New agricultural buildings under Part 6

A new agricultural building on a holding of five hectares or more is usually permitted development under Part 6 of the General Permitted Development Order 2015, provided it stays within the size and siting limits and the farmer first obtains a determination on whether prior approval of siting, design and external appearance is required. Agricultural building prior notification is not a planning application and the council cannot refuse it on policy grounds, but it can control where the building sits and what it looks like.

Holdings below five hectares are treated very differently, and that threshold is where most disappointment begins.

What Part 6 permits on a holding of five hectares or more

The main class covers development on agricultural land comprised in an agricultural unit of five hectares or more, where the works are reasonably necessary for the purposes of agriculture within that unit.

It covers the erection, extension or alteration of a building, the formation or alteration of a private way, excavations and the deposit of waste, and works for certain agricultural purposes. The limits that matter in practice are:

• The ground area covered by the building must not exceed 465 m², and that figure aggregates with any building erected under the same class within 90 metres in the preceding two years.
• Height is limited to 12 metres generally, reduced to three metres within three kilometres of the perimeter of an aerodrome.
• No part of the development may be within 25 metres of the metalled portion of a trunk or classified road.
• A dwelling is never permitted.
• Buildings for the accommodation of livestock, and structures for storing slurry or sewage sludge, are not permitted within 400 metres of the curtilage of a protected building.

The 465 m² aggregation rule is the one that catches expanding farms. Two 300 m² buildings put up 18 months apart within 90 metres of each other do not both benefit from the class.

Units below five hectares

Where the agricultural unit is smaller than five hectares, a separate and much narrower class applies. It does not permit new agricultural buildings at all.

What it does permit is limited to extending or altering an existing agricultural building, installing plant or machinery, providing or replacing a private way, providing a hard surface, and similar works, each with its own limits. Anyone with a smallholding who wants a new barn is applying for planning permission, not notifying.

Note also that the holding is the agricultural unit, which can comprise several parcels in the same occupation. Land let to someone else on a separate agricultural tenancy is not part of your unit, and the rules on who applies and which notices are served matter here, as set out in the guide to tenancies, ownership certificates and notices.

The prior notification procedure

The procedure is short and procedurally strict.

1. Submit an application to the local planning authority for a determination as to whether prior approval of siting, design and external appearance is required, with a description of the development, a plan showing the siting, and the fee.
2. Display a site notice, and keep it in place for the period required by the Order.
3. The authority has 28 days from receipt to notify you that prior approval is not required, to notify you that it is required, or to say nothing.
4. If the authority says prior approval is not required, or says nothing within 28 days, the development may proceed as described in the notification.
5. If prior approval is required, the authority then considers siting, design and external appearance and issues a decision.

Two points about step four. Proceeding on the basis of silence is lawful, but you must have submitted a valid application with the correct information and fee, and you must build exactly what you notified. And the development must begin within the period specified in the Order and be completed in accordance with the details approved or notified.

What siting, design and external appearance actually covers

The council's discretion is confined to those three matters. It cannot refuse because it thinks the farm does not need the building, or because the local plan discourages development in open countryside.

In practice the matters raised are: moving the building closer to an existing group of farm buildings rather than into an open field, reducing the visual effect on a nearby National Landscape or conservation area, choosing dark recessive colours for cladding and roof sheets, and planting to soften the profile.

The sensible approach is to design out the objection before submitting. A building tucked against an existing range, in olive green or juniper green profiled sheeting, with a hedge on the exposed side, rarely attracts a prior approval requirement. A pale grey shed in the middle of a field on a ridge line almost always does.

Protected species are a separate matter. Where the works involve demolishing or altering an existing building, or removing a hedge, the wildlife legislation applies regardless of permitted development status, and a bat survey by a licensed ecologist may be needed before anything is touched.

Livestock, slurry and the 400 metre rule

The 400 metre restriction around protected buildings is measured from the curtilage of the protected building, and a protected building is broadly a permanent building normally occupied by people, with exceptions for buildings on the same agricultural unit.

It applies to buildings used for accommodating livestock and to structures for storing slurry or sewage sludge. A general purpose store within 400 metres is permitted, but the moment it is used for livestock the permitted development basis falls away.

Separate regulatory regimes apply alongside planning for slurry storage, including the rules on nitrate vulnerable zones and farming rules for water. Those are enforced by the Environment Agency rather than by the council, and permitted development status gives no immunity from them.

Where planning permission is needed instead

You are applying for permission if the building exceeds 465 m² of ground area, if the unit is under five hectares, if the building is a dwelling, if it is within 25 metres of a classified road, if it is for livestock within 400 metres of a protected building, or if the land is not in agricultural use as part of an agricultural unit.

You are also applying if the use is not agriculture. Equestrian use beyond the grazing of horses is not agriculture, so a stable block, a menage or a livery yard needs permission. Farm shops, processing beyond what is ancillary, and storage for an unrelated business are all outside the class as well, which is the most common reason a Part 6 notification is challenged later.

One more consideration for anyone thinking ahead. A building erected under Part 6 cannot be converted to a dwelling under the agricultural conversion right for ten years after it is built, so putting up a new barn with a view to converting it shortly afterwards does not work. Field shelters and movable structures raise a different question again, covered in field shelters: development, caravans or neither.

Measure the holding, measure the ground area, check the distance to the nearest classified road and the nearest protected building, and only then decide whether you are notifying or applying. You can also check which supporting documents a farm building application needs if the answer turns out to be a planning application.

This is general guidance, not legal advice. A lawful development certificate is the only formal way to confirm that works are lawful, and permitted development limits are detailed, so 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.