Agricultural units and the five hectare permitted line

Agricultural unit permitted development turns on two numbers. Part 6 of Schedule 2 to the GPDO 2015 grants the fuller set of rights, under Class A, on agricultural units of 5 hectares or more. Units of at least 0.4 hectares but less than 5 hectares get a narrower set under Class B, which allows extensions and alterations to existing buildings rather than new ones. Below 0.4 hectares there are no Part 6 rights at all.

Both classes are qualified by the same phrase, and it does more work than the acreage. The development must be reasonably necessary for the purposes of agriculture within that unit.

How the GPDO defines an agricultural unit

The Order defines an agricultural unit as agricultural land occupied as a unit for the purposes of agriculture, and it brings in any dwellinghouse or other building on that land which is occupied for the purposes of farming it.

Three points follow that people get wrong.

The unit is defined by occupation, not by ownership. Land you farm under a tenancy or a grazing licence can form part of the unit, and land you own but have let out to somebody else generally does not. Where the acreage matters, the evidence is the occupation arrangement rather than the title.

The unit has to be occupied as a unit. Two parcels ten miles apart, farmed by the same person as one business, can be one unit, but the further apart and the more separately managed they are, the harder that becomes to sustain.

And agriculture has a statutory definition in section 336(1) of the Town and Country Planning Act 1990, covering horticulture, fruit growing, seed growing, dairy farming, livestock breeding and keeping, the use of land as grazing land, meadow land, osier land, market gardens and nursery grounds, and the use of land for woodlands where ancillary to farming.

That definition is where hobby operations fall out. Grazing land is agriculture. Keeping horses for riding, liveries and equestrian businesses generally is not, because the animals are not being kept for an agricultural purpose. A paddock with two ponies and a field shelter is usually outside Part 6 entirely.

What changes at five hectares

Class A, on units of 5 hectares or more, permits the carrying out of building or engineering operations reasonably necessary for agriculture, subject to limits. The main ones are a ground area not exceeding 1,000 m2 for the works, a height limit of 12 metres, reduced to 3 metres within 3 kilometres of the perimeter of an aerodrome, and a restriction on any part of the development being within 25 metres of a metalled part of a trunk or classified road.

Class A excludes dwellings, and it excludes buildings for accommodating livestock or storing slurry or sewage sludge within 400 metres of the curtilage of a protected building, which broadly means a building in permanent residential or institutional use other than one on the unit itself.

Class B, on units of at least 0.4 hectares and less than 5 hectares, is much narrower. It permits the extension or alteration of an existing agricultural building and certain works, within its own cumulative ground area limit, but it does not permit a new building. That distinction is the single most common misunderstanding on smallholdings.

Both classes are cumulative and both count earlier development. A unit that has already used its allowance on a previous building has no allowance left, and the council will check the planning history before it checks the drawings.

What reasonably necessary means

The test is whether the building or operation is reasonably necessary for the purposes of agriculture within the unit as it exists. It is not whether the building would be useful, nor whether the farmer wants it.

Councils look at the scale and nature of the enterprise: the stock numbers, the cropping, the storage requirement in tonnes or bales, the machinery to be housed, and whether existing buildings on the unit could accommodate the need. A 1,000 m2 shed on a 6 hectare unit running twenty sheep will not pass, and the council can say so.

Evidence that helps includes a stocking or cropping schedule, a calculation of the storage volume needed, a schedule of existing buildings with their current use and spare capacity, and a short statement of the enterprise and its trajectory. Put it in writing with the notification rather than waiting to be asked.

Two further points. The building must be used for agriculture, and using a Part 6 building for storage of non-agricultural goods, a contracting business or general commercial storage is a breach of the condition attached to the class. And the rights fall away where the land was brought into agricultural use only recently, since the Order requires the unit to have been in agricultural use for a period before certain rights apply. This is exactly the kind of detail that separates Part 6 from the general run of permitted development rights.

Prior notification and the 28 day route

Part 6 development is not a free-for-all. For most buildings, and for private ways, the farmer must first apply to the council for a determination as to whether its prior approval will be required.

The matters differ by development type. For a building, the council may require approval of the siting, design and external appearance. For a private way, the siting and means of construction. For an excavation or a deposit of waste, the siting.

The sequence runs like this.

1. Submit the prior notification with a description of the development, a plan of the site, and the fee.
2. The council has 28 days to notify you either that prior approval is not required, or that it is.
3. Where prior approval is not required, or the council fails to respond within the period, you may proceed in accordance with the details submitted.
4. Where prior approval is required, you submit the details and the council determines them.

Miss a step and the development is unlawful even if it would otherwise have been permitted. Starting before the 28 days have run, or building something materially different from what was notified, are the two ways this goes wrong.

The council can also require the building to be removed and the land restored where the unit ceases to be used for agriculture within a defined period after the building is completed. That condition survives a change of ownership.

Design, siting and external appearance

Where prior approval is required, the council's control is narrow but real. It cannot refuse the principle of an agricultural building on a qualifying unit. It can direct where the building sits and what it looks like.

Officers concentrate on a short list: whether the building can be grouped with the existing farmstead rather than placed in an open field, whether the ridge height and roof pitch match the existing buildings, whether the cladding colour is a recessive dark green, grey or brown rather than a bright profile sheet, whether the access track is visible from a public road or a footpath, and whether landscape planting can soften the edge.

Answering those points in the notification usually produces a determination that prior approval is not required, which saves several weeks. A one-page siting and design note with a photograph of the existing farmstead, a colour reference and a landscape proposal is enough.

Where the site is in a National Park, a National Landscape or a conservation area, expect a fuller assessment and check whether the rights are restricted at all on that land.

Where hobby farming falls outside Part 6

The most common disappointment is the smallholding under 0.4 hectares, or the paddock used for horses, where the owner assumes farm rights apply.

If the unit is below 0.4 hectares, there are no Part 6 rights and a full planning application is needed for any building. If the use is equestrian rather than agricultural, the same is true regardless of acreage. If the land was recently taken out of a larger holding, the unit may not qualify.

In those cases the route is a planning application, assessed against countryside policy in the adopted local plan. Field shelters, stables, hay barns and menages are all decided on landscape impact, access, drainage and the effect on neighbours, and a short Planning Statement setting out the need, the alternatives considered and the design response does more than the drawings alone.

It is also worth confirming whether what you propose is development at all. Some structures are not, and the question of what counts as development under section 55 is often the least expensive one to answer first.

Browse the report types a rural application is likely to need on PlanScope before you notify the council.

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.