Lewisham Extension Guide 2026: Planning Permission, Costs & Local Rules
Lewisham runs from the Victorian terraces of Brockley and Deptford to the Georgian villas of Blackheath and the 1930s semis of Grove Park - with 29 conservation areas and a borough-wide Article 4 direction on HMOs along the way. Here is what actually applies before you extend.
TL;DR - The Quick Answer
Lewisham has 29 conservation areas covering Brockley, Blackheath, Forest Hill, Ladywell, Telegraph Hill, Deptford and several smaller Victorian streets - most carry an Article 4 direction that removes permitted development for single dwelling houses, so full planning permission is required. Outside these areas, in Lee, Grove Park, and parts of Catford and Sydenham, standard national permitted development rights apply. Lewisham separately has a borough-wide Article 4 direction on HMO conversions (phased 2020 and 2024) that affects turning a house into a small HMO, not standard rear or loft extensions. Extension costs sit at the London-wide average - Mayfair Studio's London costs guide treats Lewisham as a "South London baseline" borough alongside Greenwich and Southwark, with a 10-15% premium in conservation areas. Standard planning applications take 8 weeks; the householder application fee is £548, and a Lawful Development Certificate confirming permitted development rights costs £274.
Lewisham: A Borough of Contrasts
Lewisham sits in south-east London and covers some of the most varied housing stock of any London borough. Brockley, Forest Hill and Honor Oak are dominated by Victorian and Edwardian terraces - long rows of two- and three-storey properties with rear gardens backing onto each other. Deptford and New Cross add a denser, older layer again: Georgian and Victorian streets built up around the historic dockyard and high street, now covered by three separate conservation areas. Blackheath, jointly designated with Greenwich, has a distinctly grander character of Georgian and early Victorian townhouses and villas set around the Heath. Lee, Hither Green and Grove Park shift to 1930s semis and inter-war housing with larger plots and, in many streets, no conservation area constraint at all.
This variety matters when planning an extension, because the rules and the design expectations differ substantially between a Victorian terrace in Brockley and a 1930s semi in Grove Park. Knowing which regime applies to your specific property, not just your general area, is the first step.
Housing character by area
Victorian and Edwardian terraces, largely built as speculative suburbs from the 1870s onward. Some of the borough's most tightly controlled streets sit here, including the Brockley and Forest Hill conservation areas.
Dense Georgian, Victorian and early-20th-century streets around the historic high street and dockyard. Covered by three conservation areas: Deptford Creekside, Deptford High Street and St Paul's, and Deptford Town Hall.
Georgian and early Victorian townhouses and villas around the Heath. Designated jointly with Greenwich in 1968 - the council describes it as London's first conservation area. The grandest and most formally controlled character in the borough.
More suburban 1930s semis and inter-war housing on larger plots. Hither Green in particular falls outside Lewisham's conservation area boundaries, so standard permitted development typically applies, subject to the borough-wide HMO Article 4 direction where relevant.
A mix of Victorian terraces and later infill. Sydenham has its own conservation areas (Sydenham Hill, Sydenham Thorpes), alongside smaller nearby areas including Jews Walk, Perry Fields and Stanstead Grove.
On the numbers behind that variety: Lewisham's median terraced house price sits at £605,000, its median semi-detached price at £720,000, and 47% of Lewisham properties are owned freehold rather than leasehold, meaning a majority of homeowners need a freeholder's consent before they can extend at all. The borough holds 364 listed buildings and roughly 345 Tree Preservation Order zones, both material considerations alongside conservation area status when scoping a scheme. These figures are drawn from our own analysis of HM Land Registry and planning.data.gov.uk data, set out in full in our London borough extension report.
Lewisham Local Plan and Extensions Policy
The Lewisham Local Plan 2020-2040 was adopted on 16 July 2025 and is now the primary planning document for the borough, replacing the previous Core Strategy, Site Allocations Local Plan and Development Management Local Plan. All planning applications are assessed against this plan.
For householder extensions specifically, the key supporting document is the Alterations and Extensions Supplementary Planning Document (SPD), adopted 24 April 2019 (replacing Section 6 of the previous Residential Standards SPD) and read alongside the new Local Plan. It sets out the design principles Lewisham applies to residential extensions, whether permitted development or full planning permission is the relevant route.
