Technical Study: Part M Bathroom Layouts

Building Regulation Part M: Access to and use of Buildings – Dwellings, deals with many aspects of access and use of buildings, including the design of ramps, doorways, entrances and corridors. A key part of this document is the layout of bathrooms so each sanitaryware item has the right access for use as well as bathrooms having the space to be adapted in the future to make them more accessible.


[To Download a FREE PDF of this guide scroll to the end]

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Accessible design is good design…

This month we have created a package of helpful CAD blocks of sanitaryware and symbols to help when planning out bathroom layouts so that they comply with Part M.

Part M Bathroom Layouts

All our members also have access to the full set of 30 Part M Bathroom layouts and sanitaryware symbols as CAD blocks so you can simply drag and drop into your projects.

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Building Regulations Part M: Access to and use of buildings, Volume 1: Dwellings


2015 edition incorporating 2016 amendments – for use in England


Within this document there are three sections M4(1), M4(2) and M4(3). Part M4 has evolved from Lifetime Homes guidance which was designed to help design spaces for future adaptation as users get older and to allow all users to benefit from easy access. Most of the information below does not apply to works such as extensions or buildings of architectural interest such as Listed Buildings. However, where possible it is always advised to use these key dimensions to make spaces as inclusive and adaptable for the future. Some councils and building control officers may require some of these features to be met if possible even if not required.

M4(1) Category 1: Visitable dwellings

01 SL15  Part M4(1) WC

This is defined as allowing reasonable provision for people to gain access and use the dwelling and its facilities.

Requirement M4(1) does not apply to an extension, to a dwelling or any part of a building that is used solely to enable the building or any service or fitting in the building to be inspected, repaired or maintained.

 Whilst extensions are not covered by Part M, some council’s may set this as a requirement for large extensions and refurbishments or where they can be met.

Bathroom Key Points Part M4(1)

02 SL11 WC
  • A WC/cloakroom or bathroom should be provided on the entrance storey or, where there are no habitable rooms on the entrance storey, on the principal storey.
  • There should be 750mm of space in front of the toilet to allow for suitable access.
  • When accessed head on the toilet should have 450mm to either side although 500mm is preferred.
  • With oblique access to the toilet, the side opposite the access can be reduced to 400mm.
  • Basins should be positioned to avoid impeding access although a maximum encroachment of 200mm is usually acceptable.

M4(2) Category 2: Accessible and Adaptable dwellings

03 SL19 Part M4(2) Bathroom
04 SL21 Part M4(2) WC

M4(2) optional requirement is defined as allowing for reasonable provision must be made for people to gain access to and use the dwelling and its facilities.

This requirement will usually be flagged at the planning stage. It will usually apply to all new dwellings.

The provision is designed to meet users of different needs including some older or disabled people and to allow adaptation of the dwelling to meet the changing needs of occupants over time.

Bathroom Key Points Part M4(2)

05 SL06 Bath
06 DL07 Shower M4(2)
  • A dwelling must have a room within the entrance storey that provides a WC and basin (which may be within a WC/cloakroom or a bathroom).
  • If you do not have a primary bathroom on the entrance floor of a dwelling, a WC/cloakroom must be provided which can be adapted in the future to allow for a potential level access shower.
  • A bathroom must be located on the same storey as the primary bedroom. If this is on the entrance storey, a WC does not need to be provided.
  • The WC or bathroom should provide a level access shower or a potential level access shower as shown in the diagrams below.
  • All walls, ducts and boxings to the WC/cloakroom, bathroom and shower room should be strong enough to support grab rails, seats and other adaptations that could impose a load of up to 1.5kN/m2.
  • Further to the access zones in Part M4(1), hand basins will need an access in front of 1100mm with a maximum overlap of 300mm into the basin as far as any fixed obstruction, such as a vanity unit, pedestal or trap allow.
  • Baths will require 1100mm x 700mm adjacent space for access.
  • Access areas can usually overlap.
  • The future level shower will require 1000mm x 500mm access to one side.
  • The 1500mm diameter turning circle of a wheelchair must not be obstructed by sanitaryware although it can overlap the level shower.
  • Stack and drainage positions to be clear of access zones.
  • Any radiators or towel rails should be clear of all access zones.

M4(3) Category 3: Wheelchair user dwellings

07 SL25 Part M4(3) Bathroom

M4(3) is defined as allowing reasonable provision to be made for people to gain access to and use the dwelling and its facilities.

The provision made must be sufficient to meet the needs of occupant who use wheelchairs either from the outset or to allow simple adaptation of the dwelling to meet their needs.

This section sets out the provisions for both wheelchair adaptable or wheelchair accessible bathrooms. Those which are adaptable follow similar rules to Part M4(2). We will therefore be focusing on wheelchair accessible bathrooms in this section. Usually this requirement will only be required if building more than 10 units, then a certain percentage of the units may need to be fully wheelchair adaptable. A client may also specifically request a wheelchair accessible unit.

Different provisions for bathrooms and WCs are required depending on the bedroom numbers, size and storeys of the dwelling. These are referenced in Table 3.5 of the Building Regulations.

Bathroom Key Points Part M4(3)

05 SL06 Bath
  • Every dwelling should have, on the entrance storey, a wet room (which may be a WC/cloakroom or a bathroom) that contains a WC, a basin and an installed level access shower.
  • Further to the access areas mentioned in the previous sections, a level shower is required with a minimum 1200mm x 1200mm in a bathroom or 1000mm x 1000mm if a WC should be provided. 
  • A zone of 500mm depth around the shower is required, with 500mm encroachment allowed on the wall side for sanitary fittings. 
  • A wheelchair 1500mm diameter can only encroach the level shower by 500mm. 
  • A 1000mm long x 1000mm high x 100mm wide zone on the wall side of the toilet should be kept for fitting of grab rails.
  • The hand basin activity zone depends on whether it is in a bathroom or WC. Some may require no installations under, other than essential traps and drainage connections allowing the approach by a wheelchair user.


Approved Document Part M provides a range of different requirements depending on the M4 category, which can be a little overwhelming at times.

Download our guide as a handy PDF so you have the main key points at your fingertips when you design your next project.

Download the Guide

12 Part M Bathroom Layouts

Get the Drawings

The Detail Library includes a complete set of sanitary CAD blocks along with standard layouts for WC, En-suite and Bathrooms that are compliant with Approved Document Part M. All members can find the Doc M Bathroom Layout Pack here.

Part M Bathroom Layouts and Sanitaryware CAD Blocks

For More Inspiration…

For More Inspiration…


While Approved Document Part M provides minimum requirements for accessibility, it is worth exploring the topic further by consulting the websites and documents mentioned in our resources section below.


Building Regulations Approved Document Part M –

Book: Wheelchair Housing Design Guide by RIBA Publishing and Habinteg

Homes for Life Guide to Accessible Homes –

NDA Building For Everyone –


Written by Aida Rodriguez-Vega, architect and researcher. At the Detail Library, Aida keeps busy by carrying out technical research and drawing new details for the ever-growing library.