Reports for a nine unit scheme on a brownfield site
One unit below the major threshold changes the determination period, the consultees and the affordable housing position. Here is the evidence base a nine dwelling brownfield scheme still has to assemble.
Nine dwellings is a deliberate number. A nine unit scheme sits one unit below the major development threshold, and that single unit changes the determination period, the fee, the consultees, the affordable housing position and the amount of evidence a council can reasonably ask for. On a brownfield site the evidence base still has real weight, but it is a minor application pack rather than a major one.
Major development means ten or more dwellings, or a site of half a hectare or more where the number is not yet known, or 1,000 square metres or more of floorspace. Those definitions sit in the Development Management Procedure Order 2015 and they drive most of what follows.
What the tenth unit would cost you
Crossing into major territory brings a longer determination period of 13 weeks rather than eight, a higher fee, and a wider circle of consultees.
Three of those consultees matter in practice. The lead local flood authority becomes a statutory consultee on surface water drainage for major development, which means its comments carry formal weight rather than being an internal view. Active Travel England is consulted on larger majors. And the affordable housing threshold in national policy bites at ten units outside designated rural areas.
There is a cost to staying small, and it is worth naming honestly. A nine unit scheme on a site that could comfortably take twelve is leaving value on the table, and some councils will say so in the officer report. Land economics, not report avoidance, should decide the number.
Contamination on a former commercial use
A brownfield site with an industrial or commercial history is the one place where a minor scheme can carry major-scale technical cost.
Start with a Phase 1 desk study prepared to BS 10175, covering historic mapping, regulatory records, the geological and hydrogeological setting, and a conceptual site model identifying sources, pathways and receptors. If the model shows plausible pollutant linkages, a Phase 2 intrusive investigation follows, with soil, soil gas and where relevant groundwater sampling.
Three things regularly surprise applicants at this scale.
- Residential end use is the most sensitive land use category, so a site that was acceptable as a workshop may need remediation for housing with gardens.
- Ground gas from made ground or a former landfill nearby is assessed over multiple monitoring visits across a range of atmospheric pressures, which takes months rather than weeks.
- Reusing excavated soils on site needs a materials management plan under the industry code of practice, or the soil becomes waste and leaves in lorries.
Land contamination reporting must be carried out by suitably qualified and experienced persons, so a contaminated land assessment is a commissioned report and an AI-assisted draft can only frame it. Expect conditions requiring a remediation strategy and a verification report before occupation.
Drainage and the surface water hierarchy
Brownfield sites usually drain at a high rate because they are largely sealed. That gives you the strongest argument available in drainage design, which is betterment.
The hierarchy is infiltration first, then a watercourse, then a surface water sewer, then a combined sewer. On a former yard or works, infiltration may be ruled out by contamination rather than by soils, because pushing water into contaminated ground is unacceptable. Where discharge to a sewer is the only option, the undertaker will normally expect a restricted rate, and a reduction against the existing brownfield rate is usually achievable and usually welcomed.
A Drainage Strategy at this scale needs the existing and proposed impermeable areas, the discharge rate and its justification, attenuation volumes for the design event including a climate change allowance, exceedance routing, and a maintenance plan for whatever is proposed. Check the current Environment Agency climate change allowances rather than reusing a figure from an older scheme, because they are revised.
Biodiversity net gain on a hard surfaced baseline
The biodiversity gain condition applies to small sites, so a nine unit scheme needs a biodiversity gain plan approved before development begins unless an exemption applies.
The arithmetic on a sealed site is kinder than on a green one. Fully sealed surfaces score no biodiversity units, so the ten per cent uplift is calculated from a low base and is frequently deliverable on site through planting, green roofs, hedgerow creation and landscape margins. What upsets that calculation is the strip of self-seeded scrub or ruderal vegetation along a boundary, which scores something and has to be replaced like for like or better under the trading rules.
