GUIDE · FOR UK SOLAR INSTALLERS · 13 MIN READ

Commercial Solar Planning Permission and Permitted Development

Most a panel can stand proud of a pitched roof

0.2m

Most a panel can stand proud of a pitched roof

Height limit above a flat roof, and gap from every roof edge

1m

Height limit above a flat roof, and gap from every roof edge

Above this, rooftop solar needs prior approval

50kW

Above this, rooftop solar needs prior approval

The 1MW limit was removed on 21 Dec 2023

No cap

The 1MW limit was removed on 21 Dec 2023

Planning comes up on almost every commercial survey, usually as "do we need permission?". The honest answer is "probably not, but here is what decides it", and the rules changed at the end of 2023, so older advice about a 1MW limit is out of date. This guide covers non-domestic buildings only: offices, warehouses, factories, farms, schools and the like.

Last updated 22 October 2026. The England rules are taken from the revised text of the General Permitted Development Order 2015 on legislation.gov.uk, read that day, which showed no outstanding changes to Class J. Paragraph numbers are given so you can check them. This is a guide, not planning advice for a particular site: the council decides.

Class J: what it allows

Class J grants permitted development for the installation, alteration or replacement of:

• (a) microgeneration solar thermal equipment on a building;
• (b) microgeneration solar PV equipment on a building; or
• (c) other solar PV equipment on the roof of a building,

on a building other than a dwellinghouse or a block of flats. "Microgeneration" takes its meaning from section 82 of the Energy Act 2004, which caps electricity generation at 50kW. So in practice: up to 50kW, panels can go on a roof or a wall under Class J(a) or (b); above 50kW, Class J(c) covers the roof only, and comes with the prior approval step below.

The limits

Break any of these and the job is outside Class J and needs a planning application:

Two conditions apply to every Class J installation (J.4(1)): 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 it must be removed as soon as reasonably practicable when no longer needed.

Prior approval over 50kW

For Class J(c), rooftop PV that isn't microgeneration, the developer must, before starting, apply to the local planning authority for a determination as to whether its prior approval is required for the design or external appearance of the development, in particular the impact of glare on occupiers of neighbouring land (J.4(2)). The process, from J.4(3) to J.4(12):

1. Send a written description of the development, a plan showing the site and the proposal, the developer's contact address, an email address if you want to be contacted that way, and any fee.
2. The council gives notice by a site notice for at least 21 days (public holidays not counted), or by serving notice on adjoining owners or occupiers. It can ask for further information it reasonably needs.
3. It takes any representations into account and has regard to the National Planning Policy Framework, so far as relevant to the matters for prior approval.
4. Work may start only when the council says prior approval isn't required, gives prior approval, or 56 days pass from receipt of the application without the council notifying a decision.
5. Build it as approved, or as described in the application. The council may attach conditions related to the matters it was considering, and may refuse an application that doesn't comply with Class J or lacks the information to show that it does.

Check the council's current fee when you apply. On a proposal, build the 56 days into the programme, alongside the DNO connection: our G99 application guide covers that side.

What changed in 2023

The Town and Country Planning (General Permitted Development etc.) (England) (Amendment) (No. 2) Order 2023, SI 2023/1279, came into force on 21 December 2023. For non-domestic solar it:

• Removed the 1MW cap. Class J(c) used to exclude rooftop PV over 1MW. The government's explanatory memorandum says the change means there is no limit on the electricity generated by rooftop solar on non-domestic buildings.
• Opened up roof slopes facing the road in protected areas. Before, Class J excluded a roof slope fronting a highway on article 2(3) land. That exclusion has gone. The memorandum says a matching proposal for walls fronting a highway was not brought forward, so that exclusion (J.2(c)) stays.
• Added Class OA for solar canopies over non-domestic off-street parking, with prior approval. See our solar carports guide.
• Changed Class K for stand-alone solar within the curtilage of non-domestic buildings on article 2(3) land (below).

The only change to Class J since then, by SI 2026/313 on 9 April 2026, trimmed some wording in the prior approval paragraph (J.4(8)(b)). Changes to plug-in and domestic solar later in 2026 were to the domestic classes, not Class J.

Flat and pitched roofs

On a pitched roof, the test is 0.2m beyond the plane of the roof slope, measured perpendicular to the roof's external surface (J.1(a)). Check the full build-up, especially on older roofs where you are adding battens, spacers or over-cladding.

On a flat roof the highest part of the solar equipment must be no more than 1m above the highest part of the roof, chimneys excluded (J.1(b)). The tilt you choose for the frames, and the length of the module, decide whether you are inside it. On both, keep every panel at least 1m from the external edge of the roof (J.1(c)). That edge zone also matters for access and wind loads, and the insurers' code RC62 asks for clear access routes for maintenance and firefighting; see our RC62 guide.

Conservation areas and article 2(3) land

"Article 2(3) land" is land within a conservation area, an area of outstanding natural beauty, an area specified for section 41(3) of the Wildlife and Countryside Act 1981, the Broads, a National Park or a World Heritage Site. On that land:

• Rooftop solar on a non-domestic building is permitted under Class J within the normal limits, including on a roof slope facing the road (since 21 December 2023).
• Wall-mounted solar is not permitted on a wall that fronts a highway (J.2(c)).
• The general condition to site equipment to minimise its effect on the building's appearance and the area's amenity still applies, and above 50kW the council looks at design and appearance through prior approval.

