Southwark Extension Guide: Planning, Costs & Conservation Areas 2026
Southwark runs from Dulwich Village to Old Kent Road, and its planning landscape is just as wide. Forty-eight conservation areas, a Local Plan adopted in 2022, a new Householder Development SPD, and an HMO Article 4 direction that covers far less of the borough than people assume. Here is what actually applies before you extend.
TL;DR - The Quick Answer
Southwark has 48 conservation areas, including Dulwich Village, Dulwich Wood, Camberwell Grove, Camberwell Green and Peckham Hill Street. The council's Local Plan, the Southwark Plan 2022, was adopted on 23 February 2022, and a new Householder Development SPD was adopted in July 2025 setting out the guidance homeowners are assessed against. Southwark's HMO Article 4 direction is partial, covering only Henshaw Street SE17 and Bywater Place SE16, not the whole borough, so most standard house extensions are unaffected by it. Separate Article 4 directions cover the Sunray Estate in north Dulwich and part of Dulwich Wood ward through the Great North Wood direction, requiring planning permission for development in those specific areas. Outside conservation areas, national permitted development rights apply in full. Extension costs run at the London-wide baseline of £3,200-£4,600 per m², with a 5-10% premium for conservation area work. Planning fees are £548 for a householder application and £274 for a Lawful Development Certificate.
Southwark: A Borough of Contrasts
Southwark stretches from the riverside at Bermondsey and Borough, through the dense Victorian terraces of Camberwell, Peckham and Nunhead, to the leafy conservation areas of Dulwich in the south. Few London boroughs cover this much ground in housing character: large Edwardian villas on generous plots sit a few miles from purpose-built council estates and post-war infill, and the planning approach genuinely differs between them.
That range means the single most useful thing any Southwark homeowner can do before designing an extension is establish precisely where their property sits: which of the 48 conservation areas (if any) applies, whether an Article 4 direction affects the specific street, and which supplementary planning guidance the council will assess the scheme against.
Housing character by area
Large Edwardian and Victorian houses on generous plots, plus substantial semis. Dulwich Village and Dulwich Wood are both conservation areas, and the whole of East Dulwich, Herne Hill and Dulwich Village falls within the council's dedicated Dulwich SPD, which gives area-specific design guidance on top of the borough-wide policies.
Georgian and Victorian terraces, several within conservation areas covering Camberwell Grove, Camberwell Green and Camberwell New Road. No borough Article 4 direction applies here beyond the standard conservation area controls that already come with that designation nationally.
Victorian terraces and inter-war housing. Peckham Hill Street and Rye Lane Peckham are designated conservation areas, alongside Nunhead Cemetery, Nunhead Green and Honor Oak Rise. Much of the wider area sits outside any conservation area boundary.
A mix of Victorian terraces (Walworth Road is a conservation area), council estates, and modern flats. Regeneration around Elephant & Castle and Old Kent Road has brought significant new-build housing. Conservation coverage is lighter here than in Dulwich or Camberwell.
The Southwark Plan 2022 and the Householder Development SPD
Southwark's Local Plan, known as the Southwark Plan 2022, was adopted by the council on 23 February 2022 and covers the period 2019 to 2036. It is the starting point for assessing any planning application in the borough, including householder extensions.
In July 2025, the council adopted a new Householder Development Supplementary Planning Document (SPD), replacing a 2015 technical update to the borough's residential design standards. This is the current guidance homeowners and their design teams are assessed against for rear, side and roof extensions, and it sits alongside a separate Dulwich SPD (adopted 2013), which gives additional, area-specific guidance for East Dulwich, Herne Hill, Dulwich Village and a small area to the west of Peckham Rye.
Southwark's planning policy documents at a glance
For a property inside Dulwich, both the Householder Development SPD and the Dulwich SPD apply together, which is one reason schemes there are typically assessed more closely than an equivalent extension in, say, East Dulwich's eastern edge or Peckham.
Conservation Areas in Southwark
Southwark has 48 conservation areas, one of the highest counts of any London borough. They range from small historic enclaves around Borough and Bermondsey to large residential areas covering entire streets in Dulwich, Camberwell and Peckham.
Conservation areas most relevant to house extensions
Dulwich Village and Dulwich Wood
Large Edwardian and Victorian houses on generous plots. Assessed against both the Householder Development SPD and the area-specific Dulwich SPD, which is the closest thing Southwark has to a bespoke design code for extensions.
Camberwell Grove, Camberwell Green and Camberwell New Road
Georgian and Victorian terraces. Standard conservation area controls apply: rear extensions need full planning permission, and materials matching the existing brick and roofline are expected.
