Splitting a site to stay below ten units

Splitting a housing site into two applications of nine dwellings to stay under the major development threshold does not usually work, because the authority looks at the planning unit and the relationship between the proposals rather than at the red line on each form. Common ownership, a shared access, overlapping timing and interdependent infrastructure are the tests that get applied, and they are applied on the facts. An applicant who draws two red lines and says nothing about the other half is taking a risk with the permission itself rather than only with validation.

There are occasions where two separate applications are entirely proper. The difference between those and an avoidance exercise is usually visible from the drawings.

Why the temptation exists

At ten dwellings a scheme becomes major development. The determination period moves from eight weeks to 13, newspaper publicity is required, the lead local flood authority becomes a statutory consultee on drainage, national affordable housing policy applies, and the full statutory biodiversity metric replaces the small sites metric.

On a marginal site the cost of crossing that line can exceed the value of the extra homes, as the arithmetic in obligations and the levy at different scheme sizes shows. So the idea of two nine unit applications has obvious appeal.

The thresholds exist to put larger schemes through more scrutiny and to capture contributions from them. Splitting a site to avoid that is what officers call salami slicing, and most development management teams have seen it many times.

How authorities identify a single planning unit

The planning unit is a long established concept used to decide what the relevant area of land is for assessing a change of use or a development. The courts have treated the unit of occupation as the starting point, subject to whether physically separate areas are in distinct and separate uses.

Applied to a split housing site, officers look at the land as a whole and ask whether the two proposals are in substance one development. The questions are practical.

• Is the land in the same ownership or under the control of the same party or connected parties?
• Do the two schemes share an access, a drainage outfall, an attenuation basin, an open space or a play area?
• Would either scheme work on its own if the other were refused?
• Were the applications submitted at the same time, or close together, by the same agent?
• Does the layout of one depend on a road or a service corridor shown in the other?

An affirmative answer to several of these makes a single assessment very likely.

Cumulative assessment of related applications

Environmental impact assessment law is the clearest place where splitting is addressed directly. Screening under the Town and Country Planning (Environmental Impact Assessment) Regulations 2017 requires consideration of the project as a whole and of cumulative effects with other development, and the courts have consistently held that a project should not be artificially divided to avoid assessment.

The same logic is applied more broadly in development management, even where no formal rule compels it. An officer assessing highway capacity, drainage, school places or landscape impact will consider the cumulative effect of both schemes, because that is what the material considerations require.

Where the authority concludes that the schemes are one development, the practical result is that the second application is treated as major, with the longer period, the wider publicity and the affordable housing requirement. If the first permission has already been granted, the authority may seek contributions on the second to reflect the cumulative total.

A screening opinion is worth requesting at the outset where there is any doubt. It is free, it produces a written position, and an adverse screening opinion found at validation stage is far more disruptive, which is the point of the Environmental Impact Assessment screening process in the first place.

Common ownership, access and timing as evidence

Ownership is recorded on the application form through the certificates. Certificate A confirms the applicant owns all the land in the application site. Where land outside the red line is owned by the applicant, that ownership is not hidden, since the authority can check the title and frequently does.

Signing a certificate that is false is an offence under section 65 of the Town and Country Planning Act 1990. That is a serious consequence attached to a box most applicants tick without reading.

Access is the most visible evidence. Two schemes served by one new estate road are plainly one development, whatever the red lines say. Where the second scheme relies on a road to be built under the first permission, the dependence is on the drawings.

Timing matters less than the other two but it is noticed. Applications submitted within weeks of each other by the same agent, on adjoining land, with consecutive reference numbers, will be read together.

Consequences when the authority treats the sites as one

The mildest outcome is a request for further information and a reclassification to major, with a new determination date and a request for the documents a major application needs. That costs time rather than the permission.

The harder outcomes are worth understanding. The authority may refuse on the basis that cumulative impacts have not been assessed. A permission granted on misleading information can be challenged by judicial review by a third party, and the authority has revocation powers it rarely uses but does hold. Where a false certificate has been signed, there is a criminal offence in the background.

There is also a reputational cost that is real in practice. Development management teams remember agents who have tried it, and the next application from the same source gets read more carefully.

Where affordable housing has been avoided, authorities sometimes respond on the later application by seeking a contribution reflecting the whole, which is where an honest Affordable Housing Statement covering both phases would have put the applicant in a better position from the start.

Where separate applications are legitimate

Plenty of situations produce two applications on adjoining land for entirely proper reasons.

Different landowners developing separately, with no agreement between them and no shared infrastructure. A site allocation split between two parties who are not connected. A phased delivery under a single outline permission, where the reserved matters applications come forward separately and the cumulative position was already assessed at outline. A scheme where vacant possession of part of the site is years away and the developable part cannot wait.

The distinguishing feature in each is that the earlier scheme was assessed on the whole, or that the schemes are independent in fact as well as on paper. If the second scheme would be unaffected by refusal of the first, the case for separate treatment is strong.

Scale thresholds elsewhere work the same way. Referral thresholds, building height triggers and other scale tests all look at the development rather than the application form, as Greater London Authority referable thresholds illustrate.

Declaring the wider context in the submission

The reliable approach is to put the wider position in the planning statement rather than leaving it to be discovered.

Describe the whole land holding and what is intended on the rest of it. Explain why the applications are separate. Address the cumulative effects on highways, drainage and infrastructure as if the schemes were one. Where the cumulative total would cross a policy threshold, offer the contribution or the affordable provision through a unilateral undertaking.

That sounds like giving away the advantage. In practice it converts a contested question into a negotiation, and it protects the permission from later challenge. An applicant who has disclosed everything and offered a proportionate contribution is in a much stronger position than one whose second application arrives in a planning officer's inbox as a surprise.

Enter your postcode on PlanScope to see which reports a scheme is likely to need at either side of the major development threshold.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.

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