Part 6: agricultural development on units of 5 hectares or more

Class A of Schedule 2 Part 6 of the Town and Country Planning (General Permitted Development) (England) Order 2015 permits the carrying out on agricultural units of 5 hectares or more of works for the erection, extension or alteration of a building, and excavations and engineering operations, where they are reasonably necessary for the purposes of agriculture within that unit. It is one of the most useful rights in the Order and one of the most conditioned.

Almost every dispute about it turns on the same three things: the size of the unit, the aggregation rule, and whether the building is really for farming.

What Class A permits on larger agricultural units

Two limbs sit inside Class A. The first covers buildings, meaning erection, extension or alteration, along with certain other operations. The second covers excavations and engineering operations, including private ways, tracks and hardstandings, again where reasonably necessary for agriculture.

The phrase reasonably necessary for the purposes of agriculture within that unit does a lot of work. The building must serve agriculture on that unit, not on land elsewhere, and not a business that happens to be run from a farm. A machinery store for a contracting business operating across other people's land is not covered.

Agriculture takes its meaning from section 336(1) of the Town and Country Planning Act 1990, which brings in livestock, crops, grazing land and market gardens, and leaves out equestrian uses other than the grazing of horses on agricultural land.

Note the unit, not the field. The 5 hectare threshold applies to the agricultural unit as a whole, and land held under different tenures may or may not form a single unit depending on how it is occupied.

Floorspace, height and proximity limits

The Order sets numerical limits, and they are the part most likely to have been amended, so take them from the current text of Part 6 rather than from any summary.

The limits to check, in order:

1. The maximum ground area a building may cover under the class.
2. The aggregation rule, which reduces that allowance by the ground area of any building erected or extended within a stated distance and within the preceding two years.
3. The general height limit, and the reduced height limit for a building within 3 kilometres of the perimeter of an aerodrome.
4. The prohibition on siting a building within 25 metres of the metalled part of a trunk or classified road.
5. The restriction preventing a building for accommodating livestock, or for storing slurry or sewage sludge, within 400 metres of the curtilage of a protected building.

The aggregation rule catches more farms than any other. A unit that put up a 500 square metre store eighteen months ago has that area counted against a new building nearby, and the answer is either to wait, to move the new building outside the aggregation distance, or to apply for planning permission.

The 400 metre livestock rule is the other frequent problem. A protected building is broadly a permanent building normally occupied by people, and neighbouring dwellings often sit closer than the distance allows.

The prior notification procedure and the 28 day period

Prior notification is not a planning application in the ordinary sense. You are asking the council to decide whether its prior approval is required for a defined set of matters.

The process runs like this.

Submit a written description of the proposed development, a plan showing the site, and the fee. The council then has 28 days from receipt to notify you either that prior approval is not required, or that it is required, or to give notice that approval has been granted or refused.

If the council says approval is not required, or says nothing within the period, the development may go ahead in accordance with the details submitted. If it says approval is required, you provide the further detail and the council determines it.

Two practical points. The 28 day clock only starts on a valid submission, so an incomplete notification does not start it at all. And the development must be carried out in accordance with the details submitted, so a building put up in a different position from the one notified is not permitted development.

Development under the class must also begin within a period stated in the Order after the council's determination, so do not treat an old notification as a permanent entitlement.

Reasonably necessary for agriculture: what has to be shown

Councils do test this, particularly where a farm has been building steadily or where the proposed building looks more like a workshop than a store.

Support the notification with a short statement covering the extent of the holding, the enterprise, the existing buildings and their use, what the new building is for, and why the existing buildings cannot accommodate it. Where the need arises from a change in the farming operation, say what changed.

Where the case is finely balanced, a short Planning Statement explaining the agricultural need does more good than any amount of correspondence afterwards.

Councils also look at the pattern. Several notifications in quick succession on the same unit, particularly for buildings sited away from the farmstead and close to a road, will attract attention.

Smaller units between 0.4 and 5 hectares under Class B

Class B applies to agricultural units of not less than 0.4 hectares and less than 5 hectares. It is a much narrower right.

Broadly, Class B permits the extension or alteration of an existing agricultural building, the provision, rearrangement or replacement of a sewer, main, pipe, cable or other apparatus, the provision, rearrangement or replacement of a private way, the creation of a hardstanding, and the deposit of waste material, all subject to their own limits.

What it does not permit is a new agricultural building. Owners of smallholdings frequently discover this after buying the land, and the answer is a full planning application judged against the local plan's countryside policies.

Below 0.4 hectares there is no agricultural permitted development, and there is no threshold that grows the unit by adding a rented field for a season.

Excavations, tracks and external appearance

Engineering operations under the class cover farm tracks, hardstandings, reservoirs, and excavations reasonably necessary for agriculture. For a private way the prior approval matters are siting and means of construction, which in practice means the route and the surfacing.

Tracks generate more objections than buildings, because they are visible in the landscape and because they are often the first sign to neighbours that something is happening. Where a track crosses a watercourse or alters drainage patterns, the arrangements belong in a Drainage Strategy even though the Order does not require one, because the council will ask.

Where a new or improved access onto a public road is involved, that is a separate matter from Part 6, and highway consent will be needed. A short Transport Statement covering visibility and vehicle movements answers the question early.

Ecology also sits outside the Order. Barn owls, bats and nesting birds are protected by law regardless of what Part 6 permits, and a Preliminary Ecological Appraisal before demolition or alteration of an older building avoids an offence.

Where a full application is unavoidable

Several situations take you outside the class. A unit below 5 hectares wanting a new building. A building over the ground area cap or inside the aggregation distance. A livestock building within 400 metres of a dwelling. A building intended for a non-agricultural business. A holding where the right has been removed by an Article 4 direction or by condition on an earlier permission.

There is also a condition worth understanding at the outset. Where a building erected under the class ceases to be used for agriculture within ten years of substantial completion, and no permission for another use is granted, the Order can require its removal and the restoration of the land. That is why treating Part 6 as a route to a future conversion is a poor plan.

Enter your postcode on PlanScope to see which supporting reports a farm building or track proposal is likely to need.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it, and remember that a lawful development certificate is the only formal way to confirm that works are lawful. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.