Holdings under five hectares and what Part 6 allows

Five hectares is the line that decides what you can build without a planning application. Part 6 of Schedule 2 to the General Permitted Development Order 2015 splits agricultural permitted development in two: Class A covers agricultural units of five hectares or more, and Class B covers units of at least 0.4 hectares but less than five. Under part 6 class B small holding rights you can extend and alter what is already there, form tracks and hard surfaces, and install plant. You cannot put up a new building at all.

That single omission is why so many smallholders discover, late, that the barn they costed needs a full application.

Where the five hectare line falls

The unit is measured as an agricultural unit, meaning land occupied as a unit for agricultural purposes. It is the occupation that counts, not the title. Land you rent in counts if you occupy it as part of the same farming operation, and land you let out to someone else does not.

Below 0.4 hectares there are no Part 6 rights at all. Between 0.4 and five hectares you have Class B. At five hectares and above you move to Class A, with its new building rights subject to the 465 square metre ground area limit and the other conditions in A.1.

The measurement is taken at the time of the development. A holding that was six hectares two years ago but has since sold a field is a Class B unit now.

What Class B permits

Class B allows six categories of operation on a qualifying unit, each reasonably necessary for the purposes of agriculture within that unit.

• Extension or alteration of an existing agricultural building.
• Installation of additional or replacement plant or machinery.
• Provision, rearrangement or replacement of a private way.
• Provision or replacement of a hard surface.
• Deposit of waste material arising from building or engineering operations.
• Certain operations connected with fish farming.

Read the first one carefully. It is extension or alteration, which presupposes a building to extend. There is no right to erect a new building, no right to put up a dwelling, and no right to erect a building for a non-agricultural purpose however small.

So the practical sequence on a smallholding is to establish what buildings you lawfully have, then work out what can be done to them. An owner with no buildings has no Class B building rights worth having.

The limits on an extension

Class B also caps the proportionate increase in the size of the original building, and the cap is tight. Measure the original cubic content before anyone draws anything, and read the current wording of B.1 and B.2 on legislation.gov.uk rather than working from a figure in an old note, because Part 6 has been amended several times.

Two conditions catch people out after the event. The building has to be used for agriculture on that unit, so a barn extended under Class B and then let for storage to an unconnected business is in breach. And if the agricultural use stops within ten years of the works being completed, the authority can require removal where no subsequent permission has been obtained.

Units split by ownership or tenancy

The common difficulty is the holding that looks like one farm and is legally three. Owner-occupied fields, a grazing licence over a neighbour's paddock and a tenancy of a block down the lane can add up to seven hectares on a map and still not be a single agricultural unit.

Ask three questions. Is the land occupied by the same person or entity. Is it farmed as one operation, with shared labour, machinery and stock. Is the occupation of each parcel on terms that give real control, rather than a bare licence for seasonal grazing.

Where the answers diverge, the safe assumption is the smaller unit. A prior notification submitted on the basis of a unit the council does not accept is worse than a full application, because you have now told the authority what you intend and the clock gives you nothing.

Evidencing the extent of the unit

Councils ask for this more than they used to, and the evidence is straightforward to assemble.

1. A plan of the whole unit with every parcel outlined and its area stated in hectares.
2. Title documents or tenancy agreements for each parcel, with the term and the permitted use.
3. The holding number and the current land parcel information for the holding.
4. A short description of the farming enterprise: stock numbers, cropping, machinery kept.
5. An explanation of why the proposed works are reasonably necessary for that enterprise, with figures.

Point five is the one that fails. "The building is needed for storage" tells an officer nothing. "The holding keeps 40 ewes and cuts 180 bales a year, and the existing building takes 60 bales" is an argument. Where the land is good quality and the works affect it, an Agricultural Land Classification survey may also be requested, particularly on sites where best and most versatile land is in play.

The prior notification procedure

Part 6 development of certain kinds requires an application to the authority for a determination as to whether its prior approval will be required for the siting, design and external appearance of the building or the route and width of a private way. The authority has 28 days to tell you whether approval is required. If it says nothing in that period you may proceed in accordance with the details submitted.

Three practical points. Submit accurate details, because what you may build is what you notified. Do not start work before the period expires, since early works are unauthorised even if the notification would have succeeded. And expect the authority to use the design limb properly on prominent sites: a grey profile sheet building on a ridge in a National Landscape will attract a requirement for approval and then a request for a Landscape and Visual Impact Assessment.

When a full application is the only route

Four situations put you outside Part 6 entirely, and recognising them early saves a wasted fee.

A new building on a unit under five hectares. Any dwelling. Any building for a use that is not agriculture, including equestrian use, since keeping horses is not agriculture and the position on livery yards and the point horses become a business is a separate question. And any diversification into workshops, offices, storage for third parties or visitor use, where the route is a planning application and the policy support for farm diversification into workshops and offices is what you build the case on.

For those applications a Planning Statement that explains the enterprise, the functional need and the siting choice does most of the work. And on a small holding the siting argument matters more than the design: officers accept plain agricultural buildings in sensible places far more readily than well-detailed ones in the middle of a field.

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 is the only formal way to confirm that works are lawful. PlanScope produces AI-assisted draft reports for planning applications, and reports should be reviewed before submission. PlanScope does not guarantee planning approval.