Reports the tenth dwelling adds to a scheme
The tenth unit adds five weeks, an affordable housing obligation, the full biodiversity metric and a likely committee decision. Price that before the land deal.
Crossing the ten dwelling major threshold reports line changes the application more than any other single unit in a residential scheme. The tenth house adds five weeks to the statutory determination period, brings affordable housing policy into play in most authorities, changes the publicity the council has to carry out, moves the biodiversity calculation from the small sites metric to the full statutory one, and makes a committee decision considerably more likely.
None of that is a reason to build nine. It is a reason to know what the tenth unit costs in evidence and time before the land deal is priced.
What changes when a scheme becomes major
Major development for housing is defined in the Development Management Procedure Order 2015 as 10 or more dwellings, or a site of 0.5 hectares or more where the number of dwellings is not yet known, and separately any development on a site of 1 hectare or more.
The immediate consequences are procedural.
- The statutory determination period becomes 13 weeks rather than eight, and 16 weeks for development subject to environmental impact assessment
- Publicity requirements increase, with major applications advertised in a local newspaper as well as by site notice
- Most authorities have a scheme of delegation that sends major applications to planning committee, or allows members to call them in more easily
- The application fee moves into the major category
- Pre-application engagement becomes worthwhile rather than optional, and some councils offer a planning performance agreement at this scale
Thirteen weeks is the statutory period. In practice an extension of time is common on majors, and agreeing one is normally preferable to a refusal on the eighth week for want of information.
Affordable housing evidence
National policy sets the affordable housing threshold at major development, so ten units is where the obligation usually begins. The proportion and tenure mix come from the adopted local plan, and the requirement is delivered through a section 106 agreement.
An Affordable Housing Statement sets out the proposed provision against policy: the number of units, the tenure split, their distribution across the site, their size mix and how they will be transferred to a registered provider. Where the scheme proposes less than policy requires, the statement has to be supported by viability evidence, which is a different and more expensive document.
Two practical points. Registered providers have their own requirements on unit types, clustering and service charges, and a scheme designed without talking to one can be policy-compliant and unsellable. And in designated rural areas the threshold may already have been lower than ten, so the tenth unit is not always where this starts.
Community involvement expectations
Statutory pre-application consultation does not apply to schemes of this size in England, and a Statement of Community Involvement is not triggered by the thresholds PlanScope uses to flag reports, which sit at 50 units.
Some local plans and supplementary documents do expect community engagement on major applications, and the council's validation list is the place to check. Where engagement is expected, a short statement recording who was consulted, how, what was raised and what changed in response is worth more than a glossy account of a well-attended exhibition.
The publicity change is the bigger practical difference. A newspaper advertisement reaches people a site notice does not, and objections on major schemes typically arrive in greater numbers and later in the process.
Transport evidence at the major threshold
Ten dwellings is a major application but a small one in transport terms. The thresholds PlanScope uses flag a full transport assessment at 50 or more dwellings or 2,500 m2, and national practice guidance expects the scope to be agreed with the highway authority rather than set by a national number.
Expect to provide a transport statement rather than a full assessment: access design and visibility, parking against adopted standards, refuse and emergency vehicle tracking, trip generation, and a short accessibility review covering bus stops, footways and cycle routes. Some authorities ask for a travel plan statement at this scale, particularly where the site is not well served by public transport.
The highway authority's interest rises with major status even when the evidence required does not. Engage early.
Drainage and flood risk consequences
National policy expects major development to incorporate sustainable drainage systems unless there is clear evidence this would be inappropriate, and the lead local flood authority becomes a statutory consultee on surface water drainage for major development.
That changes the Drainage Strategy from a supporting document into a consulted one. Expect scrutiny of discharge rates, attenuation volumes, exceedance flow routing, treatment stages for water quality, and long-term maintenance and adoption arrangements. The maintenance question is the one that stalls approvals: who owns the basin in year 30, and who pays for it.
A flood risk assessment is still driven by zone and site area rather than by unit count, so a major scheme in Flood Zone 1 on 0.7 hectares may not need one, while a nine-unit scheme in Flood Zone 2 does.
The biodiversity change nobody budgets for
This is the change most often missed at ten units.
The small sites biodiversity metric is available only for smaller development, broadly fewer than ten dwellings on a site under one hectare. At ten dwellings the scheme uses the full statutory biodiversity metric instead, which requires more detailed habitat condition assessment, takes longer, and costs more.
The ten per cent gain, the biodiversity gain plan and the 30-year maintenance obligation apply either way. What changes is the rigour of the baseline survey feeding a Biodiversity Net Gain Assessment, and therefore the survey programme. Habitat condition assessment has an optimal season, and a metric run from a winter survey will be challenged.
The statutory metric is expected to be completed by a competent person under the Environment Act 2021 regime, and the biodiversity gain plan must be approved by the local planning authority before development begins.
Deciding whether the tenth unit is worth it
Run the arithmetic honestly.
| Factor | At nine dwellings | At ten dwellings |
|---|---|---|
| Determination period | Eight weeks | 13 weeks |
| Affordable housing | Not usually required | Policy requirement in most authorities |
| Biodiversity metric | Small sites metric | Full statutory metric |
| Publicity | Site notice or neighbour letters | Newspaper advertisement as well |
| Decision route | Usually delegated | Committee more likely |
| Sustainable drainage | Encouraged | Expected, with the lead local flood authority consulted |
The revenue from one more unit has to cover the affordable housing obligation, the additional evidence, the longer programme and the higher risk of a committee refusal. On a scheme of this size that is frequently a losing trade, which is why nine-unit applications are common.
It is not always the wrong call, though. Where the land is already committed, where the site area already puts the scheme into major territory, or where the local plan allocation anticipates a larger number, the tenth unit costs less than the argument about why it is missing.
For the next step up, where the evidence base thickens again, our note on how the report pack changes at twelve units covers what follows. And for a comparison at the other side of the line, reports for a nine-unit scheme on a brownfield site sets out the minor-scheme pack.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required, and the statutory biodiversity metric must be completed by a competent person.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it.
Frequently asked questions
What makes a housing scheme major development?
Ten or more dwellings, or a site of 0.5 hectares or more where the number of dwellings is not yet known, or any development on a site of 1 hectare or more. The site area limbs matter: a nine-unit scheme on 1.1 hectares is major even though the unit count sits below the ten dwelling figure.
Does affordable housing always apply at ten units?
In most authorities, yes, because national policy sets the threshold at major development and the proportion comes from the adopted local plan. In designated rural areas the threshold may already be lower, so ten units is not always where the obligation begins. Check the adopted plan rather than assuming.
Which biodiversity metric applies at ten dwellings?
The full statutory metric. The small sites metric is available only for smaller development, broadly fewer than ten dwellings on a site under one hectare. The full metric needs more detailed habitat condition assessment, takes longer and costs more, and condition assessment has an optimal survey season.
Do I need a full transport assessment at ten units?
Usually not. A transport statement covering access, visibility, parking against adopted standards, vehicle tracking, trip generation and accessibility is normally proportionate. The scope should be agreed with the highway authority, whose interest in the application rises with major status even where the evidence required does not.
How long will a major application take?
The statutory period is 13 weeks, or 16 weeks where environmental impact assessment applies. Extensions of time are common on major applications, and agreeing one is usually better than a refusal for want of information. Committee cycles add further time, since decisions must align with meeting dates.
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.