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Garden rooms in London

Updated 22 October 2026

Planning permission in London

Garden rooms count as outbuildings. Most can be built without planning permission if they sit behind the front of the house, have eaves no higher than 2.5m, and together with other buildings cover no more than half the garden. If any part of the room is within 2m of a boundary, the whole building must be no more than 2.5m tall; otherwise the limit is 4m with a dual-pitched roof, or 3m for any other roof. It must be single storey, with no veranda, balcony or raised platform over 30cm.⁴ In the grounds of a listed building, any garden room needs permission, and so does a room used as primary living space, such as a bedroom.⁵ Our planning permission guide explains every rule.

If you live in a flat or maisonette, you'll need planning permission for any garden room, even a small one. In London that's 54% of households.¹

Conservation areas and Article 4 directions

On designated land, which includes National Landscapes (the new name for Areas of Outstanding Natural Beauty) and conservation areas, you can't build a garden room to the side of the house without permission.⁶ In a National Landscape, national park or World Heritage Site, buildings more than 20m from the house can also cover no more than 10m² in total.⁴

Many boroughs go further with Article 4 directions, which remove permitted development rights in particular areas. Islington has removed some rights in 40 of its 42 conservation areas, mainly for changes like doors, windows and brickwork.⁷ Lambeth has directions in nine conservation areas that cover "external building alterations or other built development".⁸ If you're in a conservation area, ask your borough whether a direction covers garden buildings before you order.

Part of Bromley lies in the Kent Downs National Landscape⁹, so the stricter rules for National Landscapes apply there.

Small gardens and close neighbours

London gardens are tight. One in five London households has no garden at all, the highest share in Great Britain.³ In a small garden the 2.5m height limit within 2m of a boundary usually decides the design, so flat or shallow roofs are common.

If you build a wall on the boundary, or dig foundations within 3m of a neighbour's building and deeper than its foundations, the Party Wall Act may mean you need to give notice first.¹⁰ Ground screws or a light timber base usually avoid deep digging. See our foundations guide.

Building regulations

Building regulations don't normally apply to a garden room under 15m² with no sleeping accommodation, or one of 15m² to 30m² with no sleeping accommodation that is at least 1m from every boundary or built mostly of non-combustible materials.¹¹ Running a new electrical circuit to it is notifiable work, so use a registered electrician. See our building regulations guide.

Which council to ask

Planning in London is handled by the 32 boroughs and the City of London.¹² Around Old Oak and Park Royal, in parts of Brent, Ealing and Hammersmith and Fulham, the Old Oak and Park Royal Development Corporation is the planning authority instead.¹³

What a garden room costs in London

Installed garden rooms typically cost £1,200 to £2,500 per m² across the UK¹⁴, and one industry cost guide puts London and the South East 15% to 25% higher.¹⁵ So a 4m x 3m room in London might cost roughly £16,500 to £37,500 before extras. Tight access through a house or side passage can add to the cost of delivery and building, so mention it when you ask for quotes.

With the average London home at £554,430 in August 2026¹⁶, a garden room is a small share of a typical home's value.

Questions people ask

Do I need planning permission for a garden room in London?

If you live in a house and the room meets the national size and height limits, usually not. Flats and maisonettes always need permission, and some conservation areas have Article 4 directions that remove rights, so check with your borough.

Can I build a garden room in a small London garden?

Yes, but within 2m of a boundary it can be no more than 2.5m tall, which suits flat or shallow roofs. Keep it to no more than half the garden together with other buildings.

Do I need a party wall agreement for a garden room?

Only if the work is covered by the Party Wall Act, such as building on the boundary line or digging foundations close to a neighbour's building. Ground screws usually avoid this.

Related guides

Sources

1. Office for National Statistics, Housing, England and Wales: Census 2021.
2. Mayor of London, The London Plan 2021, chapter 7: heritage and culture.
3. Office for National Statistics, One in eight British households has no garden, May 2020.
4. Planning Portal (England), Outbuildings: mini guide. Permitted development limits for outbuildings.
5. Ministry of Housing, Communities and Local Government, Permitted development rights for householders: technical guidance.
6. Planning Portal, Outbuildings. Designated land rules for outbuildings.
7. Islington Council, Permitted development.
8. Lambeth Council, Article 4 directions.
9. London Borough of Bromley, Local plan maps: key to designations.
10. RICS, Party walls.
11. Planning Portal (England), Outbuildings: building regulations. When building regulations normally apply to outbuildings.
12. London Councils, London Councils.
13. Mayor of London, OPDC: about us.
14. MyBuilder, Garden room cost price guide, updated 21 October 2026. UK price ranges for garden rooms, foundations, electrics, plumbing and fees.
15. BestBuilders, Garden room cost UK, updated 7 September 2026. An industry cost guide, not official data.
16. HM Land Registry, UK House Price Index summary: August 2026, published 21 October 2026.