Peckham Hill Street and Rye Lane Peckham
Victorian terraces around Peckham's historic core. Extensions visible from the street or affecting the roofline require planning permission and sympathetic materials.
Nunhead Cemetery, Nunhead Green and Honor Oak Rise
Smaller conservation areas covering historic green spaces and the surrounding residential streets in the south east of the borough.
Walworth Road
Covers the historic high street and adjoining residential streets. The wider Walworth and Elephant & Castle area outside this boundary carries no conservation designation.
Being in a conservation area brings planning restrictions in its own right, independent of any separate Article 4 direction. Southwark's own guidance is explicit that in a conservation area you need planning permission to make minor roof alterations, change windows, or install satellite dishes, none of which would require permission on an equivalent house outside a conservation area. Confirm your exact boundary before assuming standard permitted development limits apply; conservation area lines can run down the middle of a street, and Southwark Maps lets you check by address.
Article 4 Directions in Southwark: Narrower Than You'd Think
Southwark maintains eleven active Article 4 directions, but they are targeted at specific issues and specific locations rather than applied blanket-wide across the borough's conservation areas. It is a common assumption that a house in a Southwark conservation area automatically loses its permitted development rights for extensions under Article 4. In most of the borough, that is not accurate.
The directions that actually exist
- HMO conversions (Class L): partial coverage only, limited to Henshaw Street SE17 (C3 to C4 conversions for 4-6 people) and Bywater Place SE16 (house to HMO for 3-6 people). The rest of the borough retains permitted development rights for small HMO conversion.
- Sunray Estate: a distinct pocket in north Dulwich bordering Herne Hill (Sunray Avenue, Sunray Gardens, Casino Avenue, Nairne Grove, Red Post Hill), where planning permission is required for development. This is separate from the main Dulwich Village conservation area.
- Great North Wood: covers Dulwich and Sydenham Hill Woods and part of Dulwich Wood ward (Grange Lane, Woodhall Drive, Great Brownings, Crescent Wood Avenue, part of College Road), requiring planning permission for development in that specific pocket.
- The remaining directions cover railway arches, Class E to residential conversions, demolition of commercial or residential buildings, public houses, the Central Activities Zone, a small number of named sites, and telecommunications equipment near Croxted Road and Norwood Road. None of these affect a standard householder rear or side extension.
The practical takeaway: if you are extending a house you live in in Camberwell, Peckham, Nunhead, or the main body of Dulwich Village, no Southwark Article 4 direction removes your permitted development rights for that extension. Your permitted development rights are affected by whether you are in a conservation area at all (which brings its own national restrictions on roof, window and render works), not by an additional council-specific Article 4. The exceptions are the specific streets named above, plus anyone planning to convert a house into a small HMO anywhere in the borough outside Henshaw Street and Bywater Place, where standard permitted development for that change of use still applies today. For how this compares with other boroughs, see our Article 4 HMO borough guide, which lists Southwark among the boroughs with partial rather than borough-wide HMO coverage.
Permitted Development for Southwark's Terraces
Outside the 48 conservation areas and the small Article 4 pockets covered above, national permitted development rules apply in full across Southwark. Given how much of the borough is genuinely terraced housing, the terraced-house limits are the ones that matter for most homeowners here.
| Extension type | PD limit | Prior approval limit |
|---|---|---|
| Single-storey rear (terraced/semi) | 3m depth | Up to 6m |
| Single-storey rear (height) | 4m max (3m eaves within 2m of boundary) | Same height limits apply |
| Side extension | Half width of original house | N/A - full planning if over PD limit |
| Two-storey rear | 3m depth, 7m from rear boundary | N/A - almost always full planning in practice |
| Loft conversion (rear dormer) | 40m³ (terraced), volume added to roof space | N/A |
Flats have no permitted development rights
Permitted development rights under Part 1 of the GPDO apply only to houses (use class C3 dwellinghouses), not flats. If you live in a flat, even a ground floor flat with its own private garden, any external works, including an extension, require a full planning application.
This affects a significant share of Southwark's housing, particularly Victorian conversions in Camberwell and Peckham and purpose-built blocks around Elephant & Castle and Old Kent Road.
As with other terraced boroughs, depth limits are measured from the property's original rear wall, not the current one. Many Victorian terraces in Camberwell and Peckham were built with a single-storey rear outrigger, which changes where that 3m or 6m measurement legally starts. Get a measured survey before assuming a side return infill or full-width rear extension fits within permitted development. Our guides to side return extensions and terraced house extensions cover this measurement question in detail, and our conservation area extension guide covers what changes once permitted development is off the table.
