UK Toilet Building Regulations Explained: Part G Water Efficiency & Part M Access

Two separate parts of the Building Regulations govern a new toilet in England, and they pull in different directions. Part G limits how much water the dwelling as a whole is allowed to use, which constrains the fittings you choose. Part M governs access and use, which constrains the space around them. A compliant cloakroom has to satisfy both at once, and the second is where most compact schemes come unstuck.

The practical conclusion is that space, not specification, is the binding constraint in most British homes. Water efficient WCs and taps are widely available and easy to specify. Clear floor area in front of the pan, a door that can be operated by someone with limited strength and an approach that a person can actually use are much harder to retrofit into a cupboard under the stairs.

Key findings at a glance

• Approved Document G sets a whole dwelling water efficiency requirement for new homes of 125 litres per person per day, calculated across all fittings rather than measured at the WC alone.
• An optional tighter requirement of 110 litres per person per day applies where a local planning authority has imposed it as a planning condition.
• Because the calculation is a whole dwelling total, a generous shower or bath can be offset by efficient WCs, taps and appliances, and the reverse is equally true.
• The Water Supply (Water Fittings) Regulations limit the flush volume of a single flush WC to 6 litres, which is why dual flush cisterns became standard.
• Approved Document M applies access standards, with M4(1) visitable dwellings as the baseline and M4(2) accessible and adaptable and M4(3) wheelchair user dwellings applying where planning conditions require them.
• Part M is concerned with the space and approach around the WC, including clear floor area and door operation, not with the appearance of the sanitaryware.
• The regulations differ across the UK nations, and Approved Documents G and M apply in England, with separate technical standards in Wales, Scotland and Northern Ireland.

Part G: what the water efficiency rule actually measures

The most common misunderstanding is that Part G sets a limit on the toilet. It does not. Approved Document G sets a consumption figure for the dwelling, expressed as litres per person per day, and compliance is demonstrated by a calculation that adds together the notional consumption of the WCs, taps, showers, baths, dishwasher and washing machine.

That structure gives designers flexibility. A household that wants a deep bath or a high flow shower can still comply by specifying low volume dual flush WCs, lower flow basin taps and efficient white goods. Conversely, an efficient WC does not rescue a scheme built around several generous showers.

The tighter optional requirement matters most in new build developments, because it is applied through planning rather than automatically. Where it applies, the specification of every water using fitting in the home becomes tighter, and the WC choice is one of the simplest places to recover litres.

The flush volume limit is a separate control. Under the water fittings regulations a single flush WC is limited to 6 litres, and dual flush cisterns deliver a full flush and a reduced flush, which is what allows the calculated average consumption to fall. Specifying the cistern is therefore part of the compliance route, not an afterthought, and we point customers to the specification when they browse toilets and bidets UK rather than to the styling alone.

Part M: the space around the fitting

Approved Document M deals with access to and use of buildings. For dwellings it operates in three tiers. M4(1), visitable dwellings, is the baseline standard that applies generally and is concerned with reasonable provision for a visitor with mobility difficulties to approach and enter the home and to reach a WC at entrance level. M4(2), accessible and adaptable dwellings, and M4(3), wheelchair user dwellings, are optional higher standards that apply only where a planning authority has required them.

The consistent theme across all three is circulation. A compliant WC needs clear floor space in front of the pan so a person can approach, turn and sit without obstruction, an unobstructed approach through the door, and door ironmongery that can be operated without tight gripping or twisting. The higher tiers increase the clear space, tighten the approach requirements and introduce provision for adaptation, such as walls capable of taking grab rails later.

In practice this is why so many downstairs cloakrooms in existing houses would not be built the same way today. Squeezing a pan into a space that only works if the user enters sideways satisfies nobody, and where the door opens inward over the pan the arrangement fails on its own terms.

Fitting sizes and the space they need

The table below sets out typical sanitaryware dimensions alongside the clear space we recommend allowing around them. These are standard product dimensions and practical design recommendations. Where a specific regulatory dimension applies to your project, the relevant Approved Document is the authority, not this table.