Core design principles the SPD is built around
- Subordinate scale: extensions should be visually subordinate to the original building in height, width and massing
- Matching or complementary materials: particularly important in conservation areas, where materials must respect the original building fabric
- Neighbour amenity: extensions must not cause unacceptable loss of light, outlook or privacy to adjoining properties
- Street character: front and side extensions visible from the street should respect the established building line and character of the terrace or road
Lewisham's Article 4 Direction: HMOs, Not Standard Extensions
Separately from its conservation area controls, Lewisham has a borough-wide Article 4 direction targeting HMO conversions, brought in over two phases. It came into force on 7 March 2020 for the southern wards of Bellingham, Downham, Grove Park and Whitefoot, then extended to every remaining ward on 19 January 2024. The direction now covers the whole borough. Full detail on how HMO Article 4 directions work across London, and how Lewisham's compares with neighbouring boroughs, is in our Article 4 HMO borough guide.
The direction removes permitted development rights under Class L of Part 3 of the GPDO 2015, which would otherwise let a homeowner convert a house (Use Class C3) into a small House in Multiple Occupation for three to six unrelated people (Use Class C4) without planning permission.
What this means in practice for extensions
- If you are simply extending or altering the single-family home you live in, this direction does not apply. Standard national permitted development rights for extensions still operate across Lewisham, outside conservation areas
- If you intend to convert a property into a small HMO (3-6 unrelated occupiers) anywhere in the borough, you need full planning permission - permitted development rights for that change of use no longer exist here
- Larger HMOs of 7 or more occupants are always Sui Generis and always need planning permission, in every London borough, regardless of any Article 4 direction
It is a common mix-up to see "Lewisham has an Article 4 direction" and assume it blocks permitted development for extensions generally. It does not: the HMO direction and the property-specific Article 4 directions covering conservation areas (see below) are two separate instruments doing two different jobs. If your project is a rear extension, loft conversion or side infill on a house you will continue to occupy as a single dwelling, the HMO direction is not the constraint to worry about - conservation area status is.
Conservation Areas and Property-Specific Article 4 Directions
Lewisham Council's planning pages list 29 conservation areas. In most of them the council has also applied a separate Article 4 direction that removes permitted development rights for single dwelling houses - covering external changes visible from public viewpoints, including windows, doors, roofing, porches, boundary treatments, hard surfacing and painting. Commercial properties and flats do not carry permitted development rights in the first place, so these directions are specifically aimed at houses.
Blackheath Conservation Area
The Blackheath Conservation Area was designated jointly with Greenwich in 1968 - the council's own description calls it London's first conservation area. It straddles the Lewisham and Greenwich boundary; the Lewisham portion is determined by Lewisham Council, and Greenwich handles applications on its side. Article 4 protection here is applied through several named sub-areas - Belmont, Collins Street, 52 Lee Terrace and Quentin Road - rather than a single direction covering the whole conservation area.
Blackheath has a grander, more formal character than Brockley: Georgian and Victorian villas set around the Heath, with consistent fenestration, proportions and materials. Extensions here face strict design scrutiny and are almost always confined to the rear.
Brockley Conservation Area
The Brockley Conservation Area was designated in 1973 and covers a wide swathe of Victorian terraced streets. The council describes it as "a leafy speculatively-developed Victorian suburb," with stucco capitals and window surrounds, terracotta details, tile paths and spacious front gardens contributing to a varied but consistent character. An Article 4 direction covers the area, aimed at encouraging the retention of these features - the replacement of original windows and doors, or alterations to roofing and boundary treatments, all require planning permission rather than proceeding under permitted development.
Rear extensions in Brockley are generally assessed on design quality rather than blocked outright: Lewisham officers are typically supportive of good contemporary design at the rear, where it is not visible from the street, provided materials and scale respect the host building.
Telegraph Hill, Forest Hill and Ladywell
Telegraph Hill, straddling New Cross and Hatcham, is one of the areas with its own Article 4 direction protecting a compact grid of Victorian terraces on the hill between New Cross and Brockley. Forest Hill Conservation Area covers a diverse mix of Victorian and Edwardian building types, with an Article 4 direction across the whole area - meaning even small rear extensions that would otherwise be permitted development need an application. Ladywell, with its tight Victorian terracing and an Article 4 direction of its own, typically sees rear extensions and loft conversions rather than side extensions, given the constrained plot widths.