Extending a Flat in Southwark
Flats make up a large share of Southwark's housing stock, from Victorian conversions in Camberwell and Peckham to purpose-built blocks around Elephant & Castle and Old Kent Road. As covered above, flats have no permitted development rights, so any external works to a flat, including a rear extension to a ground floor flat with its own private garden, need a full planning application.
Most Southwark flats are leasehold, which means you own the right to occupy the flat but the freeholder owns the structure and external walls. A flat extension changes the building envelope, so before planning permission you need a licence to alter, formal written consent from the freeholder describing the proposed works and setting conditions. This typically takes two to four months. The freeholder cannot unreasonably withhold consent, but can charge for their surveyor and legal costs. If you share the freehold with other leaseholders, the process is usually simpler, but the legal requirements are the same.
Planning basics for Southwark flats
For the full process, costs, and leasehold detail, see our guide to extending a flat in London.
Planning Applications in Southwark
When full planning permission is required, applications are assessed against the Southwark Plan 2022, the Householder Development SPD, and, for Dulwich properties, the Dulwich SPD alongside it. Applications are submitted through Southwark's planning portal.
Application process
Terraced housing in Camberwell, Peckham and parts of Nunhead means most extensions in Southwark also trigger the Party Wall Act 1996, which applies whenever foundations are excavated within 3m of a neighbouring structure. Serve notice at least two months before work starts, and budget for a party wall surveyor on each side of a shared boundary.
Extension Costs in Southwark 2026
Our London extension costs guide for 2026 sets a London-wide baseline of £3,200-£4,600 per m², and names Southwark, alongside Lewisham and Greenwich, as one of the South London boroughs that sits at that baseline rather than carrying a discount or a premium. Conservation area work, which covers a meaningful share of Southwark given its 48 designated areas, adds 5-10% on top for matching materials and additional design scrutiny.
The figures below apply the London-wide baseline rate directly to typical Southwark extension sizes, since Southwark carries no borough-specific discount or premium in our costs model. They are a derived estimate, not independent Southwark-specific project data. All figures include VAT at 20% and cover construction cost only (not kitchen fit-out, professional fees, or contingency).
| Extension type | Typical size | Construction cost (inc VAT) | All-in estimate |
|---|---|---|---|
| Single-storey rear | 3m × 5m (15m²) | £48k–£69k | £58k–£83k |
| Side return (infill) | 2m × 8m (16m²) | £51k–£74k | £61k–£88k |
| Loft conversion (dormer) | 25–35m² | £44k–£84k | £52k–£100k |
| Two-storey rear extension | 3m × 5m × 2 (30m²) | £96k–£138k | £115k–£166k |
| Wrap-around (side return + rear) | 35–45m² | £112k–£180k | £134k–£216k |
Conservation area premium: add 5-10% in any of Southwark's 48 conservation areas, higher in Dulwich where the dedicated SPD typically calls for traditional materials and a more subservient design.
| Extension type | Typical size | Construction cost (inc VAT) | All-in estimate |
|---|---|---|---|
| Single-storey rear | 3m x 5m (15m²) | £48k-£69k | £58k-£83k |
| Side return (infill) | 2m x 8m (16m²) | £51k-£74k | £61k-£88k |
| Loft conversion (dormer) | 25-35m² | £44k-£84k | £52k-£100k |
| Two-storey rear extension | 3m x 5m x 2 (30m²) | £96k-£138k | £115k-£166k |
| Wrap-around (side return + rear) | 35-45m² | £112k-£180k | £134k-£216k |
Source: Derived from Mayfair Studio's London extension costs baseline • Data as of 2026
Professional fees to add
Planning Tips for Southwark
Do not assume conservation area means Article 4
Being in one of Southwark's 48 conservation areas already restricts roof, window and render works nationally, but it does not automatically remove your permitted development rights for a standard rear or side extension. Southwark's own Article 4 directions for extensions are limited to specific small pockets, mainly Sunray Estate and part of Dulwich Wood ward. Check the specific direction that applies to your street rather than assuming from conservation area status alone.
In Dulwich, read the Dulwich SPD alongside the Householder Development SPD
Dulwich is the one part of Southwark with its own dedicated area design guidance. A scheme that would pass easily in Peckham may need more design work in Dulwich to satisfy both documents together. Pre-application advice is worth the fee here.
Do not confuse the HMO Article 4 with a general PD ban
Southwark's Article 4 direction for HMO conversions covers only Henshaw Street SE17 and Bywater Place SE16. If you are simply extending the home you live in anywhere else in the borough, this direction does not apply to you.
