Part 6 Class B: agricultural holdings under 5 hectares

On a holding of between 0.4 and 5 hectares you cannot put up a new agricultural building under permitted development. Class B of Part 6 of Schedule 2 to the General Permitted Development Order 2015 covers extensions and alterations to existing agricultural buildings, plant and machinery, private ways, hard surfaces, services and waste deposits, and it stops short of a new building. That single omission is the difference between Class B and the Class A rights that apply at 5 hectares and above, and it catches smallholders every year.

Below 0.4 hectares there are no Part 6 rights at all. A two acre paddock with a field shelter is on its own.

What Class B permits on a smaller unit

The right applies to agricultural land in an agricultural unit of not less than 0.4 hectare and less than 5 hectares, and every item has to be reasonably necessary for the purposes of agriculture within that unit.

What falls inside:

• Extension or alteration of an existing agricultural building.
• Installation of additional or replacement plant or machinery.
• Provision, rearrangement or replacement of a sewer, main, pipe, cable or other apparatus.
• Provision, rearrangement or replacement of a private way.
• Provision of a hard surface.
• Deposit of waste.
• Certain operations in connection with fish farming.

What falls outside: the erection of any new building, and any dwelling, extended or altered or new.

The practical consequence is that a smallholding with no existing agricultural building has almost nothing to extend. Owners sometimes argue that a shipping container or a field shelter counts as a building to be extended, and authorities resist that, particularly where the structure itself was never lawfully authorised.

The 0.4 hectare lower limit

Two thresholds operate, and they are easy to confuse.

The unit as a whole must be at least 0.4 hectare. And the development must not be carried out on a separate parcel of land of less than 0.4 hectare forming part of that unit. A holding of 3 hectares in one block passes both. A holding of 3 hectares made up of a 2.8 hectare field and a 0.2 hectare paddock across the road cannot use the right on the small paddock.

Measure the agricultural unit, not the registered title. The unit is the land occupied as a unit for agricultural purposes, which can span several titles and can exclude land let out separately. Where the figure is close to 0.4 hectare, get it measured properly from the title plans and a site survey rather than estimated from mapping.

Occupation also has to be agricultural in fact. Land used for grazing horses kept for recreation is not in agricultural use, and a holding whose only activity is keeping a few hens for the household will struggle to show that anything is reasonably necessary for agriculture.

What is excluded compared with Class A

Both classes share the same protective limits. No part within 25 metres of a metalled trunk or classified road. No livestock building, or slurry or sewage sludge storage, within 400 metres of the curtilage of a protected building. A ground area ceiling of 1,000 m² for the building as extended. Height restricted generally, and more tightly within 3 kilometres of an aerodrome perimeter.

Read the current text of the Part before relying on any of these. The Order has been amended repeatedly and the limits are set out with qualifications that a summary cannot carry.

Extensions and alterations to existing buildings

This is the main use of Class B, and the limit that bites hardest is appearance.

The right does not extend to development that would materially affect the external appearance of the premises. A lean-to along one side in matching profile sheeting, replacing cladding like for like, or raising an eaves height slightly will usually pass. Changing a building's roof profile, adding a different cladding system across a visible elevation, or forming large new openings in a frontage probably will not.

Cumulative area matters too. The ground area of the building as extended must stay within the ceiling, and that is measured for the building as a whole rather than for the extension alone.

Significant extensions and alterations trigger the prior notification procedure, so an application for a determination as to whether the authority's prior approval is required must be made before work starts, with a description of the development, a plan and the current fee. Work must not begin until the authority responds or the stated period has expired.

The honest advice on a marginal case is to notify. The cost of notifying is a fee and a short wait. The cost of being wrong is an enforcement notice and the removal of the works.

Hard surfaces and tracks

Hard surfaces and private ways are where Class B earns its keep on a small holding, because a yard apron or an access track transforms how the land works in winter.

The planning points are drainage and the highway. A new impermeable surface changes surface water run-off, and a track that discharges silty water onto a public road creates a highway problem the authority will take seriously. Design for infiltration where the ground allows, use permeable construction where it does not, and intercept run-off before the gate. The same thinking applies to domestic surfacing, as front garden paving and permeable surfaces explains in a different context.

A new or altered private way triggers prior notification of siting and means of construction. A new access onto the public highway is a separate matter requiring its own consents, and the 25 metre rule applies to development near trunk and classified roads.

Depositing waste on the holding is permitted within limits where reasonably necessary for agriculture, and importing material from elsewhere is not what the right is for. Waste deposits also engage environmental permitting and exemption rules, which sit outside the planning system entirely.

Equestrian use and why it falls outside

Keeping, breeding, training or exercising horses is not agriculture in planning terms. Grazing horses as livestock can be agricultural, and the line turns on what actually happens on the land.

That distinction has three consequences on a smallholding. A stable block needs full planning permission. A menage or an arena needs full planning permission and usually raises drainage, lighting and landscape issues. And a change from grazing to equestrian use can itself be a material change of use requiring permission, even with no new building.

Mixed holdings are common and messy. Where a few acres are grazed by sheep and a paddock is used for a horse, keep records of each activity so the agricultural case for any Class B development can be made on the agricultural part.

Where a full application is needed

Expect to apply in each of these situations.

1. Any new agricultural building, of any size, on a unit under 5 hectares.
2. Any dwelling, including a worker's dwelling, which needs a functional need case and usually an occupancy condition.
3. Any equestrian building or use.
4. Extensions or alterations that would materially affect the external appearance of the premises.
5. Development within 25 metres of a metalled trunk or classified road, or livestock and slurry structures within 400 metres of a protected building.
6. Any diversification use, from holiday lets to farm shops, which is not agriculture.

For those applications a short Planning Statement setting out the holding, the agricultural activity, the need for the building and why the siting is the least harmful option does most of the work. Where an existing building might later be converted to a dwelling, the agricultural use history becomes the asset, and the evidential standard is the one described in proving a building was in agricultural use for Class Q. The limits on what conversion works are permitted are set out in Class Q structural works and what is reasonably necessary.

A lawful development certificate is the only formal way to confirm that works already carried out are lawful. On a small holding with a patchy history, it is often money well spent before a sale.

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.

Enter the holding's postcode on PlanScope to see which documents a farm application is likely to need.