Counting units where the scheme is an HMO or cluster flats

A scheme of 24 student bedspaces in six cluster flats can be counted as six dwellings, as 24, or as something in between, and the answer decides whether the application is major development. Counting units hmo student cluster schemes correctly matters because the thresholds that follow (affordable housing, biodiversity net gain, transport evidence, community involvement) all key off a number that the application form asks you to supply and that the council is free to dispute.

Get it wrong in your favour and the application is invalidated or renegotiated at committee. Get it wrong against yourself and you have volunteered obligations nobody could have required.

Why the count is contested at all

The statutory definition of major development sits in article 2 of the Town and Country Planning (Development Management Procedure) (England) Order 2015. For residential schemes it is 10 or more dwellings, or a site of 0.5 hectares or more where the number of dwellings is not yet known. The Order says dwellings. It does not say bedrooms, bedspaces, units of accommodation or households.

That works cleanly for houses and self-contained flats. It works badly for a house in multiple occupation, where one planning unit contains several households, and worse for a cluster flat, where the kitchen is shared but each study bedroom has its own shower room and lockable door.

So the question is really one of planning units and self-containment, not arithmetic.

Self-contained flats against bedspaces

A self-contained flat has its own entrance, its own kitchen and its own bathroom, and can be occupied as a single household without using any shared facility. Each one is a dwelling. Ten of them is major development, and all the consequences follow.

Shared living accommodation is different. A seven-bed house in multiple occupation is one planning unit falling into a sui generis use, because Class C4 of the Use Classes Order 1987 covers only small houses in multiple occupation occupied by between three and six residents sharing a basic amenity. A three to six bed arrangement sits in C4. Above six, the use is sui generis and the Order gives you nothing to work from.

For either of those, the conventional count is one dwelling, because there is one planning unit. Councils generally accept that for a conversion of an existing house. They push back when the same logic is applied to a new-build block of 40 bedspaces claiming to be four dwellings.

The practical test officers use is whether the accommodation would release pressure on the general housing market, which is a policy question rather than a definitional one.

Cluster flats and what counts as one dwelling

A cluster flat with eight study bedrooms, a shared kitchen and a shared living space is one flat with eight bedspaces. On a strict reading of self-containment it is a single dwelling, because no occupant has a complete dwelling of their own.

Three features tend to tip an officer towards treating each bedroom as more than a bedroom:

• an en-suite shower room to every study bedroom
• a kitchenette, sink or microwave point inside the bedroom
• separate tenancy agreements with exclusive possession of the room and no shared liability

None of those is decisive on its own. Together they produce accommodation that behaves like a set of tiny self-contained flats, and some authorities assess it that way for policy purposes even while accepting a single planning unit for use class purposes. Say which reading you have adopted and why, rather than leaving the officer to infer it.

Purpose-built student accommodation and the local ratio

Purpose-built student accommodation is normally sui generis. It is not C3, it is rarely C2, and the student exemption people remember from council tax has no planning equivalent.

Where it gets counted is in housing supply. National guidance on assessing housing need accepts that student accommodation contributes to the housing requirement, on the basis of the general market housing it frees up. The conversion is done with a ratio of bedspaces to dwellings drawn from census household data, and the Housing Delivery Test measurement rule book sets out the figure the department applies when it measures delivery.

Local plans often adopt their own ratio, and the adopted figure is the one that binds your application. Look in the housing chapter and in any student accommodation policy or supplementary planning document before you assume the national figure applies. Where the plan is silent, state the ratio you have used and show the arithmetic.

What the count does to affordable housing policy

The practical consequence arrives at the affordable housing threshold. Most plans follow the national position of seeking affordable housing on major development, so the gap between nine and ten dwellings is the gap between no contribution and a full policy-compliant one.

For student schemes the usual answer is a commuted sum calculated from a notional dwelling equivalent, and that is where the ratio does real work. A 150 bedspace scheme at one dwelling per three bedspaces is a 50 dwelling equivalent. At one per five, it is 30. The difference is the whole negotiation.

Set out the calculation in the Affordable Housing Statement rather than burying it in a viability appraisal. The tenure consequences shift as the equivalent figure rises, which is covered in more detail in our note on how affordable housing tenure mix changes with scheme size.

Ecology, transport and consultation thresholds

Four other thresholds move with the count.

Biodiversity net gain is the one that catches people. The small sites route under the Environment Act 2021 regime depends on the development not being major, so a nine dwelling claim that the council re-counts as 24 bedspaces moves the scheme onto the full statutory metric with a competent person preparing it.

Transport is less brittle but more expensive. Student and HMO trip rates per bedspace differ sharply from dwelling rates, so a count that is right for policy may still produce the wrong trip generation. Scope the Transport Assessment against bedspaces and occupancy, not against dwelling equivalents, and say so in the methodology. The same tension appears in how air quality triggers shift as trip numbers grow.

Stating the assumption on the application form

The form asks for the number of residential units proposed and lost. Answer it with the number you can defend, then add a short note in the covering documentation that does four things:

1. Identifies the use class claimed, with the reasoning if it is sui generis
2. Gives the bedspace count, the planning unit count and the dwelling equivalent, each labelled
3. Names the ratio used for the dwelling equivalent and its source in the adopted plan or national guidance
4. Confirms which thresholds have been tested against which figure

That note takes twenty minutes and removes the most common reason these applications stall in validation. An officer who disagrees with your ratio can then say so in week two rather than week eleven.

One honest uncertainty: there is no national rule that settles the cluster flat question, and authorities with large student populations have reached different conclusions on near-identical schemes. Where the count sits on a threshold and the outcome turns on it, a pre-application enquiry that puts the question directly is worth the fee. For a borderline case, our note on EIA screening near the housing threshold covers the same habit of testing the boundary before you submit rather than after.

Enter your postcode on PlanScope to see which reports a scheme of this kind is likely to need once you have settled the unit count.

This is general guidance, not legal advice. Check the position 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.