Part M Accessibility: Level Thresholds, Door Widths & Accessible Bathrooms

Summary

Approved Document M applies to new dwellings and material changes of use (e.g. converting a building to residential use). It does not generally apply to routine work on existing dwellings unless the work is part of an extension or material alteration. However, extensions to existing dwellings do trigger Part M requirements for the new elements.

Part M is often poorly understood by tradespeople. Many builders assume accessibility is something they only need to think about for disabled clients — but Part M requirements apply to ALL new dwellings, regardless of the intended occupants. The regulations are intended to make the UK housing stock usable by the widest possible range of people throughout their lives, including as residents age or face temporary mobility limitations.

The three categories of Part M (Volume 1) for new dwellings are: Category 1 (minimum standard, equivalent to the old "visitable dwelling" standard), Category 2 (accessible and adaptable — requires planning condition to be mandated), and Category 3 (full wheelchair user dwelling — requires planning condition). Most new build housing complies with Category 1 as a minimum; local planning authorities can require higher categories via planning conditions.

Key Facts

• Category 1 minimum doorway width (entrance): 775mm clear width (door leaf ≥ 800mm)
• Category 1 minimum internal doorway width: 750mm clear width (door leaf ≥ 775mm, or 826mm if wall is over 150mm thick)
• Category 2 entrance doorway: 850mm clear width minimum
• Category 2 internal doorways: 750mm minimum clear width; 800mm+ recommended
• Threshold: Level or gently ramped (max 1:20 slope) at main entrance; step threshold not acceptable for Category 1
• Ramp gradient (if level not achievable): Maximum 1:20 for approach ramps; 1:15 for short ramps under 5m
• Handrails to ramps: Required at both sides if ramp exceeds 2m horizontal
• WC on entrance level: Category 1 requires a WC accessible from the entrance level; minimum 900mm × 1,500mm turning space in the WC
• Category 2 WC on entrance level: Must accommodate future adaptation for a shower (wet room conversion possible)
• Corridor width: Category 2 requires 1,050mm minimum in corridors serving the accessible rooms; 1,200mm preferred
• Kitchen: Category 1 requires 1,200mm turning space in the kitchen; Category 2 requires the kitchen to be adaptable
• Stair: Part M staircase requirements (where handrails must be continuous and contrast visually) — see also staircase regs
• Light switches and socket outlets: Category 2 requires switches at 400–1,200mm from floor; sockets at 450–1,200mm — reachable from a wheelchair
• Relevant Part: Approved Document M, Volume 1 (Dwellings), 2015 edition

Quick Reference Table

Detailed Guidance

When Does Part M Apply?

New dwellings (all): Category 1 minimum unless higher category required by planning condition.

Extensions (single dwelling): Part M does not require the extension itself to meet Category 1–3 standards, but any work should not reduce compliance with Part M if the existing dwelling already achieves a standard. Practically:

• New doors added as part of an extension should be 775mm clear width minimum
• Thresholds between new extension and existing dwelling should be level or near-level
• A building notice or plans application for an extension will typically be checked against Part M

Conversions (change of use to residential): Must comply with Part M Volume 2 (Buildings other than dwellings) if the converted units are flats with common areas. The common areas (entrance, corridors, lifts) must meet access standards.

HMOs and shared houses: Complex — falls between Volume 1 and Volume 2; consult Building Control.

Category 1 Requirements in Detail

Category 1 "Visitable Dwellings" is the minimum standard for all new UK housing. The intent is that a visitor using a wheelchair should be able to enter the property and use a WC — even if they cannot access all of the dwelling.

External approach:

• Access from the street/car park to the entrance must be level or gently ramped
• Path minimum 900mm wide; 1,200mm recommended
• If a ramp is needed: maximum gradient 1:20; no single ramp flight over 10m
• Must have level 1,500mm × 1,500mm space outside the entrance door

Entrance door:

• 775mm clear width minimum — measured from the face of the open door to the door stop
• Single leaf door: minimum 800mm door leaf; double leaf: one leaf minimum 800mm
• Level threshold or flush threshold — maximum 15mm step, chamfered 45° if unavoidable
• A level landing minimum 1,500mm × 1,500mm inside the door

Circulation:

• Corridor minimum 900mm wide to the WC and any other room on the entrance level
• Passing places (1,800mm wide × 2,000mm long) every 10m in long corridors

WC on entrance level:

• Must accommodate a 900mm × 1,500mm clear floor space (the space needed for an ambulant disabled person)
• Door outward-opening preferred; inward-opening door must allow 200mm alongside the WC
• Wash hand basin in the WC
• If no WC on entrance level, the entrance floor must have a suitable room that could be converted to a WC in the future

