Which rule applies: a farm building is not a house
The permitted-development rights for solar sit in Part 14 of Schedule 2 to the General Permitted Development Order 2015. Class A covers a dwellinghouse; Classes J and K cover buildings and land that are not dwellings — which is every barn, shed, parlour, store and glasshouse on a working farm. A surprising number of guides, including some written for farmers, quote the householder rules or the pre-2023 limits. The figures below are from Classes J and K as they stand after the amendment that took effect in December 2023.
Roof-mounted arrays: Class J
Class J permits the installation, alteration or replacement of solar PV or solar thermal equipment on a building other than a dwellinghouse or a block of flats. The conditions that matter on a farm roof:
- Projection. On a pitched roof the panels must not project more than 0.2 m beyond the plane of the roof slope; on a flat roof, no more than 1 m above the plane of the roof. Low-profile rails on a portal-frame roof sit well inside this; tilt frames on a flat roof need checking.
- Edge setback. No part of the equipment may be within 1 m of the external edge of the roof.
- Listed buildings and scheduled monuments. Class J does not apply on a scheduled monument, on a listed building, or within the curtilage of a listed building. That last point catches modern sheds standing in the yard of a listed farmhouse.
- Article 2(3) land. In a conservation area, National Park, National Landscape or World Heritage Site, the panels must not be on a wall or roof slope that fronts a highway.
- Capacity. There is no capacity cap. The former 1 MW limit was removed by S.I. 2023/1279.
- Prior approval above 50 kW. Where the installed capacity exceeds 50 kW, the developer must apply to the council for a determination as to whether its prior approval is required for the design and external appearance of the equipment, in particular the impact of glare on occupiers of neighbouring land. The council has 56 days; if it does not respond in time, the development can proceed.
- General conditions. The equipment must, so far as practicable, be sited to minimise its effect on the external appearance of the building and the amenity of the area, and be removed as soon as reasonably practicable when no longer needed.
For a typical livestock or grain building — profiled steel or fibre cement, 10–15° pitch, no listing, panels flush on rails — the whole array is permitted development, and the only planning step for an array above 50 kW is the prior-approval application. Below 50 kW there is no planning step at all.
Stand-alone arrays: Class K, and why it rarely helps a farm
Class K permits stand-alone solar equipment within the curtilage of a non-domestic building, but its limits are set for a car-park canopy or a small ground frame, not a field array:
- Only one stand-alone installation within the curtilage.
- No part higher than 4 m above ground.
- Not within 5 m of the boundary of the curtilage.
- Panel surface area no more than 9 m², and no dimension of the array over 3 m.
- Not within the curtilage of a listed building, and not on a scheduled monument.
- On article 2(3) land, not nearer to a highway than the building.
A yard or field array at any useful scale therefore needs a planning application. The agricultural permitted-development rights in Part 6 do not rescue it: Part 6 Class A covers buildings and works “reasonably necessary for the purposes of agriculture” on units of 5 ha or more, up to 1,500 m² and subject to prior notification, and solar generation is not mentioned. Ground-mounted PV on farmland is a planning application in England, full stop, and the size of that application is what determines whether it is decided locally or as nationally significant infrastructure.
Listed barns, conservation areas and Article 4 directions
A listed building takes the roof out of Class J entirely. The works need Listed Building Consent and the installation needs planning permission, and the council will assess harm to the building’s significance. Two things help. The National Planning Policy Framework republished on 17 August 2026 says in policy CC2 that substantial weight should be given to the benefits of renewable energy on existing buildings where permitted development does not already apply, and in policy HE6 that harm to a designated heritage asset should be weighed against public benefits, which expressly include enabling energy-efficiency and low-carbon measures. A scheme on a rear slope of a later agricultural range, with a heritage statement and pre-application advice, is a very different proposition from panels on the principal elevation of a tithe barn.
In a conservation area or National Park the Class J right still applies except to a wall or roof slope fronting a highway. Some councils go further and remove permitted development rights for solar with an Article 4 direction; the council’s published list of directions is the place to check, and a Lawful Development Certificate is the way to remove doubt before you spend money.
Scotland, Wales and Northern Ireland
The English order does not apply elsewhere. In Scotland, rooftop solar on non-domestic buildings has its own permitted-development class (Class 6J) with its own limits and exclusions for listed buildings and conservation areas. Wales and Northern Ireland each have their own general permitted development orders; check the current text or the planning authority’s guidance rather than reading across from the English limits above. The grid rules, by contrast, are the same everywhere: any array above 3.68 kW per phase needs a G99 application approved by the distribution network operator before it is energised, and that approval is usually the real critical path.
