Water efficiency and optional technical standards by scale
The 110 litre water standard and the accessibility requirements apply only where local policy adopts them, by condition. Here is what each demands in design terms.
The optional water efficiency standard of 110 litres per person per day, the accessible and adaptable dwelling requirement and the wheelchair user dwelling requirement all share one feature: they apply only where the local plan has adopted them, supported by evidence, and they are then imposed by planning condition and enforced through the building regulations. There is no national default. Two neighbouring authorities can require entirely different things of the same house type.
The second feature is that, unlike affordable housing or a transport assessment, these standards do not switch on at a scheme size. Where the policy exists, it applies to a single dwelling as much as to 500, which catches small developers who assume that small means exempt.
How an optional standard becomes a requirement
The optional standards were created so that councils could go beyond the building regulations baseline where local circumstances justified it, rather than through locally invented technical requirements.
The route is consistent. The authority adopts a local plan policy, supported by evidence in the plan's examination, and then imposes the standard on individual permissions by condition. The condition refers to the optional requirement in the building regulations, and building control checks compliance at plans and completion stage.
That has a practical consequence worth holding onto. The planning condition is what creates the obligation, so check the decision notice rather than assuming the baseline applies. And because building control enforces it, a design that satisfies the planning officer but not the approved inspector is still a problem.
The tighter water efficiency standard
The baseline requirement for new dwellings is a whole building water consumption calculation, and the optional requirement tightens the figure to 110 litres per person per day.
The design response is a fittings schedule rather than a technology. Lower flow rate taps and showers, dual flush cisterns with a lower effective flush volume, smaller baths, and a dishwasher and washing machine specification within stated consumption figures. The calculation is done using the method set out in the building regulations guidance, and it is straightforward once the fittings are chosen.
Two design traps. A large bath can consume enough of the allowance to force the shower flow rate below what an occupier will accept, and the calculation has to be done before the sanitaryware is specified rather than after. And rainwater or greywater reuse can contribute, but the credit given is specific and modest, so it is rarely the answer to a failing calculation.
Water stressed areas are where the policy is most common, and the evidence base for the policy usually refers to the water resources position in the region. Where the policy applies, a Sustainability Statement is the natural place to record the calculation and the fittings schedule.
Accessible and adaptable dwellings
The accessibility requirements form three levels. The baseline applies to all new dwellings and concerns visitable dwellings. The optional accessible and adaptable standard adds step free access to the dwelling, a wider entrance and circulation, a ground floor toilet, structural provision for a future stairlift or through floor lift, and bathroom walls capable of taking grab rails.
The design consequences show up early: level thresholds and the external approach gradient, the width of the entrance door, the size of the hall and the position of the stair, and the ground floor plan making room for a cloakroom that meets the requirement.
On a sloping site the external approach is the hard part. A step free route with an acceptable gradient from the parking space to the entrance can drive the whole site levels strategy, so test it at layout stage rather than at building regulations stage.
Wheelchair user dwellings and the proportion question
The wheelchair user requirement has two forms: wheelchair adaptable and wheelchair accessible. The stricter of the two is normally applied only where the authority is responsible for allocating or nominating the occupant, because designing a dwelling for a specific wheelchair user who has not been identified is not possible.
Policies usually express the requirement as a percentage of the units on a scheme. That is where scale really does bite, because a percentage applied to a small scheme produces a fraction of a dwelling and the policy has to say how it rounds.
| Scheme size | Practical effect of a ten per cent policy |
|---|---|
| 1 to 4 units | Usually nil after rounding, but check the policy wording |
| 5 to 14 units | One unit, and the layout has to accommodate it |
| 15 to 24 units | Two units, usually best placed on the ground floor |
| 25 units or more | A schedule agreed with the authority, sometimes by tenure |
Get the rounding rule and the tenure split confirmed in writing before the layout is fixed. A wheelchair user dwelling added after the plan is drawn usually costs another unit.
The evidence base a local policy needs
A policy imposing an optional standard has to be justified at examination, with evidence of need and consideration of viability and the effect on housing delivery. That matters to applicants in two situations.
Where the plan is old and the policy predates the current standards, check whether it actually adopts the optional requirement or simply expresses an aspiration, because an aspiration is not a basis for a condition.
Where the policy is in an emerging plan, weight is a matter of judgement, and a condition imposing a standard from a policy that has not been examined is open to challenge.
Where an applicant argues that the standard cannot viably be delivered on a particular site, that is a site specific viability argument rather than an attack on the policy, and the evidence has to be specific.
Securing them on small sites
On a single plot the practical position is simple. Read the decision notice, identify which optional requirements the conditions impose, and give the schedule to the building control body at the outset.
Three steps avoid the common failure.
- Get the water calculation done at the time the sanitaryware is specified, and keep the fittings schedule with the approved drawings.
- Confirm the external approach gradient and the parking to entrance route on the levels drawing, before groundworks.
- Ask the building control body to confirm which optional requirements it is assessing against, because it works from the conditions and may not have seen the planning correspondence.
Designing to the standards from the outset costs very little. Retrofitting them after the foundations are set costs a great deal, and the standards that look like paperwork at planning stage are the ones that reappear as a completion problem.
Energy and carbon requirements follow a similar pattern of scaling with scheme size and local policy, which we cover in energy and carbon evidence as a residential scheme scales, and the mix and space standard questions are set out in housing mix and space standards as schemes grow. Where a policy requires a formal energy submission, an Energy Statement carries that work.
One honest uncertainty. Government has signalled an intention to raise the accessibility baseline for new homes, and the implementing changes and transitional arrangements are the thing to check rather than to assume, so confirm the current position in the building regulations and in the council's policy before fixing a house type range.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. This is general guidance rather than legal advice, so confirm which optional standards apply with your local planning authority and your building control body.
Frequently asked questions
Does the 110 litre water standard apply everywhere?
No. It is an optional requirement that applies only where the local plan has adopted a policy requiring it, supported by evidence, and where the planning permission imposes it by condition. Check the decision notice rather than assuming, and note that building control enforces it once the condition is in place.
How is the tighter water standard achieved?
Through a fittings schedule rather than a technology: lower flow taps and showers, dual flush cisterns with a lower effective volume, a smaller bath, and appliances within stated consumption figures. Do the whole building calculation before the sanitaryware is specified, because a large bath can force the shower flow rate below what occupiers accept.
What does the accessible and adaptable standard require?
Step free access to the dwelling, wider entrance and circulation, a ground floor toilet, structural provision for a future lift, and bathroom walls capable of taking grab rails. On a sloping site the external approach gradient from the parking space to the entrance is the hardest element and should be tested at layout stage.
How many wheelchair user dwellings will be required?
Policies usually set a percentage, so the answer depends on scheme size and on the policy's rounding rule. The stricter wheelchair accessible form is normally applied only where the authority allocates or nominates the occupant. Confirm the rounding and any tenure split in writing before the layout is fixed.
Do these standards apply to a single house?
Yes, where the local policy applies, because optional technical standards do not switch on at a scheme size in the way affordable housing thresholds do. The exception is a percentage based wheelchair requirement, which may round to nil on a very small scheme depending on how the policy is worded.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.