Technical details consent and what it must cover

Technical details consent is the second stage of the permission in principle route, and granting it is what actually gives you planning permission. Permission in principle settles three things and no more: the location, the land use and the amount of development. Everything else, from layout and access to drainage, ecology and contamination, is decided at the technical details stage. That split is narrower than the outline and reserved matters arrangement most self-builders are used to, and it cuts both ways. The council cannot reopen the principle. It can refuse on almost anything else.

How the second stage relates to the first

Permission in principle was introduced by the Housing and Planning Act 2016, which inserted section 58A into the Town and Country Planning Act 1990. It comes from one of two places: an entry on a council's brownfield land register, or an application made to the local planning authority.

The application route is limited to minor housing-led development, meaning fewer than 10 dwellings on a site below one hectare. Development requiring environmental impact assessment cannot use the route, and nor can development that would need an appropriate assessment under the habitats regime.

What the permission in principle grants is narrow. It fixes that housing is acceptable here, on this land, at roughly this quantum. It says nothing about what the houses look like, where the access goes or how surface water is dealt with.

Technical details consent is then applied for separately. On grant, planning permission for the development comes into existence. There is no third stage.

What the authority may not revisit

This is the point of the route, and it is worth being precise about it.

When determining a technical details consent application, the authority must not go behind the in principle matters. It cannot decide that the site is unsuitable for housing after all, or that eight dwellings is too many when the permission in principle said eight.

What it can do is assess everything else on its merits, and refuse if the details are unacceptable. Layout, scale, appearance, access, parking, drainage, amenity for neighbours and future occupiers, trees, ecology, heritage impact, land contamination, highway safety.

Compare that with outline permission and reserved matters. An outline application can fix as much or as little as the applicant chooses, with reserved matters limited to access, appearance, landscaping, layout and scale, and the outline itself often carrying conditions that shape the later submission. Permission in principle is a blunter instrument: three matters fixed, everything else open.

What the application has to contain

A technical details consent application is, in substance, a full application. The council's validation list applies, and so do the national requirements.

For a small housing site that usually means:

1. Application form, ownership certificates and the correct fee.
2. Location plan and site plan at recognised scales, with existing and proposed levels.
3. Floor plans, elevations and sections for each house type.
4. A Planning Statement addressing the development plan policies that bear on the detail.
5. A design and access statement where the local list requires one.
6. Drainage and surface water information, with infiltration testing results where soakaways are proposed.
7. Ecology information, including a preliminary appraisal and any species survey the site warrants.
8. Arboricultural information where trees are present or adjoining.
9. Highways information covering access geometry, visibility splays and parking.

Check the council's validation list before you submit rather than after. Because technical details consent is less familiar than a full application, validation teams sometimes apply the full application list by default, and it is easier to supply a document than to argue about it.

Determination periods and fees

The statutory period for determining a technical details consent application is five weeks for minor development, which is shorter than the eight weeks for a minor full application. For major development it is ten weeks.

That shorter period is one of the route's real advantages, and it is also a reason the council may ask for an extension of time where consultee responses are slow. Agree an extension rather than letting the period expire, because a non-determination appeal on detail is rarely a good use of six months.

Fees for both stages are set by the current planning fee regulations. The permission in principle fee is calculated by site area, and the technical details fee is calculated as for a full application. The figures are indexed annually, so check the current schedule rather than a number quoted in an older guide.

Conditions at the technical details stage

Technical details consent can be granted subject to conditions, including pre-commencement conditions, in the same way as a full permission.

Expect conditions on materials, levels, drainage details, construction management, landscaping and ecological mitigation. Where the site is in a flood zone or near a watercourse, expect drainage conditions with a discharge rate attached.

Biodiversity net gain applies. The biodiversity gain condition operates at the technical details stage, so the metric, the baseline and the gain plan belong in that submission rather than at the permission in principle stage where habitats were never assessed. The note on the biodiversity gain plan sets out what the plan has to contain and when the authority approves it.

That sequencing catches people out. A permission in principle granted on a grassland field says nothing about the habitat baseline, and the baseline has to be established before any clearance takes place.

When the permission in principle expires

A permission in principle granted on application lasts three years from the date it takes effect, unless the authority directs otherwise. One granted through a brownfield land register entry lasts five years.

If no technical details consent is granted within that period, the permission in principle lapses and the principle has to be established again. There is no equivalent of a section 73 application to extend it.

Three years sounds comfortable. It is not, if the site needs a survey season for ecology, an infiltration test that has to wait for winter groundwater, and a pre-application discussion on access with a highway authority running a six month queue.

Programming the two stages together

The route works best where the principle is the uncertain part. A paddock on the edge of a settlement where the policy position is arguable is a good candidate. A serviced plot in an established estate is usually better served by a single full application.

An illustrative sequence for a four dwelling site:

1. Pre-application discussion on the principle, two months.
2. Permission in principle application, determined in five weeks.
3. Ecology appraisal and any seasonal survey, up to a full season depending on the month.
4. Design, drainage and highways work, three to four months.
5. Technical details consent application, determined in five weeks plus any agreed extension.

Note where the risk sits. The permission in principle does not guarantee that a scheme of that size can be laid out acceptably on the land. If the access cannot achieve visibility, or the drainage cannot discharge, the technical details consent can be refused on those grounds and the permission in principle will not save it.

To see which supporting documents a small housing site is likely to need at the technical details stage, browse the report types by category, or enter your postcode on PlanScope to see what the site's constraints suggest.

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.