Deptford: three conservation areas, one Article 4 direction
Deptford has three separate conservation areas - Deptford Creekside, Deptford High Street and St Paul's, and Deptford Town Hall - reflecting its history as one of London's oldest dockside settlements. Of the three, only Deptford High Street and St Paul's carries an additional Article 4 direction (made 30 November 2021); Deptford Creekside and Deptford Town Hall are covered by standard conservation area controls without a further Article 4 withdrawal of permitted development rights.
| Conservation area | Character | Article 4? |
|---|---|---|
| Blackheath | Georgian/Victorian villas, joint with Greenwich (1968) | Yes (named sub-areas) |
| Brockley | Victorian terraces, stucco and terracotta detailing (1973) | Yes |
| Telegraph Hill | Victorian terraces, New Cross/Hatcham | Yes |
| Forest Hill | Victorian/Edwardian, varied | Yes (whole area) |
| Ladywell | Victorian terraces, tight plots | Yes |
| Deptford High Street and St Paul’s | Historic high street and dockside | Yes (30.11.2021) |
| Deptford Creekside / Deptford Town Hall | Dockside and civic buildings | No additional direction |
Source: Lewisham Council (lewisham.gov.uk) • Data as of July 2026
Outside these 29 areas, standard permitted development rights for extensions apply across most of Lewisham. Conservation area boundaries can run down the middle of a street, so always verify the status of your specific property with Lewisham Planning, or with our free AI checker, before assuming permitted development rights apply.
Permitted Development for Lewisham's Victorian Terraces
Where Article 4 directions do not apply - primarily the more suburban streets of Lee, Grove Park, Hither Green and parts of Catford and Sydenham - the standard national permitted development rules for householders apply in full.
| Extension type | PD limit | Prior approval limit |
|---|---|---|
| Single-storey rear (terraced/semi) | 3m depth | Up to 6m |
| Single-storey rear (detached) | 4m depth | Up to 8m |
| 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 |
Two features of Lewisham's Victorian terraces come up repeatedly when applying these limits: rear outriggers and side returns. Many bay-fronted terraces in Brockley, Forest Hill, New Cross and Telegraph Hill were built with a single-storey rear outrigger, a closet wing running alongside the main rear elevation, leaving a narrow side return alongside it. Because permitted development depth is measured from the original rear wall of the house as it stood on 1 July 1948 (or as built, if later), an existing outrigger changes where that 3m or 6m measurement starts. Our dedicated guides to side return extensions and Victorian house extensions cover this in detail.
Key restrictions to know
- Properties in any of Lewisham's 29 conservation areas lose most permitted development rights, and most also carry an additional Article 4 direction
- Listed buildings always require listed building consent in addition to any planning permission
- Tree Preservation Orders are common across Lewisham - check before any groundworks or excavation near trees
Before relying on PD rights, confirm your property is not in one of Lewisham's 29 conservation areas and check whether a property-specific Article 4 direction applies. Our free AI checker looks up your address against these designations in seconds.
Planning Applications in Lewisham
Standard householder planning applications in Lewisham are decided within 8 weeks from validation; major applications take up to 13 weeks. The great majority of householder extensions are decided by officers under delegated powers rather than going to planning committee.
Application process
Extension Costs in Lewisham 2026
Against our borough-wide benchmark of London extension costs in 2026 (£3,200-£4,600 per m²), our costs guide treats Lewisham as a "South London baseline" borough alongside Greenwich and Southwark - meaning no borough-specific premium or discount, just the general London-wide range. The figures below are modelled from that per-m² baseline, not independent Lewisham-specific project data, and all include VAT at 20%.
| Extension type | Typical size | Construction cost (inc VAT) | All-in estimate |
|---|---|---|---|
| Rear extension (single-storey) | 3m × 5m (15m²) | £46k–£70k | £55k–£84k |
| Side return (infill) | 2m × 8m (16m²) | £40k–£63k | £48k–£76k |
| Loft conversion (dormer) | 25–35m² | £47k–£73k | £56k–£88k |
| Two-storey rear extension | 3m × 5m × 2 (30m²) | £79k–£120k | £95k–£145k |
| Wraparound (rear + side return) | 25–35m² | £71k–£108k | £85k–£130k |
Conservation area premium: add 10-15% in Brockley, Blackheath, Forest Hill, Ladywell, Telegraph Hill and Deptford for matching materials, heritage-profile windows and additional design scrutiny.
