steep: a path or driveway approach that exceeds the level or gentle-slope gradients without a compliant ramp.

Quick Reference: Part M Key Requirements (England, Category 1 Dwellings)

Figures are indicative working values for Category 1 dwellings in England. Always confirm the exact requirement in the current Approved Document M for the relevant category and nation before setting out.

Frequently Asked Questions

Does Part M apply to my extension?

The new extension work must comply with Part M, but you are not normally required to upgrade the whole existing house. The crucial rule is that the work must not make the existing access arrangements worse — so if the extension changes the entrance or the route to it, you have to maintain at least the level of access that was there before.

Do I really need a downstairs toilet in a new house?

Yes. A WC at entrance level is a Part M requirement for new dwellings, sized and arranged so a visitor with reduced mobility can reach and use it. It is one of the most commonly missed requirements, so design it in from the start rather than treating the cloakroom as an afterthought.

What is the minimum door width under Part M?

Part M works on clear opening width, not leaf size. Entrance doors point to around 775mm clear and internal entrance-level doors to at least 750mm, increasing where the approach is at an angle. Because the frame, stop and open leaf reduce the opening, fit a generous leaf size to land the clear width comfortably.

How is Part M different from Part K?

Part K is about protection from falling, collision and impact — stair geometry, handrails, guarding and glazing safety. Part M is about access to and use of the building — getting in, moving around and using a WC. They overlap on steps and stairs but answer different questions, and a job often has to satisfy both.

Is Part M the same across the UK?

The principles are similar but the documents and figures differ. Approved Document M applies in England, Wales has its own Approved Document M, Scotland covers access under Section 4 of its Building Standards, and Northern Ireland under Technical Booklet R. Always work to the standard for the nation you are building in.