Two Victorian terraced houses on a London street, one painted white and one in yellow stock brick, with bay windows
Floor plan drawings, pencil sketches of a house, a scale rule and a protractor spread across a desk
Photo: Tima Miroshnichenko / Pexels

House extension plans · London Borough of Lewisham

House extension plans in Lewisham, £895 fixed

Lewisham's Alterations and Extensions SPD (24 April 2019) says rear extensions should generally not be more than 3m deep for terraced or semi-detached properties, and that under no circumstances should an extension take up more than half the depth of the original rear garden or yard. For infills and wrap-arounds, outbuildings count in garden depth.

Planning drawings£895
Building regs£795
Council fee£548
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Boroughs33/33
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Photo: Huy Phan / Pexels

The back of a house extension at shell stage, with a large glazed opening, blockwork walls and a scaffold tower
An extension at shell stage: the opening, the blockwork and the beam above it are what the building regulations drawings describe. Photo: Brett Jordan / Pexels.

What Lewisham Council asks of a house extension

From the council's Alterations and Extensions SPD (adopted 24 April 2019, council page).

  • Rear extensions should generally not be more than 3m deep for terraced or semi-detached properties. Deeper extensions may be acceptable for detached properties or on large plots. (source, checked 14 October 2026)
  • Under no circumstances should the extension take up more than half the depth of the original rear garden or yard. For infill and wrap-around extensions, the SPD adds that outbuildings are taken into consideration in working out garden depth (they reduce the depth of the remaining garden). (source, checked 14 October 2026)
  • As a general rule, extensions extending up to 3m in length should be no more than 3m in height on the boundary. Extensions which exceed this length and exceed a height of 2.5m on the boundary are unlikely to be supported. (source, checked 14 October 2026)
  • Where a pitched roof is proposed, the ridge height should be visibly lower than the sill of any first floor windows (a minimum of 2 or 3 brick courses). (source, checked 14 October 2026)
  • Infill and wrap-around extensions beside an original rear projection should be no more than one single storey in height. (source, checked 14 October 2026)
  • Two or more storey side extensions should be set in at least 1m from the boundary and set back at least 1m from the front elevation; where it is appropriate to build to the boundary, the setback from the front elevation should be at least 2m. (source, checked 14 October 2026)
  • It is unlikely to be possible to use the roof of an extension as a terrace unless it can be demonstrated that there would be no unacceptable impact on neighbouring properties' privacy. (source, checked 14 October 2026)

What Lewisham house extension drawings have to show

Lewisham's SPD sets a handful of measured limits, so the drawings carry each as a dimension. Rear depth is shown against the 3m the SPD says terraced and semi-detached extensions should generally not exceed. The extension is shown against half the depth of the original rear garden or yard, a limit the SPD says is not to be passed under any circumstances (for infill and wrap-around extensions, outbuildings are taken into consideration in working out garden depth), and a pitched ridge is drawn visibly lower than the sill of any first floor window, a minimum of 2 or 3 brick courses.

Height on the boundary is dimensioned too: no more than 3m for an extension up to 3m long, and an extension that exceeds that length and 2.5m on the boundary is unlikely to be supported. A two or more storey side extension is drawn set in at least 1m from the boundary and back at least 1m from the front elevation, or at least 2m back where it is appropriate to build to the boundary. Using the roof of an extension as a terrace is unlikely to be possible unless it can be demonstrated that there would be no unacceptable impact on neighbours' privacy.

The council's householder checklist, which it links as its list from October 2022, asks for block plans at 1:500 and a scale bar on every plan and drawing showing 1 metre and 10 metres and the direction of north. It also wants a site survey with datum points and contours and street elevations showing the proposal against the existing streetscene. The council consulted on a revised draft until 29 September 2026; no final revised list had replaced the 2022 one when we checked on 14 October 2026. If an application is invalid you have 21 days to supply what is missing.

Lewisham guidance · rear depth

How deep Lewisham expects a single-storey rear extension to be

Terraced or semi-detached3 mDepth beyond the original rear wall · dashed line: permitted development
Source: Alterations and Extensions SPD. The marker shows the national permitted development depth (GPDO 2015, Schedule 2, Part 1, Class A, A.1(f): 4 m detached, 3 m otherwise), which applies only where no application is needed.
Permitted development · Class A

How far a single-storey rear extension can go before it needs more than a drawing

Terraced or semi-detached

Existing houseNo applicationPrior approvalPlanning application3 m6 mDepth beyond the original rear wall

Detached

Existing houseNo applicationPrior approvalPlanning application4 m8 mDepth beyond the original rear wall

Height, side view

HouseBoundary2 m4 m maxoverall height3 m eaveswithin 2 m of boundary
Source: GPDO 2015, Schedule 2, Part 1, Class A: A.1(f) (3 m, or 4 m if detached; 4 m high), A.1(g) (6 m, or 8 m if detached; not on article 2(3) land such as conservation areas, nor on a site of special scientific interest), A.1(i) (eaves over 3 m within 2 m of a boundary) and the prior approval procedure in A.4. Terraced and semi-detached houses are the “any other dwellinghouse” case. Other conditions still apply: check the permission section and run the checker.
PS2 · at a glance

Lewisham: 578 householder decisions

Lewisham
Approvals, prior approvals included89.4%

517 of 578 granted. London: 85.8%.

Decided within 8 weeks95.2%

393 of 413 applications, prior approvals excluded.

Source: MHCLG PS2, 1 July 2025 to 30 June 2026. Dark tick: London.
A bright kitchen with white cabinets, a stainless steel range cooker and extractor hood, and a window over the sink
A kitchen in a rear extension: the wide opening into it from the old house is carried by a beam. Photo: Curtis Adams / Pexels.

What it costs in Lewisham

  • Planning drawings: £895, plus £548 to Lewisham Council.
  • Building regulations drawings: £795.

House extension plans across London · Lewisham planning rules · every price

Answers

Lewisham house extension questions

How deep can a rear extension be in Lewisham?
The SPD says rear extensions should generally not be more than 3m deep for terraced or semi-detached properties. Deeper extensions may be acceptable for detached properties or on large plots. Under no circumstances should the extension take up more than half the depth of the original rear garden or yard.
How high can an extension be on the boundary in Lewisham?
As a general rule, the SPD says extensions up to 3m in length should be no more than 3m high on the boundary. Extensions that exceed that length and exceed 2.5m in height on the boundary are unlikely to be supported. Where a pitched roof is proposed, the ridge should be visibly lower than the sill of any first floor windows, by a minimum of 2 or 3 brick courses.
Does Lewisham count my garden shed when it measures garden depth?
For an infill or wrap-around extension, yes: the SPD says that in working out garden depth, outbuildings are taken into consideration, because they reduce the depth of the remaining garden. Under no circumstances should the extension take up more than half the depth of the original rear garden or yard, so put the outbuilding on the drawing before measuring.
How far from the boundary must a two-storey side extension be in Lewisham?
The SPD says two or more storey side extensions should be set in at least 1m from the boundary and set back at least 1m from the front elevation. Where it is appropriate to build to the boundary, the setback from the front elevation should be at least 2m. Infill and wrap-around extensions beside an original rear projection should be no more than one single storey in height.

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