Part M Building Regulations Explained

What Is Part M?

Part M deals with access to and use of buildings.

For window and door contractors, it is especially important when specifying:

• Entrance doors
• External doors
• Communal entrances
• Commercial doors
• Accessible thresholds
• Door clear openings
• Door controls
• Handles
• Powered doors

The key principle is that buildings should be reasonably accessible and usable by people with a wide range of mobility and accessibility needs.

The Quick Answer

Do not ask:

“What width does a Part M door need to be?”

There isn’t one universal Part M door width.

The correct requirement depends on:

• Dwelling or non-dwelling
• M4(1), M4(2) or M4(3)
• Whether it is the principal entrance
• Direction of approach
• Corridor width
• Whether it is a commercial/public entrance
• Whether the door is powered
• Project planning requirements

The important measurement is often clear opening width, not simply nominal door-leaf width.

Part M Is Split Into Two Volumes

Volume 1 – Dwellings

Covers residential accessibility.

It contains three dwelling categories:

• M4(1) – Category 1: Visitable dwellings
• M4(2) – Category 2: Accessible and adaptable dwellings
• M4(3) – Category 3: Wheelchair user dwellings

M4(1) is the baseline requirement for new dwellings unless the optional M4(2) or M4(3) requirement applies. The government states that M4(2) and M4(3) apply where required by planning permission.

Volume 2 – Buildings Other Than Dwellings

Covers buildings such as:

• Offices
• Schools
• Shops
• Nurseries
• Public buildings
• Commercial premises

The requirements and design guidance are different.

M4(1) – Visitable Dwellings

M4(1) is the normal baseline for new dwellings.

For the principal private entrance, Approved Document M guidance states a minimum clear opening width of 775mm and requires any threshold to be an accessible threshold.

This is an excellent example of why builders should not just order a:

“775mm door.”

The requirement relates to the clear opening, not the leaf width.

What Is Clear Opening Width?

Clear opening width is the usable opening available when the door is open.

It is affected by:

• Door leaf thickness
• Hinges
• Frame
• Stops
• Opening angle
• Reveal geometry

Approved Document M provides specific diagrams showing how the clear opening should be measured.

A nominal 900mm doorset does not automatically mean 900mm clear opening.

Door Leaf Width vs Clear Opening Width

This catches people constantly.

For example, Approved Document M notes that a standard 826mm door leaf up to 44mm thick is deemed to satisfy a 775mm clear-opening requirement in the relevant dwelling guidance.

The leaf therefore needs to be wider than the required usable opening.

M4(2) – Accessible and Adaptable Dwellings

Where M4(2) applies, requirements are more demanding.

For the principal private entrance or appropriate alternative entrance, the guidance includes a minimum clear opening width of 850mm.

Other factors include:

• Level landing
• Door-side nib
• Reveal depth
• Accessible threshold
• Manoeuvring space

So again, specifying only door width is not enough.

M4(3) – Wheelchair User Dwellings

M4(3) has more demanding wheelchair accessibility requirements.

The guidance includes 850mm minimum clear opening widths for relevant doors and significantly greater circulation/manoeuvring provisions.

Do not assume an ordinary Part M entrance-door detail automatically satisfies M4(3).

Accessible Thresholds

The threshold is critical.

A door may provide excellent clear opening width but still create a major wheelchair barrier if the threshold is too high.

For dwellings, Approved Document M repeatedly requires an accessible threshold at relevant principal entrances.

When ordering aluminium, composite or uPVC entrance doors, identify the accessibility requirement before manufacture.

Low Threshold vs Weather Performance

There is often a trade-off between:

• Extremely low threshold
• Weather resistance
• Drainage
• Exposure
• Security

A standard rebated threshold may provide excellent weathering but create an accessibility obstacle.

A low threshold may require careful:

• Drainage design
• Canopy/weather protection
• External levels
• Cill design

The door supplier cannot solve the whole detail without knowing site conditions.

Commercial and Public Entrances

Approved Document M Volume 2 deals with buildings other than dwellings.

The guidance states that principal entrances, main staff entrances and relevant lobbies should be accessible.

For accessible entrances, the threshold should preferably be level.

If a raised threshold is unavoidable, the guidance states a total height of not more than 15mm, with a minimum number of upstands/slopes and upstands above 5mm chamfered or rounded.

Door Opening Force

This matters especially with commercial aluminium entrance doors.

A beautifully designed accessible entrance can still be difficult to use if the closer makes the door extremely heavy.

Approved Document M Volume 2 gives guidance for manually operated entrance doors that the opening force at the leading edge should not exceed:

• 30N from closed to 30° open
• 22.5N from 30° to 60°

under the relevant provision.

This directly affects door-closer specification.

Door Closers

Don’t simply fit the strongest closer possible.

The closer needs to balance:

• Accessibility
• Fire-door requirements where relevant
• Wind pressure
• Door size/weight
• Reliable closing
• Security

This can become technically challenging on large commercial aluminium doors.

Handles and Door Furniture

For manually operated commercial entrance doors, Approved Document M recommends door furniture that can be operated with one hand using a closed fist — for example, a suitable lever handle — and that contrasts visually with the door.

This is much more useful for builders than simply saying:

“Fit a disabled handle.”

Pull-Side Clearance

Commercial accessible entrances also need sufficient space beside the leading edge so wheelchair users can reach and operate the door.