| Extension type | Typical size | Construction cost (inc VAT) | All-in estimate |
|---|---|---|---|
| Rear extension (single-storey) | 3m x 5m (15m²) | £46k-£70k | £55k-£84k |
| Side return (infill) | 2m x 8m (16m²) | £40k-£63k | £48k-£76k |
| Loft conversion (dormer) | 25-35m² | £47k-£73k | £56k-£88k |
| Two-storey rear extension | 3m x 5m x 2 (30m²) | £79k-£120k | £95k-£145k |
| Wraparound (rear + side return) | 25-35m² | £71k-£108k | £85k-£130k |
Source: Mayfair Studio cost model, derived from London extension costs 2026 • Data as of 2026
Professional and statutory fees to add
Common Extension Types by Area
Brockley, Telegraph Hill and Honor Oak: rear extensions and lofts
The long, narrow terraced properties here lend themselves naturally to rear extensions and loft conversions. A single-storey rear extension into the garden, typically 3-4m deep with a flat or lean-to roof and a large glazed opening, is the most common project. Dormer loft conversions adding a bedroom and bathroom are the second most frequent. Side return extensions, infilling the narrow alley between the house and boundary wall, are also common where the side passage runs the full depth of the ground floor.
Blackheath: strict rear-only design
Extensions in Blackheath are almost always to the rear; the formal front elevations of Georgian and Victorian properties are not candidates for alteration. Rear extensions are typically single-storey with flat or shallow-pitched roofs, set below the original eaves line. Officers are attentive to materials, though good contemporary design can still be approved where it is clearly of high quality.
Deptford and New Cross: mixed terraces and civic buildings
Deptford's three conservation areas cover a mix of residential streets and historic civic and dockside buildings. Rear extensions and side returns on the terraced housing stock follow the same design principles as Brockley - subordinate scale, matching materials - but expect closer scrutiny where a property sits close to Deptford High Street and St Paul's, which carries its own Article 4 direction on top of standard conservation area controls.
Lee, Hither Green and Grove Park: 1930s semis
Outside the conservation areas, these streets offer more flexibility. The larger plots associated with 1930s semis typically allow for more substantial rear extensions, and the absence of Article 4 directions across most of this area means permitted development rights often apply. Single-storey rear extensions up to 4m deep may proceed without planning permission on detached properties, subject to standard height and materials conditions.
Catford and Sydenham: mixed terraces, occasional constraint
Catford is largely outside Lewisham's conservation area boundaries, so standard permitted development often applies to its Victorian and later terraces, subject to the usual outrigger and side-return measurement issues. Sydenham is more mixed: its own conservation areas (Sydenham Hill, Sydenham Thorpes) carry Article 4 directions, while streets outside them, and the smaller nearby areas of Jews Walk, Perry Fields and Stanstead Grove, follow the pattern set out above depending on which side of the boundary a property sits.
Planning Tips for Lewisham
Do not confuse the HMO Article 4 direction with a PD ban on extensions
Lewisham's borough-wide Article 4 direction (phased 2020 and 2024) targets HMO conversions under Class L, not standard house extensions. If you are simply extending the home you live in, check conservation area status rather than assuming this direction blocks you.
Use pre-application advice in any of the 29 conservation areas
Given how many Lewisham conservation areas carry an additional Article 4 direction, submitting without pre-application guidance risks a refusal on materials or scale. Officer feedback before you commission drawings is worth the fee, especially in Brockley, Blackheath, Forest Hill and Telegraph Hill.
Blackheath: check which borough applies
If your property sits in the Greenwich portion of the Blackheath Conservation Area, your application goes to Greenwich Council, not Lewisham. The two councils apply similar conservation area policy, but the officers and fee schedules differ.
Never assume permitted development without checking
Even outside the 29 named conservation areas, individual streets and properties in Lewisham carry their own Article 4 directions or Tree Preservation Orders. Use Lewisham's online planning map or our free checker to verify your specific address before starting design.
Serve party wall notice early
Lewisham's Victorian terraces invariably have shared party walls. Serve notice on adjoining owners at least two months before any excavation or structural work, and budget for a party wall surveyor on each side of a shared boundary.
A single-storey rear extension in Lewisham costs £46k-£70k for construction inc VAT, or £55k-£84k all-in. Lewisham has 29 conservation areas, most carrying an additional Article 4 direction that removes permitted development for houses, and a separate borough-wide Article 4 direction on HMO conversions phased in over 2020 and 2024. Standard planning applications take 8 weeks; the householder application fee is £548.
Frequently Asked Questions
Do I need planning permission for a house extension in Lewisham?
It depends on your location. If your property is in one of Lewisham's 29 conservation areas - which include Brockley, Blackheath, Forest Hill, Ladywell, Telegraph Hill and Deptford - most carry an additional Article 4 direction, and you will need full planning permission. Outside these areas, in Lee, Grove Park, Hither Green and parts of Catford and Sydenham, national permitted development rights typically apply for a single-storey rear extension up to 3m (terraced/semi) or 4m (detached).
