Part 6 agricultural permitted development on a large holding

Part 6 agricultural permitted development splits at five hectares. Class A of Part 6 of Schedule 2 to the Town and Country Planning (General Permitted Development) (England) Order 2015 covers agricultural units of 5 hectares or more and is considerably more generous than Class B, which deals with smaller units. On a large holding you can put up a building of up to 1,000 m² ground area and up to 12 metres high without a planning application, provided it is reasonably necessary for agriculture within that unit and you go through the prior notification procedure.

That is a real right and it is also a narrow one. Most of the arguments about Part 6 come down to three words in the Class A wording: reasonably necessary, agriculture, and unit.

The unit size threshold and the parcel rule

The unit is the agricultural unit, which means the land occupied as a unit for agricultural purposes, not the field you are building in and not your registered title. Tenanted land you farm counts. Land you own and let to someone else does not form part of your unit.

Two traps follow. Class A is not available on a separate parcel of land forming part of the unit which is less than 1 hectare in area, so an outlying half-hectare paddock gets nothing even where the holding runs to 300 hectares. And if the unit drops below 5 hectares, perhaps because a parcel is sold or a tenancy ends, the Class A right goes with it and Class B applies instead, with its much tighter limits.

Keep a plan of the unit with areas, updated when the holding changes. When an officer challenges a Part 6 notification, the first question is almost always about the extent of the unit, and a plan prepared at the time is worth more than a reconstruction afterwards.

Ground area, height and proximity limits

The aggregation rule catches people building in phases. Three 400 m² sheds put up in successive springs within 90 metres of each other breach the limit on the third one, even though each would have been fine in isolation. Count back two years before you notify.

The aerodrome restriction is severe and easy to miss, because 3 kilometres from the perimeter of a small airfield covers a great deal of countryside. Three metres is a height that will not accommodate a modern machinery shed, so check the aerodrome safeguarding position before the design work starts.

Height is measured from ground level, with the usual complication where the ground slopes, and the approach is the same as the one used elsewhere in Schedule 2, set out in measuring height under Part 1 against adjacent ground.

Prior notification of siting, design and external appearance

Class A is not a free pass. Where the development is the erection of a building, an extension or alteration above the threshold the Order sets, the formation or alteration of a private way, or a large excavation or deposit, the developer must first apply to the local planning authority for a determination as to whether its prior approval is required for the siting, design and external appearance of the building, or the siting and means of construction of the way.

The Order calls an extension or alteration significant where the cubic content of the original building would increase by more than 10 per cent, or where the resulting height would exceed the height of the original building.

The procedure, in order:

1. Submit the application with a written description of the proposed development, a plan showing the site and the fee.
2. The authority has 28 days to notify you whether prior approval is required.
3. If it says no, or says nothing within 28 days, you may proceed as notified.
4. If it says yes, you must not begin until approval is given, or until eight weeks have passed from the date of the application without a decision.
5. The development must be started within five years and carried out in accordance with any approved details.

What the authority may consider is limited to siting, design and external appearance, and for a private way to siting and means of construction. It cannot refuse because it doubts the agricultural need, although it can and will ask questions that go to whether Class A applies at all. That is a different point, and it is the one to prepare for. The relationship between prior approval procedures and wider screening requirements is covered in prior approval applications and EIA screening.

Livestock, slurry and the 400 metre rule

Buildings and structures for accommodating livestock, and excavations or structures for storing slurry or sewage sludge, must not be within 400 metres of the curtilage of a protected building. A protected building is broadly a permanent building normally occupied by people, but it does not include buildings within the same agricultural unit, so your own farmhouse does not block your own livestock building.

The condition has a second limb that catches the clever route. A building put up under Class A within 400 metres of a protected building, even if it was notified and built for machinery storage, cannot later be used for livestock accommodation or slurry storage except in the narrow emergency circumstances the Order describes. So you cannot build a general purpose shed close to a neighbouring cottage and populate it with cattle the following year.

Measure from the curtilage of the protected building, not from its wall, and measure to the nearest part of your structure. On marginal cases get the distance surveyed rather than scaled off a mapping application.

What reasonably necessary for agriculture means

Agriculture is defined in section 336(1) of the Town and Country Planning Act 1990 and includes horticulture, fruit growing, seed growing, dairy farming, the breeding and keeping of livestock, grazing land, meadow land, market gardens and nursery grounds, and woodlands ancillary to farming.

Three boundaries matter in practice.

Keeping horses for riding or recreation is not agriculture. Breeding and rearing them can be, which is why equestrian cases turn on the detail of the operation rather than on the presence of horses.

Processing, packing and retailing produce is agriculture only where it remains ancillary to the farming operation. A building for sorting and bagging your own potatoes is likely to qualify. One for processing bought-in produce from other farms is not.

And the building must be reasonably necessary for agriculture within that unit. A machinery store for a contracting business that works other people's land fails on the last three words, however agricultural the machinery looks. If the honest answer is that the building serves a diversified enterprise, Part 6 is the wrong route and a planning application supported by a Planning Statement is the right one.

Excavations, roads and hard surfaces

Class A covers excavation and engineering operations reasonably necessary for agriculture, which brings in reservoirs, drainage, tracks and yard surfaces. Two conditions bite.

Minerals extracted during the works must stay on the unit. You cannot dig out a reservoir and sell the gravel, and doing so converts an agricultural engineering operation into mineral extraction requiring permission.

Waste material must not be brought onto the land from elsewhere for deposit, except for use in the works or in creating a hard surface, and anything brought in must be incorporated into the works straight away. Importing inert material for a track is a recognised route and it is also the one most often abused, which is why authorities investigate it.

Private ways need the prior notification procedure for siting and means of construction, so a new farm track is not simply a matter of getting a digger in.

When the building is later used for something else

Using an agricultural building for a non-agricultural purpose is a material change of use needing permission, and the fact that the building was lawfully erected under Part 6 gives no help at all.

The Order's conversion routes have their own conditions. Class Q for conversion to dwellings and Class R for flexible commercial use both require the building to have been in agricultural use as part of an established agricultural unit at a specified date, and the Order contains provisions designed to stop a building erected under Part 6 being converted shortly afterwards. Check those conditions before putting up a building with conversion in mind, because the timing restrictions are deliberate.

Unauthorised use is also where enforcement arrives. A building notified as a grain store and used as a commercial workshop is a breach of planning control, and the time limits for enforcement action have been changing under the Levelling-up and Regeneration Act 2023, so do not rely on an old four-year rule of thumb. The current position is set out in enforcement time limits for permitted development breaches.

Enter your postcode on PlanScope to see which reports a farm building or diversification scheme 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. A Lawful Development Certificate under section 191 or 192 of the Town and Country Planning Act 1990 is the only formal way to confirm that works or a use are lawful. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.