M4(2) and M4(3) optional requirements in policy

M4(2) and M4(3) are optional requirements in Part M of the Building Regulations, and they only apply to a dwelling if a planning condition says they do. That is the mechanism worth understanding before anything else: the Building Regulations 2010 provide that an optional requirement has effect only where it is imposed as a condition of planning permission. No condition, no requirement, however firmly the local plan is worded.

So the chain runs local plan policy, then planning condition, then building control enforcement. An architect who finds M4(2) in a policy but not in the conditions on the decision notice is not obliged to build to it, and an authority that forgets the condition has lost the requirement for that scheme.

What the three categories cover

Approved Document M, Volume 1, sets out three categories for dwellings.

M4(1), visitable dwellings, is the mandatory baseline that applies to all new dwellings. It covers approach, entrance and a WC at entrance level, and no condition is needed.

M4(2), accessible and adaptable dwellings, is optional. It requires step-free access to the dwelling, a wider entrance and circulation, a bathroom capable of adaptation, provision for a future stairlift or through-floor lift in a house, and a range of fittings and dimensions aimed at letting the occupier stay in the home as needs change.

M4(3), wheelchair user dwellings, is also optional and has two sub-categories. M4(3)(2)(a) is wheelchair adaptable, where the dwelling is built so it can readily be adapted for a wheelchair user. M4(3)(2)(b) is wheelchair accessible, where it is fully fitted out at completion. Which sub-category applies is a matter for the planning condition, and national guidance indicates that the fully accessible version should only be required where the authority is responsible for allocating or nominating the occupier.

How a policy brings them into effect

The route is a local plan policy, supported by evidence, applied through a condition on each permission.

National guidance on optional technical standards expects an authority that wants to apply M4(2) or M4(3) to set the requirement out in a plan policy, to justify the need, and to have tested the effect on viability at plan-making stage. The policy should state the proportion of dwellings to which each category applies, and for M4(3) it should distinguish adaptable from accessible.

In London the position is set by policy D7 of the London Plan 2021, which requires at least 10 per cent of dwellings to meet M4(3) and all other dwellings to meet M4(2). Outside London the requirement varies, and plenty of plans contain no accessibility policy at all, in which case only M4(1) applies.

One policy development to watch rather than assume. Government has consulted on making M4(2) the mandatory baseline for new homes and has indicated an intention to proceed, with transitional arrangements to be settled. That has not been brought into force, so check the current position on legislation.gov.uk and in the Approved Document before you design to a standard that is not yet required.

The evidence an authority needs

Policies requiring optional standards get tested at examination, and the evidence base is where they succeed or fail.

An authority is expected to show the need, typically through population projections for older households, data on households containing a disabled person, the housing register and any wheelchair user register, and local authority adaptation spending. It is also expected to show that the requirement has been factored into the viability testing for the plan as a whole, and to address whether site-specific circumstances might make compliance impractical.

That last point is the opening for an applicant. Where a site has a gradient that makes step-free approach impossible, or where a conversion of an existing building cannot deliver the approach route M4(2) requires, the policy is normally expressed to allow for site constraints. The argument has to be made with levels and sections, not asserted.

Securing it by condition, and what the condition should say

A condition applying an optional requirement should name the requirement and the units it applies to, and nothing else.

Workable drafting identifies the dwellings by plot number or by reference to an approved schedule, states the category, and references the optional requirement in Schedule 1 to the Building Regulations 2010. Vague drafting, such as a condition requiring dwellings to be "accessible", does not engage the mechanism at all, because the optional requirement has to be imposed as such.

Three practical points follow. The condition has to be on the permission that authorises the dwellings, so on an outline consent the requirement is normally carried through to reserved matters, and on a scheme approved in phases the schedule has to be kept aligned. Building control enforces compliance, not the planning authority, so the architect's information needs to reach the building control body in the right form. And a change to the mix after permission, by a non-material amendment or a section 73 application, should be checked against the condition's schedule, which we discuss in the context of approval of details and discharge of conditions.

What it costs in design terms

The design consequences land in four places, and they are predictable enough to resolve at concept stage.

1. Approach and entrance. Step-free access from the parking space and from the site boundary drives levels strategy, which on a sloping site is the single hardest constraint to retrofit.
2. Vertical circulation in flats. M4(2) compliance in a block normally requires step-free access to dwellings above the entrance storey, which means a passenger lift and changes the economics of small blocks considerably. Check the Approved Document for the detail of when a lift is needed.
3. Internal dimensions. Wider halls and doorsets, clear zones beside beds and sanitaryware, and a bathroom layout capable of adaptation all consume floor area that has to come from somewhere.
4. Wheelchair units. M4(3) layouts need turning and transfer space planned around a 1500 mm circle, a larger bathroom, a parking space capable of being widened to give a clear access zone, and in houses provision for a through-floor lift position.

Plan the M4(3) units first and fit the rest of the scheme around them. Doing it the other way produces wheelchair units in the least convenient locations on the plan, which is both a worse outcome and harder to defend at committee.

An illustrative example

This example is illustrative. A 40-unit scheme in a borough applying a 10 per cent M4(3) requirement needs four wheelchair units. The architect places all four on the ground floor of two blocks, each with level access from a nearby parking space, each with a 1500 mm turning circle demonstrated in the bathroom and the main bedroom, and each with a shower tray at floor level rather than a bath. The remaining 36 units are designed to M4(2), with a lift serving all upper floors in each block. The condition on the permission names the four plots by number and references the optional requirement. Building control checks the detail at plans stage, and the unit schedule in the design statement matches the condition exactly.

Showing compliance at planning stage

An officer is not checking Approved Document M compliance. They are checking that the scheme can deliver what the policy requires, and that the drawings do not contradict it.

What to submit: a unit schedule showing each plot against its category, floor plans for each M4(3) unit type at a scale that shows the clear zones and turning circles, a levels plan or section demonstrating step-free approach where the site slopes, a parking plan identifying the accessible spaces and their relationship to the units, and a short written statement tying it together. The Design and Access Statement is where the access case belongs, and on larger schemes an Equalities Impact Assessment may also be expected given the public sector equality duty under the Equality Act 2010.

Keep the schedule as a live document through to the discharge of conditions, because it is the thing the authority will compare against the as-built position. The full list of report types shows what else a residential scheme of any size usually needs. Enter your postcode on PlanScope to see which reports your site is likely to need.

This is general guidance, not legal advice. Check the adopted policy, the condition wording and the current Approved Document with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.