Survey the whole site rather than the development footprint. And get the baseline measured before any clearance, because a site degraded after 30 January 2020 is assessed at its earlier value.
Transport evidence at this scale
Nine dwellings generate few vehicle movements, and a full Transport Assessment is disproportionate. A Transport Statement is the normal document, covering the access arrangement, visibility, parking provision against the local standard, cycle and refuse storage, and a short trip generation comparison against the previous use.
The comparison is the useful part on a brownfield site. A former trade counter or small workshop often generated more movements, including heavy goods vehicles, than nine houses will, and setting that out plainly heads off a highways objection before it forms.
PlanScope flags a Transport Assessment at 50 or more units or 2,500 square metres or more of floorspace. Those are the thresholds the product uses to prompt reports, and the council's validation list and the highway authority's own requirements take precedence over them.
Noise from the neighbours you are moving next to
Brownfield sites in mixed areas raise the agent of change principle. If you introduce housing next to an existing business, the responsibility for mitigating the effect of that business falls on the new development rather than on the established use.
That means a baseline noise survey covering the operating hours of the neighbouring use, internal levels assessed against the relevant British Standard for dwellings, plant noise assessed against background using the industrial and commercial sound methodology, and a glazing and ventilation specification that works alongside the overheating strategy. A Noise Impact Assessment is a report type where councils expect a suitably qualified acoustician, and professional review before submission is strongly advised.
Survey timing matters. A noise survey during a factory shutdown or a school holiday will be challenged.
Affordable housing and the small site threshold
National policy sets the affordable housing threshold at major development, so schemes of fewer than ten dwellings are not normally asked for on-site provision or a contribution. The exception is designated rural areas, where authorities may apply a lower threshold of five units or fewer.
Check the adopted local plan rather than assuming. Some plans contain policies that predate the national threshold, and vacant building credit may also be relevant on a brownfield site with existing floorspace.
Sequencing the evidence base
Commission in an order that lets each piece inform the next.
- Phase 1 contamination desk study and a topographical survey, before the layout.
- Drainage investigation, including infiltration testing where contamination allows it.
- Biodiversity baseline survey, before any site clearance.
- Noise survey, timed to the neighbouring use rather than to the programme.
- Phase 2 intrusive investigation, once access and layout allow.
- The written statements last, describing decisions rather than driving them.
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. This is general guidance rather than legal advice, so check your council's validation list before you submit. Enter your postcode on PlanScope to see which reports a brownfield site is likely to need.
Frequently asked questions
What changes at ten dwellings?
Ten or more dwellings is major development under the Development Management Procedure Order 2015. That brings a 13 week determination period instead of eight, a higher fee, the lead local flood authority as a statutory consultee on surface water, and the national affordable housing threshold. A nine unit scheme sits below all of them.
Does biodiversity net gain apply to a nine unit scheme?
Yes, under the small sites regime that began on 2 April 2024, unless an exemption applies. A fully sealed brownfield surface scores no biodiversity units, so the ten per cent uplift is calculated from a low base and is often deliverable on site. Self-seeded scrub along boundaries is what complicates the arithmetic.
Is a transport assessment needed for nine houses?
Normally no. A transport statement covering access, visibility, parking against the local standard, cycle and refuse storage and a trip comparison against the previous use is usually proportionate. On a brownfield site the previous commercial use often generated more movements, including goods vehicles, than nine houses will.
What is the agent of change principle?
Where a new development is introduced next to an existing business, the responsibility for mitigating the effect of that business falls on the new development rather than the established use. On a mixed brownfield site that means baseline noise surveys timed to the neighbour's operating hours and a glazing and ventilation specification to match.
Will a nine unit scheme be asked for affordable housing?
Usually not. National policy sets the threshold at major development, so schemes of fewer than ten dwellings are not normally asked for provision or a contribution. Designated rural areas are the exception, where a lower threshold of five units or fewer may apply. Check the adopted local plan rather than assuming.
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.