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 Southwark

House extension plans in Southwark, £895 fixed

Southwark's Householder Development SPD (adopted 7 July 2025) says rear extensions between 3m and 6m deep need to consider the impact on neighbours, especially on the boundary wall, and the roof should slope down to stay below 2.4m at the boundary. Rear extensions over 6m deep on the boundary are likely to be refused.

Planning drawings£895
Building regs£795
Council fee£548
Get your fixed feeFFP-01 · Rev A
Our fixed fee£895
Council fee, paid to your council£548
Our fee + council fee£1,443
CoverageAll 33 boroughs

Householder application fee, paid to your council at submission.

Plus the Planning Portal's own charge if the application goes through the Portal: up to £149 including VAT, depending on the application type, and some types have none (source).

Get this fee in writing

or email hello@fixedfeeplans.co.uk

No obligation. Nothing is sent until you ask; your enquiry comes to us and nowhere else.

Starts at£150
Boroughs33/33
Stages5

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 Southwark Council asks of a house extension

From the council's Householder Development SPD (adopted 7 July 2025, council page).

  • Rear extensions between 3m and 6m in depth need to consider the potential impact on neighbours, especially if on the boundary wall; the roof should be designed to slope down towards the neighbouring property and to remain below 2.4m at the boundary for the entire length of the extension. (source, checked 15 October 2026)
  • Rear extensions which exceed 6m in depth on the boundary are likely to be refused. (source, checked 15 October 2026)
  • Rear extensions must not take up more than 50% of the total rear garden space. (source, checked 15 October 2026)
  • The SPD recommends, for rear extensions needing planning permission, a maximum height of 4m, a depth below 6m and a maximum height of 2.4m for the sloped-down part. (source, checked 15 October 2026)
  • Where the house has a rear outrigger, an L-shaped or wrap-around extension should remain no deeper than 6m on the boundary and stay below 2.4m at the eaves, should not close off the outrigger window as a source of light (a courtyard may be needed), and must not take up more than 50% of the total rear garden space. (source, checked 15 October 2026)

What Southwark house extension drawings have to show

Southwark measures against the boundary, so the drawings show the depth of the extension along each boundary wall, and a section with the roof sloping down towards the neighbouring property and staying below 2.4m at the boundary for the entire length of the extension. The SPD says rear extensions which exceed 6m in depth on the boundary are likely to be refused, and that rear extensions must not take up more than 50% of the total rear garden space, so the garden area is worked out on the plan. For extensions needing planning permission it recommends a maximum height of 4m, a depth below 6m and a maximum height of 2.4m for the sloped-down part.

Where the house has a rear outrigger, an L-shaped or wrap-around extension should remain no deeper than 6m on the boundary and stay below 2.4m at the eaves. The SPD says it should not close off the outrigger window as a source of light, and a courtyard may be needed, so the drawings show how that window is lit afterwards. The same 50% garden limit applies. We have taken only the SPD's planning-permission guidance here; what permitted development allows is a separate question, answered by the permitted development rules and not by this SPD.

The council's householder checklist (checked 10 October 2026) asks for a fire safety strategy or a reasonable exception form (London Plan Policy D12) and CIL information with every application, and a site plan at 1:100 or 1:50 that labels and numbers every immediately adjoining building, with elevations of the front, back and both sides. Personal information in documents can invalidate an application. On the Sunray Estate Conservation Area, external alterations on Sunray Avenue, Sunray Gardens, Casino Avenue, Nairne Grove and parts of Red Post Hill and Herne Hill need planning permission under a direction confirmed on 13 November 1987. The SPD was adopted on 7 July 2025, and we checked it on 15 October 2026.

Southwark guidance · rear depth

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

On the boundary (beyond this, likely refused)6 mDepth beyond the original rear wall · dashed line: permitted development
Source: Householder Development 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

Southwark: 558 householder decisions

Southwark
Approvals, prior approvals included94.8%

529 of 558 granted. London: 85.8%.

Decided within 8 weeks97.5%

424 of 435 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 Southwark

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

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

Answers

Southwark house extension questions

How deep can a rear extension be in Southwark?
The SPD says rear extensions between 3m and 6m deep need to consider the impact on neighbours, especially on the boundary wall, and rear extensions which exceed 6m in depth on the boundary are likely to be refused. For extensions needing planning permission it recommends a depth below 6m. Rear extensions must not take up more than 50% of the total rear garden space.
How high can a Southwark extension be on the boundary?
For rear extensions between 3m and 6m deep, the SPD says the roof should be designed to slope down towards the neighbouring property and to remain below 2.4m at the boundary for the entire length of the extension. For extensions needing planning permission it recommends a maximum height of 4m, and a maximum of 2.4m for the sloped-down part.
Can I build a wrap-around extension in Southwark?
Where the house has a rear outrigger, the SPD says an L-shaped or wrap-around extension should remain no deeper than 6m on the boundary and stay below 2.4m at the eaves. It should not close off the outrigger window as a source of light, so a courtyard may be needed, and it must not take up more than 50% of the total rear garden space.

Start with £150

Your fixed fee is already on this page.

Tell us the postcode and what you want to build. We confirm the fee in writing and book the survey.

Get my fixed fee020 7864 7245
01
Measured surveyWithin five working days
£150
02
Existing drawingsThe building as it stands
£200
03
Proposed drawingsYour scheme, revised until right
£250
04
Planning application packForms, statements, OS plans
£150
05
Submission and agent servicePortal submission, queries handled
£145
Total, planning application£895