Which reports nine dwellings need and which ten do
At ten dwellings an application becomes major, with a longer period, wider publicity and an affordable housing requirement. Biodiversity, flood and ecology evidence does not change.
Nine or ten dwellings is the reports threshold that matters most to a small developer, because ten is the line at which an application becomes major development. Nine dwellings is a minor application with an eight week determination period. Ten is a major application with 13 weeks, newspaper publicity, a design and access statement and, in most areas, an affordable housing requirement.
What does not change is more interesting than what does. Biodiversity net gain applies either side of the line. Flood risk evidence follows the site's flood zone and area, not the unit count. Ecology surveys depend on what is on the site. So the extra burden at ten units is procedural and policy based rather than technical.
What changes at the ten unit line
Set the two scenarios out plainly.
| Nine dwellings | Ten dwellings | |
|---|---|---|
| Application type | Minor | Major |
| Determination period | 8 weeks | 13 weeks |
| Publicity | Site notice or neighbour letters | Newspaper notice as well |
| Design and access statement | Not required by the major limb | Required |
| Affordable housing | Not normally sought | Normally sought, policy dependent |
| Committee likelihood | Lower under most delegation schemes | Higher |
| Fee basis | Per dwelling, minor band | Per dwelling, major band |
The definition sits in article 2 of the Development Management Procedure Order 2015, which treats the provision of ten or more dwellings as major development. It also catches a site of 0.5 hectares or more where the number of dwellings is not stated, which matters on an outline application that leaves the quantum open.
Our note on the reports needed at the ten unit major threshold works through the major scenario in full. What follows is the comparison, and the budgeting question that comes with it.
The determination period and publicity
Five extra weeks sounds modest and rarely is, because the period sets the rhythm of everything else.
On a major application the authority has longer, so consultees have longer, and the officer will not usually begin drafting a report until the consultation period has closed and the statutory consultees have responded. Extensions of time are also more common on majors, agreed by email and quietly adding weeks.
Newspaper publicity brings a second effect. A notice in the local paper reaches people a site notice does not, which raises the likelihood of organised objection and therefore of a committee referral. On a sensitive site that is worth factoring into the programme as a real risk rather than a formality.
For a self-builder with finance costs running, the practical gap between a minor and a major application is often three to four months rather than five weeks.
Affordable housing evidence at ten units
This is the substantive policy change, and it is the one that affects the appraisal.
National policy provides that affordable housing contributions should not be sought from developments below a threshold of ten homes, or a floorspace equivalent, with the important exception that authorities in designated rural areas may apply a lower threshold. So the first check is not the unit count. It is whether your site sits in a designated rural area where the local plan applies a threshold of five, or even fewer.
Where the requirement applies, the scheme needs an Affordable Housing Statement setting out the quantum, the tenure split against the policy, the unit mix and the delivery mechanism, whether on site provision or a commuted payment where the policy allows it. Where the requirement cannot be met in full, that is a viability argument with its own evidence base, and it is not a conversation to open at validation stage.
The design and access statement requirement also arrives at ten units, so a Design and Access Statement covering layout, scale, appearance, landscaping and access becomes part of the submission rather than an optional extra.
Biodiversity net gain applies either way
The biodiversity gain condition applies to small sites as well as majors, with the small site arrangements having come into effect after those for major development. Ten per cent gain, a 30 year management period, and a biodiversity gain plan approved by the authority after permission and before development begins.
The practical difference is the tool rather than the obligation. A small sites metric is available where the development meets the criteria for its use, which generally means a limited number of dwellings, a site below one hectare and no effect on priority habitat. It is simpler to complete, and for a nine unit scheme on a modest plot it is usually the route.
Either way the baseline needs a habitat condition assessment in the botanical season, and either way the metric and the gain plan have to be prepared by a competent person under the Environment Act 2021 framework. A Biodiversity Net Gain Assessment draft is a starting point for that professional, not a substitute for their survey work or sign-off.
Do not treat nine units as a way round biodiversity obligations. It is not.
