Lambeth does not publish a depth limit for rear extensions. It judges the back of the house, so we study the closet return, the stepped wall and the neighbours before we draw anything.
Look for a figure in metres in Lambeth's Design Guide Part 4 (August 2023) and you will not find one for a standard rear extension. The guide works from policy tests instead: a positive response to the host building, subordination to it, and protection of the neighbours' amenity. Two houses on the same street can get different answers because the test is the relationship between the extension and the particular back wall.
For a full-width box across the back, the guide says this may be the most desirable form, with a glazed elevation to the garden. It then asks for refinement where the house has a stepped rear elevation, especially a non-designated heritage asset or a house in a conservation area. Stepping the facade and adding brick piers between the glazing is its worked example, aimed at lessening the boxy, horizontal effect of a wall of glass. Full-width extensions are unlikely to be acceptable on statutorily listed buildings.
Closet returns are the Lambeth detail that catches people out. These are the narrow additions at half-landing level on early and mid-19th century houses with rear staircases. The guide says they are generally no deeper than they are wide, and that demolishing them will generally be resisted, especially where they form part of a group of similar houses. A scheme that starts by removing the closet return is the one most likely to be sent back.
Four tests in the guide shape the drawings for a Lambeth rear extension.
| House feature | What the guide says | How we draw it |
|---|---|---|
| Full-width rear box | May be desirable; refine stepped rears to lessen the boxy effect | Facade stepping and piers shown on the elevation |
| Closet return | Demolition generally resisted; new ones must follow the local pattern | Existing return kept and shown in plan and section |
| Side space above ground floor | Minimum 1 metre retained between extension and boundary | Setback dimensioned on the first-floor plan |
| Neighbours | Amenity and outlook are key considerations for any new closet or extension | Neighbour windows measured and shown |
Lambeth Council, Design Guide Part 4: Building Alterations, Extensions and Retrofit, August 2023.
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Lambeth's Article 4 page lists nine conservation areas where all or part of the area has directions removing permitted development for external alterations: Albert Square, Hyde Farm, Lansdowne Gardens, Leigham Court Estate, Park Hall Road, St Marks, Stockwell Park, Streatham Lodge and Vauxhall. In those areas, planning permission is required for the works listed in the direction. The council's page links a dataset so you can check an address.
For example, a Victorian house in the Hyde Farm area near Balham needs the direction read before anyone talks about 3 metres. A similar house a few streets outside any direction may qualify for a lawful development certificate. We read the direction for your address first, because it decides which of the two routes is open.
On the paperwork side, Lambeth has been piloting an online householder application tool and says a householder project should get a response in 8 weeks. Its 2024 Local List sets out what else it may ask for, and we check each item against your scheme before submitting.
Every figure is linked to the page or document we read.
Lambeth's Design Guide Part 4 of August 2023 says closet returns are generally no deeper than they are wide and that their demolition will generally be resisted.
Source: Lambeth Council, Design Guide Part 4: Building Alterations, Extensions and Retrofit, para 4.47The same guide says a side extension should retain a minimum of 1 metre between the extension and the property boundary above ground floor level.
Source: Lambeth Council, Design Guide Part 4, para 4.68Lambeth lists 9 conservation areas with Article 4 directions on external alterations: Albert Square, Hyde Farm, Lansdowne Gardens, Leigham Court Estate, Park Hall Road, St Marks, Stockwell Park, Streatham Lodge and Vauxhall.
Source: Lambeth Council, Article 4 DirectionsLambeth says a householder project on an existing home should get a response in 8 weeks, and its online householder tool is a pilot.
Source: Lambeth Council, Apply for householder planning permissionLambeth's Local Information Requirements (the Local List) of 2024 set out what else a planning application must include beyond the national list.
Source: Lambeth Council, Local Information Requirements 2024Lambeth decided 354 householder applications between July 2025 and June 2026, prior approvals excluded, and 333 of them were decided within 8 weeks.
Source: MHCLG, Planning application statistics PS2, July 2025 to June 2026Permitted development allows a single-storey rear extension up to 4 metres on a detached house or 3 metres on any other house.
Source: legislation.gov.uk, GPDO 2015, Schedule 2, Part 1, Class ATell us about your project and get a fixed, no-obligation quote back within one working day. If you don't need planning permission at all, we'll tell you that too — for free.
Lambeth sets no published depth figure in its Design Guide Part 4. Each scheme is judged against its host building and its neighbours' amenity. Permitted development, where it applies, allows 3 metres on most houses and 4 on a detached one.
Lambeth's guide says the demolition of closet returns will generally be resisted, especially where they belong to a group of similar properties. A scheme that keeps and builds beside the return is much more likely to be accepted.
Albert Square, Hyde Farm, Lansdowne Gardens, Leigham Court Estate, Park Hall Road, St Marks, Stockwell Park, Streatham Lodge and Vauxhall. Planning permission is required in them for the works the direction lists.
It can be, and the guide calls a simple full-width box the most desirable form for many houses. Where the rear wall is stepped, especially on older houses or in conservation areas, it asks for the facade to be stepped with piers between the glazing. It is unlikely to be acceptable on listed buildings.
£765 inc survey (£565 if you supply measured drawings). That covers the measured survey, the drawings and the submission, with free revisions until the council decides. Lambeth's own application fee is separate and goes to the council.
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