Solar panels and the 200 millimetre projection limit
Class A of Part 14 allows domestic solar without permission, subject to a 0.2 metre projection limit that tilted frames on flat roofs almost always exceed.
Solar panels are permitted development on most houses in England under Class A of Part 14 of Schedule 2 to the General Permitted Development Order 2015, and the condition that decides most awkward cases is the projection limit. The equipment must not protrude more than 0.2 metres, measured perpendicularly, beyond the plane of the roof slope or the wall it is fixed to. Exceed that and you need planning permission, however modest the array.
Two hundred millimetres is not much. A standard in-roof or on-roof domestic panel system fits comfortably. A tilted frame on a flat roof usually does not.
What Class A of Part 14 permits
Class A covers the installation, alteration or replacement of microgeneration solar photovoltaic or solar thermal equipment on a dwellinghouse or a block of flats, and on a building within the curtilage of a dwellinghouse.
The right is conditional rather than absolute. Beyond the projection limit, the equipment must not be higher than the highest part of the roof, excluding any chimney, and the siting has to be chosen so as to minimise the effect on the external appearance of the building and on the amenity of the area.
That siting condition is not decorative. It is a condition attached to the right, so an installation that ignores it is outside Class A and is unauthorised development. In practice it rarely bites on a rear slope and occasionally bites on a prominent front elevation.
Part 14 has been amended several times as national policy on domestic renewables has moved, so read the current consolidated text rather than a summary of the original 2015 order.
The 200 millimetre limit and how it is measured
The measurement is perpendicular to the plane of the surface the equipment is fixed to, taken to the outermost part of the installation.
| Installation | Typical position | Usual outcome |
|---|---|---|
| On-roof panels on rails, pitched roof | 100 to 150 mm above the tile plane | Within the limit |
| In-roof integrated panels | Flush or recessed | Within the limit |
| Tilted frame on a flat roof | Several hundred mm at the high edge | Outside the limit |
| Wall-mounted panels on a vertical elevation | Depends on bracket depth | Usually within, check the fixings |
| Panels over an existing conservatory roof | Depends on mounting | Measure before ordering |
Measure the whole assembly, including the frame, rails and any optimiser housing, rather than the panel thickness alone. Installers quoting a panel depth of 35 mm are describing the module, not the installation.
Where an array sits on more than one plane, each plane is assessed separately. A run that crosses a hip or steps over a dormer can comply on one face and fail on another.
Flat roofs, and why they are the awkward case
Domestic flat roofs, typically on a rear extension or a garage, are where the rule produces a result most homeowners find odd. Panels laid flat on a flat roof generate poorly, so installers tilt them, and a tilt of even fifteen degrees across a two-metre panel lifts the high edge well beyond 0.2 metres from the roof plane.
There are three honest options. Lay the panels flush and accept lower output. Move the array to a pitched roof elsewhere on the property. Or apply for planning permission, which for a rear flat roof screened from public view is frequently granted without difficulty.
What does not work is treating the parapet as the reference plane. The measurement is taken from the roof surface, not from the top of an upstand.
Walls, conservation areas and the highway test
On article 2(3) land, which includes conservation areas and World Heritage Sites, wall-mounted equipment is restricted where the wall fronts a highway. The effect is that a front elevation facing the street is generally outside the right in a conservation area, while a rear or side wall may still qualify.
Article 4 directions are the other constraint to check. A direction can remove Part 14 rights entirely for a defined area, and several authorities have made directions covering conservation areas where solar equipment was affecting the character of a uniform roofscape. The direction is registered as a local land charge and should appear on a search, but checking the council's own list before ordering is quicker.
The related question of which elevation counts as the principal one, and what falls inside the curtilage, comes up constantly across permitted development classes, and our note on curtilage and principal elevation in Class A cases works through how inspectors approach it.
Listed buildings and the separate consent
Permitted development rights and listed building consent are different regimes. A right under Part 14 does not authorise works to a listed building, and installing panels on a listed roof without consent is an offence rather than a planning breach.
Part 14 also contains restrictions relating to scheduled monuments and to buildings within the curtilage of a listed dwellinghouse, so check the current text before assuming a detached garage or outbuilding qualifies.
Where consent is needed, the case usually turns on reversibility, the visibility of the array from public vantage points, the fixing method and its effect on historic fabric, and whether a less prominent roof slope or an outbuilding could take the array instead. A Heritage Statement that describes significance and then addresses each of those points does more than an appeal to carbon reduction, which conservation officers hear daily and weigh as one consideration among several.
Standalone arrays in the garden
Ground-mounted solar within the curtilage of a house falls under a separate class in Part 14, with its own limits covering the number of installations permitted, the maximum height, the minimum distance from the boundary and the total panel area. In designated areas there are additional restrictions on siting relative to a highway.
The practical constraint on most domestic plots is the boundary distance. A garden array that has to sit several metres clear of every boundary rules out the majority of urban gardens before the area limit is reached.
The removal condition and what it means
Class A carries a condition that the equipment be removed as soon as reasonably practicable when no longer needed for microgeneration. Nobody enforces this routinely, but it matters on sale, because a redundant array on a roof is a live breach rather than a historic one.
It also matters for replacement. Swapping panels for a larger or deeper system is an alteration, and the same limits apply afresh, so a replacement that projects further than the original needs permission even though the original did not.
One honest caveat. The only formal way to confirm that an installation is lawful is a lawful development certificate under section 192 of the Town and Country Planning Act 1990, applied for before the work. Installer assurances carry no weight with a council or a buyer's solicitor, and a certificate costs less than removing a non-compliant array. A short Planning Statement setting out the measurements and the class relied on is usually all the supporting material a certificate application needs.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Enter your postcode on PlanScope to check what a solar installation on your property is likely to need.
Frequently asked questions
Do I need planning permission for solar panels on my house?
Usually not. Class A of Part 14 of the GPDO 2015 permits solar photovoltaic and solar thermal equipment on a dwellinghouse, subject to conditions. The main limits are that equipment must not project more than 0.2 metres from the roof or wall plane and must not exceed the height of the roof excluding chimneys.
How is the 0.2 metre projection measured?
Perpendicular to the plane of the roof slope or wall, to the outermost part of the installation. That includes the mounting rails, frame and any housings as well as the panel itself. Where an array crosses more than one roof plane, each plane is measured separately and can produce a different answer.
Can I put tilted panels on a flat roof?
Rarely within permitted development. A tilt sufficient to generate usefully lifts the high edge well beyond 0.2 metres from the roof plane, which takes the installation outside Class A. Options are laying the panels flush, using a pitched roof elsewhere on the property, or applying for planning permission.
Are solar panels allowed in a conservation area?
Often, but with restrictions. On article 2(3) land, wall-mounted equipment on a wall fronting a highway is outside the right, and an Article 4 direction may remove Part 14 rights for the area entirely. Check the council's list of directions before ordering equipment.
What about a listed building?
Listed building consent is a separate requirement that permitted development rights do not displace, and unauthorised works to a listed building are a criminal offence. Applications usually turn on reversibility, visibility from public viewpoints, the fixing method and whether a less prominent roof slope or outbuilding could take the array.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.