Measure from the original rear wall
Many Camberwell and Peckham terraces have a rear outrigger. Permitted development depth is measured from the original rear wall as built, so get a measured survey before assuming a side return infill or rear extension fits within the 3m or 6m limit.
Serve party wall notice early
Almost every extension on a Southwark terrace involves excavating within 3m of a shared party wall. Serve notice at least two months before work starts, and budget for a surveyor on each side of a shared boundary.
Southwark has 48 conservation areas, but its Article 4 direction for HMO conversions covers only Henshaw Street SE17 and Bywater Place SE16, not the whole borough. Most standard house extensions outside a conservation area retain full permitted development rights. Extension costs sit at the London-wide baseline of £3,200-£4,600 per m², with a 5-10% premium in conservation areas. Planning fees are £548 for a householder application and £274 for a Lawful Development Certificate.
Frequently Asked Questions
Does Southwark's Article 4 direction stop me extending my house?
For almost everyone, no. Southwark's Article 4 direction covering HMO conversions applies only to Henshaw Street SE17 and Bywater Place SE16. Two other Article 4 directions, Sunray Estate and part of Dulwich Wood ward (through the Great North Wood direction), require planning permission for development in those specific pockets. Outside these areas, standard permitted development rights for extensions apply, subject to normal conservation area restrictions if your property is in one of Southwark's 48 conservation areas.
How many conservation areas does Southwark have?
48, one of the highest counts of any London borough. They include Dulwich Village, Dulwich Wood, Camberwell Grove, Camberwell Green, Camberwell New Road, Peckham Hill Street, Rye Lane Peckham, Nunhead Cemetery, Nunhead Green, Honor Oak Rise and Walworth Road, among others.
What is the Southwark Plan 2022?
It is Southwark Council's Local Plan, adopted on 23 February 2022 and covering the period 2019 to 2036. It sets the strategic planning policies against which every application in the borough, including householder extensions, is assessed.
What is the Householder Development SPD?
It is Southwark's supplementary planning document giving detailed design guidance for rear, side and roof extensions, adopted by cabinet in July 2025, replacing a 2015 technical update to the borough's residential design standards. For Dulwich properties, it applies alongside the separate Dulwich SPD (2013), which covers East Dulwich, Herne Hill, Dulwich Village and a small area west of Peckham Rye.
Do I need planning permission in Dulwich conservation areas?
Almost always, if the extension is visible from the street, affects the roofline, or involves materials that do not match the existing house. Dulwich Village and Dulwich Wood are conservation areas, and Dulwich additionally has its own SPD giving detailed area-specific design guidance. A separate, smaller Sunray Estate Article 4 direction covers a distinct pocket in north Dulwich requiring planning permission for development. Pre-application advice is strongly recommended for any Dulwich extension.
How much does a house extension cost in Southwark in 2026?
All figures inc VAT: a 3m×5m single-storey rear extension costs £58k-£83k all-in. A side return costs £61k-£88k. A loft conversion costs £52k-£100k. A two-storey rear extension costs £115k-£166k. Add 5-10% for work in one of Southwark's 48 conservation areas. These figures are derived by applying the London-wide baseline rate of £3,200-£4,600 per m² directly, since Southwark carries no borough discount or premium in our costs model.
How long does planning permission take in Southwark?
Southwark targets 8 weeks for householder applications. Conservation area applications in Dulwich and Camberwell typically take 10-13 weeks, reflecting closer design scrutiny and the frequency of requested amendments.
Do flats have permitted development rights in Southwark?
No. Permitted development rights for extensions apply only to houses, not flats, under national planning rules. Any external works to a flat in Southwark, including a rear extension to a ground floor flat with its own garden, require a full planning application, plus a licence to alter from the freeholder if the flat is leasehold.
Summary
Southwark's reputation as a difficult borough for extensions is only half right. It has more conservation areas than almost anywhere else in London, and Dulwich carries its own dedicated design guidance on top of the borough-wide Householder Development SPD. But its Article 4 coverage is genuinely narrow: the HMO direction touches two streets, and the general Article 4 pockets sit in specific corners of Dulwich, not across the borough.
For most homeowners in Camberwell, Peckham, Nunhead, Walworth and the wider Old Kent Road area, standard permitted development rights apply, and a well-designed scheme within those limits avoids a planning application altogether. In Dulwich, budget more time for pre-application advice and expect closer scrutiny of materials and scale.
The first step for any Southwark extension project is the same regardless of area: confirm conservation area status, check whether an Article 4 pocket applies to your specific street, and establish which SPDs the council will assess your scheme against.