Question 1

What is the minimum door width for a new-build dwelling?

Accepted Answer

For a new dwelling meeting M4(1) (Visitable dwellings), the minimum effective clear width of the principal entrance door is 775 mm (per AD M Vol 1 2015 Section 2 Table 2). Internal doors should also provide a minimum clear opening width of 775 mm (typically achieved with an 826 mm / 2'9" door leaf). Effective clear width is measured between the door stop on the latch side and the face of the open door. The 850 mm figure often quoted online applies to M4(2) and M4(3), not the default M4(1) standard.

Question 2

What door width is needed for wheelchair access?

Accepted Answer

For M4(2) (Accessible and adaptable dwellings), the principal entrance door requires a minimum 850 mm effective clear width (AD M Vol 1 2015 Table 3). Internal doorways must have a minimum 775 mm clear width with straight-on approach, or 900 mm where there is a side approach. For M4(3) (Wheelchair user dwellings), the principal entrance and all doorways typically need 850 mm clear width for straight approach and 1,000 mm for side approach (Table 4).

Question 3

What is the difference between M4(1), M4(2), and M4(3)?

Accepted Answer

M4(1) Visitable dwellings is the default standard for all new homes — it requires level or ramped access, WC at entry level, and reasonable door widths. M4(2) Accessible and adaptable dwellings has enhanced requirements (wider doors, step-free access, adaptable bathroom, space for future wheelchair turning). M4(3) Wheelchair user dwellings are fully designed for wheelchair use. M4(2) and M4(3) are only required if specified by a planning condition.

Question 4

Do vision panels need to be fitted in doors?

Accepted Answer

AD-M recommends that doors to common corridors in flats should have vision panels to allow people on both sides to see each other. Vision panels should have a zone of visibility between 500 mm and 1,500 mm above floor level. For M4(2) and M4(3) dwellings, glazed panels in doors should also include manifestation at two heights for partially sighted people.

Nominal Door Leaf (mm)	Imperial	Approx. Effective Clear Width
726	2'6"	~670 mm (does NOT meet M4(1))
826	2'9"	~775 mm (meets M4(1) & M4(2) straight)
926	3'0"	~870 mm (meets M4(3) straight)
1,026	3'4"	~970 mm (meets most M4(3) requirements)

Approach Type	Pull Side Clear Space	Push Side Clear Space
Straight on (head-on)	300 mm beside latch	Nil beside latch
Side approach (90°)	300 mm beside latch + 1,200 mm clear	300 mm beside latch + 1,200 mm clear
Threshold level change	Max. 15 mm upstand (bevelled)	Level threshold preferred

Category	When Required	Key Features
M4(1) Visitable	All new dwellings (default)	Level access, entry-level WC, 775 mm clear doors
M4(2) Accessible & adaptable	Planning condition only	Step-free, adaptable bathroom, wider corridors (1,050 mm), wheelchair turning space
M4(3) Wheelchair user	Planning condition only	Full wheelchair dwelling: 1,200 mm corridors, level-access shower, hoist provision

Part M Door Width Requirements

Minimum Effective Clear Door Widths (AD-M)

Common Door Leaf Sizes and Effective Clear Widths

Approach Space Requirements

M4 Category Summary

Scotland & Northern Ireland

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Door Location	M4(1) Visitable (mm)	M4(2) Accessible (mm)	M4(3) Wheelchair (mm)
Principal entrance door	775	850	850
Internal doors (straight approach)	775	775	850
Internal doors (side approach)	775	900	1,000
En-suite / WC door	775	775	850
Existing buildings (reasonable provision)	750	N/A	N/A