Does Lewisham's Article 4 direction stop me extending my house?
Not on its own. Lewisham's borough-wide Article 4 direction, phased in on 7 March 2020 (Bellingham, Downham, Grove Park and Whitefoot wards) and 19 January 2024 (all remaining wards), removes permitted development rights for converting a house into a small HMO (Use Class C4). It does not affect standard rear, side or loft extensions to a single-family home. Separately, most of Lewisham's conservation areas carry their own property-specific Article 4 directions covering windows, doors, roofs and boundary treatments - that is the direction that affects a typical extension project.
How many conservation areas are there in Lewisham?
Lewisham Council's planning pages list 29 conservation areas, including Blackheath (designated jointly with Greenwich in 1968, described by the council as London's first conservation area), Brockley (1973), Forest Hill, Ladywell, Telegraph Hill, and three separate conservation areas covering Deptford (Deptford Creekside, Deptford High Street and St Paul's, and Deptford Town Hall). Most carry an additional Article 4 direction removing permitted development for houses.
Is Blackheath in Lewisham or Greenwich?
The Blackheath Conservation Area was designated jointly by both boroughs in 1968. Your planning application goes to the council that covers your specific property - Lewisham Council's planning department for the Lewisham portion, Greenwich for the Greenwich portion. Check your address against each council's planning map.
How much does a rear extension cost in Lewisham in 2026?
A standard single-storey rear extension (3m x 5m, 15m²) costs £46k-£70k for construction inc VAT, or £55k-£84k all-in including design, structural engineering, building control and party wall costs. In Brockley, Blackheath, Forest Hill, Telegraph Hill or Deptford conservation areas, add 10-15% for heritage-matching materials and additional design scrutiny. These figures are modelled from our London-wide costs guide, which treats Lewisham as a South London baseline borough with no premium or discount against the £3,200-£4,600 per m² London average.
How long does planning permission take in Lewisham?
Standard householder planning applications in Lewisham are decided within 8 weeks from validation. Major applications take up to 13 weeks. The householder application fee is £548, and a Lawful Development Certificate confirming permitted development rights costs £274. Conservation area applications can take slightly longer due to additional design scrutiny.
What is the Lewisham Local Plan and does it affect extensions?
The Lewisham Local Plan 2020-2040 was adopted on 16 July 2025 and is now the borough's primary planning document, replacing the Core Strategy, Site Allocations Local Plan and Development Management Local Plan. For householder extensions specifically, the operative document is the Alterations and Extensions SPD, adopted 24 April 2019, which is read alongside the new Local Plan and sets out design expectations on scale, materials, neighbour amenity and street character.
Do I need a party wall agreement for an extension in Lewisham?
Almost certainly yes. The Party Wall Act 1996 applies whenever you excavate foundations within 3m of a neighbouring structure, which covers the vast majority of extensions on Lewisham's terraced streets in Brockley, Deptford, Forest Hill and Telegraph Hill. Serve notice at least two months before work starts and budget £800-£1,400 per adjoining neighbour for surveyor fees.
Can I convert my Lewisham house into an HMO without planning permission?
No. Lewisham's borough-wide Article 4 direction removed permitted development rights for converting a house into a small HMO (3-6 unrelated occupiers) across the whole borough - the direction came into force for Bellingham, Downham, Grove Park and Whitefoot wards on 7 March 2020, then for every remaining ward on 19 January 2024. Full planning permission is required for this change of use anywhere in Lewisham, regardless of which ward the property is in.
Summary
For most Lewisham homeowners - in Lee, Grove Park, Hither Green, Catford or parts of Sydenham - the planning landscape is more straightforward than the borough's 29 conservation areas might suggest. Standard permitted development rights apply outside those areas, the Alterations and Extensions SPD gives clear design principles, and construction costs sit at the London-wide average rather than carrying a premium.
The genuine exceptions are the conservation areas - Brockley, Blackheath, Forest Hill, Ladywell, Telegraph Hill, and Deptford's three - where full planning permission and heritage-sensitive materials are required, most under an additional Article 4 direction. The borough-wide HMO Article 4 direction, phased in across 2020 and 2024, is a separate matter entirely and only affects converting a house into a small HMO, not extending the home you live in.
The first step for any Lewisham extension project is confirming your planning status: conservation area, property-specific Article 4, listed building, or none of the above. That single check determines your route and your realistic timeline.