Part 6 Class A: farm buildings on 5 hectares or more

On an agricultural unit of 5 hectares or more, Class A of Part 6 of Schedule 2 to the General Permitted Development Order 2015 allows you to put up a farm building without a planning application, provided it is reasonably necessary for agriculture on that unit and stays inside the limits. For most buildings you still have to serve a prior notification on the council and wait 28 days, because the authority can require its approval of siting, design and external appearance.

The rights are generous and narrow at the same time. Generous because a 1,000 m² steel portal frame is a lot of building to get without an application. Narrow because a single detail, a classified road 20 metres away or a neighbour's cottage 380 metres from a livestock shed, takes the whole proposal outside.

The agricultural unit test

Class A applies to an agricultural unit of 5 hectares or more. The unit is the land occupied as a unit for agricultural purposes, which is not the same as the land in one title, and not the same as a field parcel.

Three points decide most arguments.

The development has to be reasonably necessary for the purposes of agriculture within that unit. A building to store a neighbour's hay, to house a contracting business, or to serve an equestrian enterprise is not agricultural development, and equestrian use in particular sits outside agriculture in planning terms except where horses are grazed as livestock.

The development cannot be on a separate parcel of land of less than 1 hectare forming part of the unit. An isolated half-hectare paddock across the lane does not carry the right, even if the whole holding is 40 hectares.

And occupation matters. A tenant occupying the unit can use the right. A landowner who has let the whole holding out and occupies none of it is in a weaker position, because the right attaches to agricultural use of the unit rather than to ownership.

Floor area and height limits

The cumulative floor area rule catches people. If you built a 600 m² shed 18 months ago and want another 500 m² within 90 metres of it, the combined figure breaches the cap and the second building needs a full application.

A protected building is broadly a permanent building normally occupied by people, excluding buildings on the same agricultural unit and buildings occupied by someone employed in agriculture on that unit. Measure the 400 metres from the curtilage rather than from the wall, and measure it to the nearest part of the proposed structure or excavation.

Prior notification of siting, design and materials

Part 6 does not simply grant the building. For a significant extension or alteration of a building, the formation or alteration of a private way, excavations or waste deposits over 0.5 hectare, or the placing of a tank in waters, you must apply to the authority for a determination as to whether its prior approval is required for the siting, design and external appearance of what is proposed.

The application needs a written description of the development, a plan showing the site, and the fee set by the current fee regulations. Check the figure against the published schedule, because planning fees are indexed.

That threshold is met where the cubic content of the original building would be exceeded by more than 10 per cent, or where the height of the original would be exceeded. Small repairs and modest additions fall outside the notification requirement, and the honest advice is to notify anyway where the margin is close, because the cost of being wrong is an enforcement notice.

The 28 day period and what the authority may control

You must not begin development before one of three things happens: the authority tells you in writing that prior approval is not required, the authority gives its approval, or 28 days pass from the day the authority received the application without it responding.

The 28 day period runs from receipt, not from validation, and a weekend or bank holiday does not extend it. Diary the date.

What the authority can control is limited to siting, design and external appearance. It cannot refuse the principle of an agricultural building that otherwise meets the limits, and it cannot use the notification to reopen questions about the need for the building, though it can and does ask whether the proposal is agricultural at all. Where a site is prominent in a National Landscape or a National Park, expect close attention to materials, colour and the position against existing buildings, and consider commissioning a Landscape and Visual Impact Assessment where the siting is exposed.

Where approval is given, the development has to be carried out in accordance with the approved details and begun within five years of the approval.

Distance from a protected building

The 400 metre rule for livestock and slurry is the limit that most often forces a full application, and it is worth testing early with a measured plan rather than an estimate.

Two refinements help. A building initially erected for machinery storage is not caught, and later changing it to livestock accommodation would be a different matter requiring its own consideration. And a cottage sold off the holding years ago becomes a protected building once it is no longer occupied by someone employed in agriculture on the unit, which is how farms lose rights they thought they had.

Where you are inside 400 metres, a full planning application is the route, and the case then turns on odour, noise and amenity rather than on the Order.

Dwellings, roads and excavations

No dwelling can be erected, extended or altered under Class A. A worker's dwelling on a farm needs a full application, with a functional need case and usually an occupancy condition.

Private ways get their own treatment. Forming or altering a farm track triggers the prior notification requirement for siting and means of construction, which in practice means the route, the surfacing, and how it meets the public highway. A new or widened access onto a classified road needs separate highway consents, and the 25 metre rule bites on buildings close to such roads.

Excavations and engineering operations are permitted where reasonably necessary for agriculture, with notification required above 0.5 hectare for excavations or waste deposits. Importing waste material from off the unit is not what the right is for, and the environmental permitting regime applies separately to deposits of waste.

Where development falls within the environmental impact assessment regime, permitted development rights do not apply and screening comes first.

Record keeping for the unit

Farms carry permitted development history for decades, and the paperwork is what protects it.

1. Keep a plan of the unit with every building dated and its ground area recorded, so the cumulative 1,000 m² test can be run in minutes.
2. Keep each prior notification application, the plan submitted and the authority's written response or the evidence that 28 days expired.
3. Record the agricultural justification for each building at the time, because explaining it ten years later is harder.
4. Note the 10 year removal obligation. Where the agricultural use of a building, structure, private way or excavation permanently ceases within 10 years of substantial completion and no permission has been granted, it must be removed and the land restored.
5. Where a building's future lawfulness matters, for example before a sale or a Class Q conversion, apply for a certificate of lawfulness. A lawful development certificate is the only formal way to confirm that works are lawful, and the evidential standard is the same one that applies to proving a building was in agricultural use for Class Q.

Agricultural buildings converted later run into the limits on what counts as reasonably necessary building work, which is set out in Class Q structural works and what is reasonably necessary. Where a full application is needed instead, a short Planning Statement setting out the agricultural need and the siting logic does most of the work.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it, and read the current text of Part 6 for the limits that apply to your land.