The current Volume 2 guidance identifies an unobstructed space of at least 300mm on the pull side between the leading edge of the door and a return wall for relevant manually operated doors.

This is a building-layout issue, not something the door fabricator can fix after the opening has been built.

Powered Doors

Automatic/powered doors may be particularly useful in:

• Hospitals
• Schools
• Public buildings
• Shops
• High-traffic entrances

Part M guidance addresses matters such as:

• Activation
• Safety sensors
• Opening timing
• Manual controls
• Fail-safe operation

The complete entrance design needs to be considered.

Revolving Doors

A revolving door alone is not treated as an accessible entrance solution in Approved Document M Volume 2.

Where one is used, a suitable accessible entrance door should be available alongside it.

Part M and Part Q

Residential entrance doors may simultaneously need:

• Accessibility under Part M
• Security under Part Q/PAS 24

The threshold, locking and hardware specification therefore need to work together.

Don’t improve accessibility by making an unsupported security modification.

Part M and Part B

Commercial entrance or escape doors can also be affected by fire requirements.

For example:

• Fire door closer strength
• Escape hardware
• Opening force
• Clear width

may all need coordination.

Do not solve accessibility by undermining the fire strategy.

Part M and Drainage

Accessible thresholds work best when external levels and drainage are designed properly.

Typical considerations include:

• Falls away from door
• Linear drainage
• Cill detail
• Canopy
• Exposure
• Waterproofing

The threshold should be considered as part of the building envelope, not merely as an aluminium section.

Common Part M Mistakes

Mistake 1 – Specifying door leaf width instead of clear opening

The usable opening is what matters.

Mistake 2 – Assuming every dwelling needs the same width

M4(1), M4(2) and M4(3) differ.

Mistake 3 – Forgetting planning requirements

M4(2) or M4(3) may be imposed through planning.

Mistake 4 – Using a standard high threshold

Accessibility may be compromised.

Mistake 5 – Ignoring external drainage

Low thresholds need a proper weathering strategy.

Mistake 6 – Fitting an excessively powerful closer

Opening force can become an accessibility problem.

Mistake 7 – Building the return wall too close to the door

Door-side clearance matters.

Mistake 8 – Treating Part M as a door-only issue

The entrance, landing, approach and circulation all interact.

Real-World Example – New House

A builder orders:

900mm composite entrance door

and assumes it complies with Part M.

The actual clear opening is reduced by:

• Frame
• Door thickness
• Hinge position

Whether it complies depends on the actual clear opening and which M4 category applies.

The correct specification is:

“Please provide a doorset giving the required clear opening under M4(1)/M4(2)/M4(3).”

Real-World Example – Nursery

A commercial aluminium entrance door is installed at a nursery.

The closer is set extremely strongly to overcome wind.

The door is now difficult for many users to operate.

Accessibility cannot be judged purely from door width.

Opening force and hardware operation need consideration alongside safety and fire requirements.

Real-World Example – Accessible New Build

Planning requires M4(2).

The architect shows a wide entrance door but the builder has constructed a deep internal reveal and insufficient leading-edge clearance.

The doorset itself cannot fix this.

Accessibility needed coordination between:

• Wall opening
• Door
• Landing
• Threshold
• Internal layout

Builder’s Pre-Order Checklist

Before ordering an entrance door, confirm:

• Dwelling or commercial building?
• Which M4 category applies?
• Required clear opening?
• Door approach direction?
• Required leading-edge clearance?
• Threshold requirement?
• External finished level?
• Internal finished level?
• Drainage?
• Weather exposure?
• PAS 24?
• Fire rating?
• Door closer requirement?
• Powered or manual operation?

Frequently Asked Questions

What does Part M cover?

Access to and use of buildings.

What is the minimum Part M entrance door width?

There is no single universal figure. The required clear opening depends on building type and accessibility category.

What clear opening is required for an M4(1) principal entrance?

The current dwelling guidance gives 775mm minimum clear opening.

What about M4(2)?

The relevant principal private entrance guidance gives 850mm clear opening.

Is M4(2) compulsory on every new home?

No. The government states M4(2) and M4(3) are optional requirements that apply where required by planning permission.

Does a 900mm door mean a 900mm clear opening?

No.

Does the threshold matter?

Yes. Relevant entrances require an accessible threshold.

What is the maximum raised threshold at an accessible commercial entrance?

Where a raised threshold is unavoidable, Volume 2 guidance gives a maximum total height of 15mm under the relevant provision.

Does door closer force matter?

Yes. Volume 2 provides specific opening-force guidance for manually operated entrance doors.

Can Part M and PAS 24 be achieved together?

Yes, with an appropriately designed/tested doorset and threshold configuration.

Related Guides

• Part Q Explained
• PAS 24 Explained
• Part K Explained
• Part B Explained
• New-Build Window Regulations
• Building Control Checklist
• Accessible Thresholds Explained

Trade Tech Technical Support

When requesting an entrance-door quotation, don’t simply write:

“Part M compliant.”

Tell us:

• M4(1), M4(2) or M4(3) where applicable
• Required clear opening
• Building type
• Threshold requirement
• PAS 24 requirement
• Fire requirement
• Opening direction
• Finished floor levels

That lets the doorset be designed correctly before manufacture.

Important: Part M compliance depends on the complete access arrangement, including the approach, landing, door, clear opening, threshold and circulation space. A doorset cannot make an incorrectly designed opening or approach compliant on its own.