Approved Document M in plain English
Part M covers access to and use of buildings. It is the accessibility part: ramps, door widths, WC provision, approach routes and level thresholds. The first thing to establish is which of its two volumes applies to your job, because they give different answers.
Volume 1 or Volume 2: get this right first
Approved Document M is published as two separate volumes.
- Volume 1, Dwellings. Houses and flats.
- Volume 2, Buildings other than dwellings. Everything else, from a shop to a school to an office.
They differ on ramp gradients, ramp widths, handrails and much else. A great deal of the UK guidance online quotes Volume 2 without naming it, which means a builder putting a ramp at a domestic front door reads a requirement for a 1500mm wide ramp with handrails on both sides when Volume 1 asks for 900mm and no handrail.
The three optional standards for new dwellings
Volume 1 contains three standards, and only the first applies automatically.
| Standard | What it is | When it applies |
|---|---|---|
| M4(1) | Visitable dwellings | The baseline. Applies to new dwellings. |
| M4(2) | Accessible and adaptable dwellings | Only where a planning condition imposes it. |
| M4(3) | Wheelchair user dwellings | Only where a planning condition imposes it. |
M4(2) and M4(3) are not a menu you pick from and not a standard that applies because a scheme sounds accessible. They arrive through planning. Read the decision notice, because discovering an M4(2) condition after the slab is down is an expensive way to find out.
Ramps
Volume 2 allows 1:20 for a flight up to 10 metres, 1:15 up to 5 metres and 1:12 up to 2 metres, with a maximum rise of 500mm per flight, a minimum surface width of 1500mm and handrails on both sides. Volume 1 allows 1:15 up to 10 metres and 1:12 up to 5 metres, with a minimum width of 900mm and no handrail requirement.
Work a ramp out against the right volume with the calculator, which asks which building it is before it answers.
Door clear widths
Clear width is measured through the open doorway, not the size of the door leaf, and it depends on which way you approach. A straight approach needs less room than one where someone has to turn into the opening.
| Direction and approach | New buildings | Existing buildings |
|---|---|---|
| Straight on, without a turn | 800mm | 750mm |
| At right angles, corridor at least 1500mm wide | 800mm | 750mm |
| At right angles, corridor at least 1200mm wide | 825mm | 775mm |
| External doors to buildings used by the general public | 1000mm | 775mm |
These figures are from Volume 2. A standard 838mm door leaf does not give an 838mm clear width, because the frame, the stop and the open leaf all eat into it. Measure the clear opening.
Why Part M is worth reading even on a small job
Part M is the cheapest part of the regulations to get right at design stage and one of the most expensive to fix afterwards. A door 50mm too narrow, a threshold 20mm too high or a ramp at the wrong gradient are all trivial on a drawing and all involve taking something out once it is built. It also tends to be the part an inspector checks carefully, because it is easy to verify with a tape.
Catch it at design stage, not at inspection
Built Simple keeps the drawings, the specs and the programme on one job so the decision made at design is the one that reaches site. Free to start.
Frequently Asked Questions
What is Part M of the building regulations? Part M covers access to and use of buildings. It deals with approach routes, level thresholds, ramps, door widths, WC provision and circulation space. It is published in two volumes, one for dwellings and one for other buildings.
What is the difference between M4(1), M4(2) and M4(3)? M4(1) Visitable dwellings is the baseline standard for new dwellings. M4(2) Accessible and adaptable dwellings and M4(3) Wheelchair user dwellings are optional higher standards that apply only when a planning condition imposes them.
What is the minimum door width under Part M? 800mm clear width for a straight on approach in a new building, rising to 825mm where the approach is at right angles from a 1200mm corridor, and 1000mm for external doors to buildings the public uses. Clear width is the opening, not the door leaf size.
Does Part M apply to my house extension? Part M applies to building work generally, but the requirements for an extension are not the same as for a new dwelling. Volume 1 is the relevant volume, and your building control body will confirm what applies to the specific work.
Which volume of Approved Document M applies to a house? Volume 1, Dwellings. Volume 2 covers buildings other than dwellings. Most ramp guidance published online quotes Volume 2 without saying so, which gives the wrong answer for domestic work.
Related calculators and guides
Sources
- Approved Document M, Volume 1, Dwellings, 2015 edition incorporating 2016 amendments, HM Government.
- Approved Document M, Volume 2, Buildings other than dwellings, 2015 edition incorporating 2020 and 2024 amendments, HM Government.
- Building Regulations 2010, Schedule 1, Part M. Approved Documents are free under the Open Government Licence.