Fitting	Typical size	Clear space we recommend in front	Practical note
Close coupled WC	Projects around 65cm to 70cm (25.6in to 27.6in) from the wall	At least 70cm (27.6in)	Cistern sits behind the pan and adds to overall depth
Wall hung WC with concealed cistern	Projects around 50cm to 56cm (19.7in to 22in)	At least 70cm (27.6in)	Frame needs a duct or stud wall around 20cm (7.9in) deep
Compact cloakroom basin	Around 35cm to 45cm (13.8in to 17.7in) wide	At least 60cm (23.6in)	Check tap reach so water lands in the bowl, not the rim
Vanity unit with basin	Around 50cm to 60cm (19.7in to 23.6in) wide in small rooms	At least 70cm (27.6in)	Adds storage but increases projection into the room
Inward opening door	Swing arc of the door leaf	Full arc kept clear of the pan and basin	An outward opening or sliding door often resolves a tight plan

Where compact cloakrooms go wrong

Three mistakes recur. The first is the door swing. An inward opening door in a small cloakroom eats the only usable floor area, and it is also a safety problem if someone falls against it from inside. Reversing the swing or fitting a sliding or pocket door usually recovers the space needed.

The second is the basin. A basin that is too small to wash hands in properly, or a tap that discharges onto the rim, makes the room unpleasant regardless of compliance. Where the room will take it, a slightly larger bowl and a taller tap is a better decision than the smallest fitting that will squeeze in, and the compromise is often best solved with a compact unit from our modern bathroom vanities UK selection that combines a usable bowl with storage below.

The third is storage. A cloakroom with no cupboard accumulates cleaning products and spare rolls on the floor, which then reduces the clear space the regulations were protecting. A shallow wall unit above or beside the WC holds what the room needs without projecting into the circulation zone, and slim bathroom storage units UK are designed for exactly that depth constraint.

What this means for UK homes

Treat Part G as a dwelling wide budget rather than a fitting level rule. If the scheme includes a generous bath or shower, recover the water elsewhere with efficient dual flush cisterns, lower flow basin taps and efficient appliances, and get the calculation checked before ordering.

Design the space before choosing the sanitaryware. Establish the clear floor area in front of the pan, the door swing and the approach, then select fittings that fit the plan. A wall hung pan with a concealed cistern buys back depth in a tight room, at the cost of a duct behind it.

Reverse an inward opening door where the plan is tight, and consider a sliding door where there is no room for an outward swing either. Choose lever handles and flush plates that can be used without a firm grip, which costs nothing at specification stage and matters later.

Plan storage deliberately so the floor stays clear, and choose a basin large enough to be usable rather than the smallest that fits. Where the room allows, a slightly wider bowl paired with one of our modern basins UK options improves daily use far more than the extra centimetres cost in circulation.

Methodology

This 2026 report was compiled by the editorial team at Furniture in Fashion from the published requirements of Approved Document G and Approved Document M of the Building Regulations for England, the flush volume limit set by the Water Supply (Water Fittings) Regulations, and our own editorial assessment as a UK furniture retailer supplying bathroom furniture. Fitting dimensions and clearance figures given in the table are standard product specifications and our practical design recommendations rather than regulatory minimums, and readers should refer to the current Approved Documents, or to the equivalent technical standards in Wales, Scotland and Northern Ireland, for compliance. This report includes no proprietary sales data and no survey fieldwork.

Citing this report

Journalists and websites are welcome to cite this explainer with credit to Furniture in Fashion and a link back to our site. It is an editorial summary of how Part G and Part M affect toilet provision in English homes, not legal or building control advice. We are happy to clarify any point for media enquiries.

Frequently asked questions

Does Part G limit how much water my toilet uses?

Not directly. Approved Document G sets a water efficiency requirement for the whole dwelling, expressed as litres per person per day, and the WC is one input into that calculation. The flush volume itself is limited separately, with single flush WCs restricted to 6 litres under the water fittings regulations.

What is the difference between M4(1), M4(2) and M4(3)?

M4(1) covers visitable dwellings and is the baseline access standard. M4(2) covers accessible and adaptable dwellings and M4(3) covers wheelchair user dwellings. The higher two tiers apply only where a local planning authority has made them a condition, and they require more generous space and provision for adaptation.

Do I need building regulations approval to add a downstairs toilet?

Adding a new WC generally engages the Building Regulations because it involves drainage, ventilation and water supply, and the access requirements apply to the provision. Building control approval is the route to confirm compliance, and it is worth establishing before the layout is fixed.

Can the door open inwards in a small cloakroom?

It is common in existing homes, but it is rarely the best arrangement. An inward swing consumes the clear floor area in front of the pan and obstructs access if someone falls against the door. Reversing the swing or using a sliding door usually improves both compliance and daily use.

Do these rules apply across the whole UK?

Approved Documents G and M apply in England. Wales, Scotland and Northern Ireland operate their own building standards with different documents and, in some cases, different requirements, so a project outside England should be checked against the relevant national standards.