Nine units against ten and the affordable housing line

The nine units affordable housing threshold question has a clear national answer and a messy local one. National policy in the current National Planning Policy Framework, published 17 August 2026, is that affordable housing should not be sought from development that is not major development, and major residential development means ten or more dwellings. So a nine unit scheme in most of England carries no affordable housing requirement and no section 106 obligation for it.

The messy part is everything around that sentence: designated rural areas where the line falls at five, local plan policies that predate the national threshold, and the question of whether a site split into two parcels is really one development.

Where the national policy line falls

Major development is defined in article 2 of the Development Management Procedure Order 2015. For housing it means the provision of ten or more dwellings, or, where the number of dwellings to be provided is not known, a site of 0.5 hectares or more.

Read the second limb carefully, because it is routinely misapplied. It bites only when the number is unknown, which in practice means an outline application for an unspecified quantum. State nine dwellings on the form and the scheme is a minor application even on a one hectare site. Officers sometimes assert otherwise, and the answer is to quote the definition rather than argue about it.

Above that line, an Affordable Housing Statement setting out the policy requirement, the tenure split and the distribution across the site becomes part of the submission.

Local plan policies that set a lower figure

Section 38(6) of the Planning and Compulsory Purchase Act 2004 requires determination in accordance with the development plan unless material considerations indicate otherwise, and national policy is a material consideration rather than the plan itself. That is the source of the conflict.

Plenty of adopted local plans still carry affordable housing thresholds of five dwellings, or in some rural authorities one dwelling, adopted before the national threshold was introduced. Where the plan is recent and its evidence base justifies the lower figure, the authority will apply it. Where the policy is old and the plan predates the national position, applicants argue that the policy is out of date and national policy should prevail.

Inspectors have taken different views depending on the age of the plan, the strength of the local evidence and the specifics of the scheme, so treat appeal decisions as indications of approach rather than as precedent. The practical step is to read the policy, check the plan's adoption date, and ask the officer at pre-application stage what the authority's current position is, in writing.

Designated rural areas and reduced thresholds

In designated rural areas, National Parks and National Landscapes, national policy allows policies to set a lower threshold of five units or fewer. In those areas a scheme of six to ten dwellings can be asked for a financial contribution towards affordable housing instead of on-site units, commonly payable after completion.

Designated rural areas are those designated under section 157 of the Housing Act 1985, which is not a designation most people can recall for their own district. Check it before assuming the ten unit line applies, because a nine unit scheme in a designated parish can carry a contribution while an identical scheme five miles away carries none.

Vacant building credit and how it applies

Where a vacant building is brought back into use or demolished and replaced, national policy provides a credit equivalent to the existing gross floorspace of the vacant building, applied against the affordable housing requirement. On a conversion scheme the credit can extinguish the requirement entirely.

Authorities test three things: whether the building was vacant in fact rather than emptied to trigger the credit, whether it has been abandoned, and what the floorspace actually is. Evidence means business rates records, marketing particulars, utility accounts, dated photographs and a floor area schedule measured to a stated standard. The detail of vacant building credit matters more than the principle, because most disputes are about the evidence rather than the policy.

Splitting a site and the cumulative question

Two applications of five dwellings each on adjoining parcels in the same ownership will be read as one scheme. The signals are obvious from the documents: a shared access, a single drainage strategy, one landowner, a boundary drawn through the middle of a field, applications submitted in the same week.

There is no general anti-avoidance rule, and each application is determined on its own merits. What the authority can do is conclude, as a matter of fact, that the development being proposed is a single scheme of ten or more dwellings and apply policy accordingly. It can also refuse the second application on the basis of the cumulative position.

Real phasing over years, with separate access and a real gap in time, is a different situation. So is a second application prompted by a change of circumstances. The distinction is about the facts rather than the labels.

What actually changes at ten

Biodiversity net gain is in that table to make a point. The small sites regime has applied since April 2024, so the biodiversity gain condition, the statutory metric and the gain plan are the same problem at nine units as at ten. Dropping a unit does not avoid it.

The consultee list is the other underrated difference, and it is worth knowing the consultees that appear once a scheme becomes major, because each one adds time as well as evidence.

Evidence the authority will look for

On a nine unit application in an area with a lower local threshold, expect the officer to ask for the affordable housing position to be addressed rather than ignored. A short section in the planning statement that states the national threshold, the local policy, the plan's adoption date and your conclusion is enough to put the issue on the table properly.

Where a contribution is sought and the scheme cannot carry it, the route is a Viability Assessment prepared to the approach in national guidance, with the expectation that it will be published and independently reviewed. That is a real cost and a real delay, which is part of the calculation below.

Housing mix is the other question that follows. At this scale the authority will look at the balance of house sizes against its own evidence, and housing mix and space standards tighten as schemes grow.

Whether nine units is worth the compromise

Run the arithmetic rather than the instinct. The tenth unit brings gross development value, and the affordable requirement applies to the whole scheme rather than to that unit alone, so on a policy requirement of 30 or 40 per cent the cost of crossing the line can exceed the value of the extra home.

Against that, set the things a nine unit scheme gives up. Plot sizes and layout quality on a site that naturally takes twelve. The awkwardness of a scheme that has been squeezed to a number rather than designed. And the risk that the authority treats the nine unit application as the first phase of a larger site and refuses it as premature to a whole-site scheme.

Illustrative example. A 0.55 hectare site with an adopted policy requiring 30 per cent affordable housing on major schemes. Nine open market houses avoids the requirement, the major fee band and the press notice, and can be determined in eight weeks. Twelve houses triggers roughly four affordable units or a commuted sum, a 13 week period, a section 106 and probably a viability discussion. The nine unit scheme is often the better business case, and it is the worse scheme on the ground if the layout has to be contorted to reach the number.

Decide it before the layout is drawn, and write down which it is.

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

Enter the site postcode on PlanScope to draft the planning statement and, where the threshold applies, the Affordable Housing Statement for your scheme. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.