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

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.

Door width in AD M is a lookup keyed to how the door is approached, not one number. M4(1): principal private entrance 775mm (AD M Vol 1 para 1.14a). M4(2): entrance 850mm (para 2.20d). M4(3): entrance 850mm (para 3.22f), a flat figure with no restricted-approach uplift. For internal doorways, Table 1.1 for M4(1) and Table 2.1 for M4(2) are identical and have four rows pairing the doorway with the hall: 750mm or wider needs a 900mm hall when approached head on; not head on, 750mm needs 1200mm, 775mm needs 1050mm, and 800mm needs 900mm. Para 2.22a adds that every hall or landing in an M4(2) dwelling is at least 900mm. For M4(3), para 3.24d requires every door to be 850mm 'irrespective of the direction of entry', with a hallway of 1050mm (para 3.24a) or 1200mm where the approach to a doorway is not head-on (para 3.24b). Buildings other than dwellings use AD M Vol 2 Table 2: 800mm straight-on, 800mm at right angles to an access route at least 1500mm wide, 825mm at right angles to a route at least 1200mm wide, and 1000mm for external doors to buildings used by the general public. All figures are clear opening widths.

It depends on the category, and gradient is always paired with flight length. M4(1), AD M Vol 1 para 1.7a: individual flights are not more than 10m long at gradients up to 1:15, and not more than 5m long at gradients up to 1:12. M4(2), para 2.10a: 'The gradient is between 1:20 and 1:12', and Diagram 2.1 pairs each gradient with a flight, 1:20 over 10m (500mm rise), 1:15 over 5m (333mm) and 1:12 over 2m (166mm). M4(3), para 3.10a: 'The gradient is between 1:20 and 1:15', so 1:12 is not permitted at all in a wheelchair user dwelling. Buildings other than dwellings, AD M Vol 2 Table 1: 1:20 over 10m, 1:15 over 5m, 1:12 over 2m. Where a flight would exceed its permitted length, break the run with an intermediate landing. Handrails on a dwelling ramp come from AD K 2013, not from AD M: para 2.12c says 'For ramps that are 600mm or less in height: you do not need to provide handrails', and paras 2.12a and 2.12b make handrails on both sides a function of the ramp being 1000mm or wider, not of its rise. In a building other than a dwelling, AD M Vol 2 para 1.26 requires handrails on both sides of a ramped access.

Yes. AD M Vol 1 para 1.17a applies to every M4(1) dwelling: 'A room (which may be a WC/cloakroom or a bathroom) containing a WC is provided on the entrance storey or, where there are no habitable rooms on the entrance storey, on the principal storey or the entrance storey.' For M4(2) and M4(3), an accessible WC at entrance level is required. AD M Vol 1 sets no minimum floor area for a wheelchair accessible WC and the '1500 x 2200mm' figure sometimes quoted appears nowhere in it. Diagram 3.11 gives clear access zones to the WC and basin plus a 1500mm diameter clear turning circle, and Diagram 3.12 example B illustrates a 1650 x 2200mm cloakroom under a note reading 'Dimensions for illustration purposes only'.

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.