Category 2 — Accessible and Adaptable

Category 2 is a higher standard than Category 1, required when specified in planning conditions (usually for larger housing developments or affordable housing provisions). Key additional requirements:

Wider doorways and corridors:

• Entrance doorway: 850mm clear minimum
• Internal doorways: 800mm clear in principal rooms
• Corridors: 1,050mm minimum width

Entrance level WC adaptable for wet room:

• The entrance level WC must be large enough to be adapted in the future as a wet room/accessible shower room without structural alteration
• Minimum 1,700mm × 900mm clear floor area (1,500mm × 2,100mm preferred)
• Drainage provisions to allow future wet floor installation

Adaptable kitchen and bathroom:

• Kitchen: Space to allow adaptation for wheelchair access (1,500mm turning circle)
• Bathroom: Space for lateral transfer to bath/shower; removable panels under sanitary fittings

Switch and socket heights:

• Light switches: 1,050mm ± 150mm (i.e. 900mm to 1,200mm above FFL)
• Socket outlets: 450mm ± 150mm (300mm to 600mm above FFL) — actually this means the switches at 1,050mm and sockets at 450mm are the target height range
• All outlets should be within the range 400–1,200mm from finished floor level

Stair lift provision (Category 2 two-storey):

• Stair must be designed to accommodate future stair lift installation
• Adequate wall or stringer for bracket fixing; no intrusion at the top and bottom of the stair

Accessible Bathrooms and WCs

The detailed layout of an accessible bathroom depends on the category:

Category 1 WC (minimum):

• 900mm × 1,500mm clear space in front of the WC pan
• Wall-mounted WC at 450–470mm height from floor
• Wash hand basin within the space

Category 2 bathroom/shower room:

• Space for lateral transfer (500mm clear at one side of the WC)
• Reinforced walls at WC and bath/shower for future grab rail installation — typically 100mm thick blockwork or a timber noggin panel within the wall
• The shower or bath must be accessible — walk-in shower or level-access shower area (no step or lip)

Level access shower:

• No step or lip at shower entry
• Drain set low enough for water to clear without ponding — typically a linear drain with 1:60 fall from perimeter to drain
• Non-slip floor tiles (R10 or PTV ≥ 36)
• Fold-down shower seat if Category 3

Frequently Asked Questions

Does Part M apply when I'm just replacing a front door?

No — replacing like-for-like does not trigger Part M. However, if you are installing a new or wider door as part of an extension or alteration, the new door should meet Part M minimums if the work requires a Building Regulations application.

My customer says they don't need an accessible bathroom — they have no disability. Do I still need to comply?

If the property is a new build, yes — Part M Category 1 is a minimum requirement regardless of the occupants' current needs. The regulations recognise that occupants' needs change over time and that property should be usable by visitors with different needs. For extensions to existing dwellings, the requirements are less prescriptive, but good practice suggests building in accessibility features where possible.

What is the minimum size for an accessible WC that can be used as a wet room in the future?

For Category 2, the WC must be large enough to be adapted as a wet room without structural alteration. The minimum is 1,500mm × 2,100mm to accommodate a shower, WC, and wash basin with adequate manoeuvring space. The drain must be in a position suitable for future wet floor use.

Do ramps need a handrail?

For ramps under 2m horizontal length, a handrail on one side is recommended but not mandated by Part M. For ramps over 2m, Part M requires a handrail on both sides. The handrail must be at 900mm above the ramp surface and extend 300mm beyond the top and bottom of the ramp.

Can I use a standard internal door in a new build that must meet Part M?

Only if it meets the clear width requirement. A standard 762mm (2'6") door leaf in a 100mm partition gives a clear opening of approximately 700–720mm — less than the 750mm minimum for Category 1. A 838mm (2'9") door leaf in a 100mm partition gives approximately 780mm clear — meets the standard. For Category 2, use 838mm+ for principal rooms.

Regulations & Standards

• Building Regulations Approved Document M (Access to and use of buildings), Volume 1 (Dwellings), 2015 edition — primary standard for new dwellings

• BS 8300 (Design of buildings and their approaches to meet the needs of disabled people) — more detailed accessible design guidance; AD M references BS 8300

• Equality Act 2010 — broader accessibility obligations for service providers; applies to non-domestic buildings

• Building Regulations Approved Document M — GOV.UK — Official AD M document

• Habinteg — Wheelchair Housing Design Guide — Category 3 wheelchair housing design

• Centre for Excellence in Universal Design — Universal design principles

• staircase regs — Stair handrail requirements and dimensions

• door frames — Door frame and lining sizing for compliant clear widths

• building regs overview — Overview of all Building Regulations parts

• waterproofing — Level-access shower and wet room waterproofing