Do You Need Planning Permission for a Conservatory?

A conservatory is an extension, not a special case

• There is no separate permitted development right for conservatories. They are assessed under Class A, the same rules as any single-storey rear or side extension, which is why the answer depends on the shape of your house rather than on the glazing.

• Conservatories get one concession the rest of Class A does not: the condition requiring exterior materials to be of similar appearance to the existing house expressly excludes materials used in the construction of a conservatory. (MHCLG, September 2019)

The size limits that decide it

• A single-storey rear extension may project 3 metres from the rear wall of the original house, or 4 metres if the house is detached, and must not exceed 4 metres in height. (MHCLG, September 2019)

• Those depths double to 6 metres and 8 metres under the larger home extension route, which needs a prior approval application to the council rather than full planning permission. The route is not available on article 2(3) land or a site of special scientific interest. (MHCLG, September 2019)

• A prior approval application for a larger home extension costs £249, against £548 for a full householder application. (Planning Portal, April 2026)

• Total ground covered by buildings other than the original house must not exceed 50% of the curtilage. Existing extensions, sheds and detached garages all count towards that 50%, including ones built before 1948. (MHCLG, September 2019)

• Within 2 metres of a boundary the eaves must not exceed 3 metres. A side-facing conservatory must also be single storey, no more than 4 metres high, and no wider than half the width of the original house. (MHCLG, September 2019)

When a conservatory always needs permission

• Anything forward of the principal elevation, or beyond a side elevation that fronts a highway, is outside permitted development and needs planning permission. (MHCLG, September 2019)

• On article 2(3) land, which includes conservation areas, National Parks, AONBs, the Broads and World Heritage Sites, side extensions and rear extensions of more than one storey are not permitted development, and cladding is excluded. (MHCLG, September 2019)

• The height of the extension must not exceed the height of the highest part of the existing roof, and its eaves must not exceed the height of the existing eaves. (MHCLG, September 2019)

Building regulations and conservatories

• Conservatories are often exempt from building regulations where they are at ground level, under 30 square metres, separated from the house by external-quality doors, and have an independent heating system. Remove the separating doors or run the house heating into it and the exemption usually falls away.

• That exemption is about building control, not planning. The two are decided separately and by different teams at the same council.

Common questions

How big can a conservatory be without planning permission?

Three metres deep from the original rear wall on an attached house, four on a detached house, and no more than four metres high. Six and eight metres are possible through the larger home extension prior approval route, which is an application to the council but not a full planning application.

Do I need planning permission for a conservatory in a conservation area?

A rear conservatory may still be permitted development, but the larger 6m and 8m route is not available, side extensions are excluded, and the limits are tighter. Check before you design it, because this is where most conservation-area refusals come from.

Does a conservatory count towards the 50% rule?

Yes. The conservatory, any existing extensions, sheds and detached garages together must not cover more than half the area of the curtilage, excluding the footprint of the original house.

Sources