What are the Part M categories?

Part M has three categories: M4(1) Visitable dwellings (minimum standard for all new homes), M4(2) Accessible and adaptable dwellings (wider doors, level access, adaptable bathroom), and M4(3) Wheelchair user dwellings (designed for wheelchair users from the outset). M4(2) and M4(3) are applied through planning conditions.

What door widths does Part M require?

M4(1): entrance door 775mm clear, internal 750mm. M4(2): entrance 850mm, internal 775mm. M4(3): entrance 900mm, internal 850mm. These are clear opening widths measured between the door face and the frame when the door is open 90 degrees.

What is the maximum ramp gradient?

The maximum ramp gradient is 1:12 (8.3%) for ramps up to 2m long. For ramps 2-5m: maximum 1:12. For 5-10m: 1:15 recommended. Ramps over 10m need intermediate landings (minimum 1.2m long). Handrails are required on both sides for ramps steeper than 1:15 or longer than 2m.

Do all new homes need a ground floor WC?

Under M4(1), a WC should be provided at entrance level or the entrance storey. For M4(2) and M4(3), an accessible WC at entrance level is mandatory. The WC should be large enough for wheelchair access in M4(3) — minimum 1500x2200mm clear floor space.

What is a level threshold?

A level threshold has a maximum step height of 15mm. The entrance should be accessible without steps, or with a ramp as an alternative. Weather protection (canopy) and drainage at the threshold help manage water ingress. Recessed matwell inside the door helps with water and dirt management.

TradeCalculator

Part M Access Calculator — Door Widths, Ramps & WC Provision

Check Part M accessibility requirements for entrance thresholds, door widths, corridor widths, ramp gradients and ground floor WC provision.

Building type / category

Entrance door clear width

Internal door clear width

Corridor / hallway width

Threshold height

Level entrance available

How We Calculate This

This calculator checks key accessibility dimensions against Part M requirements for the selected category.

Checks performed

Entrance and internal door widths
Corridor and hallway widths
Entrance threshold height
Ramp gradient and length
Ground floor WC provision

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.