Drainage and flood evidence follow site area, not unit count
Flood risk evidence is triggered by the flood zone and by site area. A site in Flood Zone 2 or 3, or of one hectare or more, needs a flood risk assessment whether it carries nine dwellings or ten.
Surface water drainage works the same way. The lead local flood authority is a statutory consultee on major development, which is a procedural difference, but the design obligation to manage surface water and restrict discharge rates does not disappear below ten units. Many authorities require a drainage strategy on any new residential development through their local validation list.
Foul drainage, water supply and contaminated land evidence are all driven by site circumstances too: the presence of a sewer, the previous use of the land, the ground conditions. None of them changes at the ten unit line.
The honest summary is that the technical evidence base is set by the site, and the procedural burden is set by the unit count.
Transport evidence at this scale
Neither scheme reaches the thresholds at which a full transport assessment is usually required, which are generally expressed at a far larger scale, and our note on when a transport assessment is triggered sets out where those lines fall.
What both schemes need is proportionate: a transport statement or a short technical note covering access geometry, visibility splays, trip generation, parking provision against the local standard, cycle parking, refuse collection and construction access. On a ten unit scheme in a constrained location the highway authority will look harder, and a travel plan is sometimes requested.
Visibility splays are the item that most often forces a layout change at this scale. Establish the required dimensions with the highway authority before the layout is fixed, because retrofitting a splay usually means losing a plot.
Budgeting the two scenarios
For a scheme hovering at the line, there are three realistic options and they have different costs.
Build nine and keep the minor route. Saves the affordable housing contribution where the threshold applies, shortens the programme, reduces the document list by the design and access statement, and lowers the chance of committee. Costs you a unit of revenue.
Build ten or more and accept the major route. Adds the affordable obligation, the longer period, the newspaper notice, the design and access statement and more consultee engagement. Makes sense where the extra units outweigh those costs, which on a scheme of any density they often do.
Build nine now and more later. Tempting and usually a mistake. An authority will look at whether a site is being artificially subdivided to avoid a policy threshold, and a second application on the same land is assessed with the first in mind. Where the land is plainly capable of more, expect the affordable housing policy to be applied to the cumulative total.
The measurement discipline matters as much as the decision. Count the units the way the policy counts them, check whether your site falls in a designated rural area, measure the site area to two decimal places from the survey, and confirm the fee band against the current schedule rather than a previous application.
Decide which side of the line you are on before commissioning anything, because the affordable housing position changes the appraisal and the appraisal changes the scheme. Browse all 66 PlanScope report types to see what each scenario needs.
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.
Frequently asked questions
What makes an application major at ten dwellings?
Article 2 of the Development Management Procedure Order 2015 defines the provision of ten or more dwellings as major development. It also catches a site of 0.5 hectares or more where the number of dwellings is not stated, which applies to outline applications leaving the quantum open. Major status brings a 13 week determination period instead of eight.
Is affordable housing really not sought below ten units?
National policy sets a threshold of ten homes or a floorspace equivalent, below which contributions should not normally be sought, but authorities in designated rural areas may apply a lower threshold such as five. Check whether the site falls in a designated rural area before assuming a nine unit scheme avoids the requirement.
Does biodiversity net gain apply to a nine unit scheme?
Yes. The biodiversity gain condition applies to small sites as well as major development, with the same 10 per cent gain and 30 year management period, and a gain plan approved after permission and before works begin. The difference is that a simpler small sites metric may be available where the development meets the criteria for its use.
Does a nine unit scheme need a flood risk assessment?
It depends on the site, not the unit count. A flood risk assessment is expected where the site is in Flood Zone 2 or 3, or where the site is one hectare or more. Surface water drainage requirements and contaminated land evidence are likewise driven by site circumstances and local validation lists rather than by major or minor status.
Can I apply for nine now and more later?
You can, but authorities look closely at whether a site is being subdivided to avoid a policy threshold, and a second application is assessed with the first in mind. Where the land is plainly capable of more units, expect the affordable housing policy to be applied to the cumulative total rather than to each application separately.
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.