What the top-ranking guides still get wrong
| Claim | Position in the order (checked September 2026) |
|---|---|
| “Farm-roof solar is permitted development up to 1 MW.” | The 1 MW cap was removed in December 2023. Above 50 kW the condition is prior approval on design and glare, not a cap. |
| “Panels may project up to 200 mm.” | The current text says 0.2 m on a pitched roof and 1 m on a flat roof — the same distance for pitched roofs, but the flat-roof allowance is often omitted. |
| “Agricultural permitted development (Part 6) covers solar.” | Part 6 covers agricultural buildings and works; solar is dealt with in Part 14 Classes J and K. |
| “Ground-mount up to 9 m × 9 m × 4 m is permitted.” | Class K allows one stand-alone installation of no more than 9 m² panel area, no dimension over 3 m, no higher than 4 m — not a 9 m by 9 m array. |
| “A modern shed next to a listed farmhouse is fine.” | Class J excludes any building within the curtilage of a listed building. |
A five-minute check before you get quotes
- Is the building, or any building whose curtilage it stands in, listed? If yes, plan for Listed Building Consent and a planning application.
- Is the site in a conservation area, National Park, National Landscape or World Heritage Site? If yes, keep panels off highway-facing slopes and check for an Article 4 direction.
- Will the array exceed 50 kW? If yes, budget 56 days for the prior-approval determination and get the glare assessment into the design.
- Will the panels sit within 0.2 m of the roof plane and at least 1 m from every edge? Ask the installer to show this on the layout drawing.
- Is any part of it ground-mounted at working scale? If yes, it is a planning application.
Installers who work on farm buildings answer all five before quoting. For how to check the rest of what they tell you, see agricultural solar panel installers; for the wider rules and cost picture, solar panels for agricultural buildings; and for the head-term guide, solar panels for farm buildings. If the roof is asbestos cement, the planning question is the easy one — the roof decision is on solar panels on asbestos cement farm roofs.
Planning questions farms ask
Do I need planning permission for solar panels on a farm building?
In England, usually not. Solar on the roof of a non-domestic building is permitted development under Part 14 Class J of the General Permitted Development Order if the panels project no more than 0.2 m beyond the plane of a pitched roof (1 m above a flat roof), sit at least 1 m from the external edge of the roof, and the building is not listed, within the curtilage of a listed building, or a scheduled monument. Above 50 kW you must apply for prior approval on design, external appearance and glare before starting.
Is there a size limit for permitted development solar on a barn?
Not a capacity limit any more. The 1 MW cap in Class J was removed by the December 2023 amendment (S.I. 2023/1279). What remains is the prior-approval condition above 50 kW: the council has 56 days to decide whether it wants to control the design and the impact of glare on neighbours. Below 50 kW, no application of any kind is needed if the physical limits are met.
What about a ground-mounted array in the farmyard?
Class K covers stand-alone solar on non-domestic land but only at garden scale: one installation per curtilage, no more than 4 m high, at least 5 m from the boundary, with a panel area of no more than 9 m² and no dimension over 3 m, and not within the curtilage of a listed building or on a scheduled monument. Anything a working farm would actually build needs a planning application.
Can I put solar on a listed barn?
Not under permitted development — Class J excludes listed buildings and anything within their curtilage. You need Listed Building Consent for the works, and planning permission for the installation. The National Planning Policy Framework as republished in August 2026 (policy HE6) asks the council to weigh harm to the building’s significance against public benefits, which expressly include enabling energy efficiency and low-carbon measures, so a well-designed scheme is not hopeless, but the consent is not a formality either.
Does a conservation area or National Park change the rules?
Yes. On article 2(3) land — conservation areas, National Parks, National Landscapes (the former AONBs) and World Heritage Sites — Class J does not permit panels on a wall or roof slope that fronts a highway. A rear or field-facing roof slope still qualifies. Some councils also remove permitted development rights with an Article 4 direction, so check the council’s list before assuming the class applies.
Should I get a Lawful Development Certificate?
For a large array, a certificate is cheap insurance. It is the council’s written confirmation that the development is lawful under permitted development, which lenders, landlords and future buyers can rely on. The NFU’s planning note recommends one, and on a tenanted holding the landlord will often want it.