Councils can also use article 4 directions to withdraw permitted development rights across a defined area, so always ask the council whether one applies.

Listed buildings

Class J does not apply to a listed building, a building within the curtilage of a listed building, or a site designated as a scheduled monument (J.1(e), (f)). That means a planning application. On top of that, section 7 of the Planning (Listed Buildings and Conservation Areas) Act 1990 says no one may carry out works to alter a listed building in any way that would affect its character as a building of special architectural or historic interest unless the works are authorised, which in practice means listed building consent. Check the curtilage question early: farm buildings and outbuildings near a listed farmhouse are a common catch.

Ground-mounted arrays and carports

Permitted development for ground-mounted solar at non-domestic premises is narrow. Class K allows one stand-alone solar installation within the curtilage of a building other than a house or flats, and only if (K.1):

• it is no more than 4m high (2m on article 2(3) land where it is nearer the road than the building, which then needs prior approval on appearance);
• it is at least 5m from the boundary of the curtilage;
• the panels total no more than 9 square metres, and no dimension of the array (including any housing) exceeds 3m;
• it is not within the curtilage of a listed building or on a scheduled monument.

That is a single small array, so a commercial ground-mount usually needs a planning application. Solar canopies over a car park are a different class, Class OA, with their own limits; they are covered in our solar carports guide.

When permitted development doesn't apply

The government's planning practice guidance sets out two ways permitted development rights can be removed: an article 4 direction, which withdraws specified rights across a defined area, and a condition on a planning permission. Either means a planning application, so ask the customer for the building's planning history and check with the council.

Where it isn't clear whether a project is permitted development, the same guidance says you can apply for a certificate of lawful development, which gives a legally binding decision from the council. On a large roof or a sensitive site it is cheap insurance for the customer before they sign.

Building regulations and structure

Permitted development is about planning. Building regulations are separate, and the Planning Portal says that if you install solar on a roof, building regulations will normally apply: the roof's ability to carry the load must be checked and proven, some strengthening work may be needed, and the regulations also apply to other parts of the work such as the electrical installation.

• Self-certification. In England, Schedule 3 to the Building Regulations 2010 lets a person registered with an authorised competent person scheme self-certify the installation in a building of a system to produce electricity by microgeneration or from renewable sources. If you aren't registered for that type of work, or the job goes beyond it (structural strengthening, say), involve building control before you start.
• Structure. Older commercial roofs are where the structural question bites: fragile sheeting, asbestos cement, light purlins. Our asbestos roof guide covers what to check, and RC62 recommends a structural survey by a competent person before installation.

Wales, Scotland and Northern Ireland

Class J is part of the England order. The other nations have their own, with different limits:

• Wales. The Welsh Government's guidance says many non-domestic installations are likely to be permitted development, with limits including 200mm from the roof or wall, 1m above a flat roof and 1m from the roof edge, and says planning consent is needed for panels in a conservation area or World Heritage Site on elevations visible from the highway.
• Scotland. Planning Circular 2/2024 (28 May 2024) explains Class 6J (panels on non-domestic buildings) and Class 6N (free-standing panels in the curtilage). Under Class 6J panels may protrude no more than 1m from the building's surface, and there are exclusions for listed buildings, World Heritage Sites and sites within 3km of an aerodrome, among others.
• Northern Ireland has its own permitted development order. Check with the council before relying on any of the England rules.

Survey checklist

Settle the planning position at the first visit, before the design fills the roof:

1. 1Confirm the nation and the building type. Class J is England only, and only for buildings that are not a dwellinghouse or a block of flats. A mixed-use building or a block of flats needs a closer look.
2. 2Ask whether the building is listed or in a conservation area. A listed building, or one within its curtilage, is outside Class J. Conservation areas, National Parks, AONBs, the Broads and World Heritage Sites are article 2(3) land, where walls fronting a highway are excluded.
3. 3Ask whether permitted development rights have been removed. An article 4 direction or a condition on an earlier planning permission can take them away. The customer or the council will know; a lawful development certificate settles any doubt.
4. 4Measure the roof against the limits. 0.2m on a pitched roof, 1m above a flat roof, 1m back from every edge. On a flat roof, the tilt of the frames decides the height.
5. 5Work out whether it is microgeneration. Up to 50kW on the roof is Class J(a) or (b) with no prior approval. Over 50kW is Class J(c): apply for prior approval and allow up to 56 days before you start.
6. 6Check the structure. The roof has to be shown to carry the load. Get it assessed by a competent person before the proposal, not after it is signed.
7. 7Plan building control and the grid together. Decide who handles building regulations, and start the DNO application in parallel with planning rather than after it.

The rest of the visit is in our commercial solar survey checklist. If you're short of surveys to do, our commercial solar leads are booked appointments with business owners.

Commercial solar planning permission: FAQ