Rear extension in Kensington and Chelsea
Do you need planning permission for a rear extension in Kensington and Chelsea?
Almost always, yes. Conservation areas cover most of Kensington and Chelsea, and even where the basic single-storey rear allowance would normally survive conservation-area status elsewhere in London, the borough's dozens of property-specific Article 4 directions frequently remove it on a house-by-house basis. Treat a full householder application as the default and confirm the position for your specific address before you commission drawings — two houses on the same terrace can have different permitted development rights.
Conservation coverage and Article 4 directions make a full householder application the default; matching stock brick and lime mortar are expected.
Rear extensions are the most routine project on London's terraced stock, but Kensington and Chelsea applies unusually exacting design scrutiny even to a straightforward single-storey scheme. The borough's period terraces are built in stock brick and stucco, and officers expect new brickwork and pointing to match the host building closely — lime mortar rather than a modern cement mix is a standard expectation here, not an optional upgrade. Because such a large share of the borough's houses are also listed, a rear extension often needs listed building consent running alongside the planning application: a second consent process, with its own drawings and heritage justification, that most other London boroughs don't require for what is otherwise a routine project.
What actually applies in Kensington and Chelsea
Conservation areas in Kensington and Chelsea
Real · planning.data.gov.ukEvery designated conservation area in Kensington and Chelsea from the official dataset — inside one, permitted development narrows and design scrutiny rises.
- Avondale
- Avondale Park Gardens
- Brompton
- Brompton Cemetery
- Chelsea
- Chelsea Estates
- Chelsea Park/Carlyle
- Cheyne
- Colville
- Cornwall
- Courtfield
- De Vere
- Earl's Court Square
- Earl's Court Village
- Edwards Square/Scarsdale & Abingdon
- Hans Town
- Holland Park
- Kensal Green Cemetery
- Kensington
- Kensington Court
- Kensington Palace
- Kensington Square
- Ladbroke
- Lexham
- Lots Village
- Nevern Square
- Norland
- Oxford Gardens
- Pembridge
- Philbeach
- Queen’s Gate
- Royal Hospital
- Sloane Square
- Sloane/Stanley
- Thames
- The Billings
- The Boltons
- The College of St Mark & St John
- Thurloe/Smith's Charity
Source: planning.data.gov.uk · Open Government Licence. Boundaries are checked at address level by the area report.
Article 4 directions in Kensington and Chelsea
Real · planning.data.gov.ukKensington and Chelsea records dozens of Article 4 directions, listed only by number in the national dataset. They remove permitted development rights on specific properties and estates across the borough, working alongside its conservation-area controls and its strict basement regime — Local Plan Policy CL7 and the 2016 Basements SPD (single storey under gardens, no more than 50% of each garden or open part of the site). Use the area report, or the council's Article 4 register, for the direction that applies at a given address.
Source: planning.data.gov.uk · Open Government Licence · 82 directions recorded. Checked at address level by the area report.
Prices: HM Land Registry UK House Price Index, January 2026 · Open Government Licence.
The planning route — PD or permission?
Permitted development (GPDO Class A) covers single-storey rear extensions up to 3m beyond the original rear wall on attached houses and 4m on detached, with a maximum height of 4m. The 'larger home extension' route extends this to 6m/8m through prior approval with neighbour consultation — but that larger route is not available in conservation areas.
In conservation areas, the basic 3m/4m single-storey rear PD allowance usually survives — what conservation-area status removes is side extensions and two-storey rear extensions. An Article 4 direction can remove more, but Camden's directions in Hampstead and Belsize target front-and-side appearance (solar panels, window changes, boundary treatments), not the single-storey rear allowance. Flats have no PD rights at all. Two-storey rear extensions in conservation areas always need full permission.
Practical rule across London: check the address first. If a conservation area or Article 4 direction applies, budget for a full householder application decided on design, neighbour daylight (the 45-degree test) and materials.
Permitted development limits — rear extension
| Single-storey rear depth — attached house | 3m beyond the original rear wall |
| Single-storey rear depth — detached house | 4m beyond the original rear wall |
| Larger extension via prior approval | 6m attached / 8m detached — not in conservation areas |
| Maximum height (single storey) | 4m |
| Two-storey rear in a conservation area | Full planning permission required |
| Flats | No permitted development rights |
Limits summarise the General Permitted Development Order (Schedule 2, Part 1) as it applies in London. In Kensington and Chelsea, a conservation area, Article 4 direction or listed status changes the route — the panels above show what is designated, and the address check confirms what applies at your property.
How much does a rear extension cost in Kensington and Chelsea?
| Cost per m² (low — straightforward site) | £3,000 |
| Cost per m² (expected) | £3,800 |
| Cost per m² (high — conservation spec, hard access) | £4,600+ |
| Typical build cost (12–18m² single storey) | £36,000 – £83,000 |
| Professional fees, surveys, party wall (add) | 10–18% of build |
Indicative London ranges calibrated from real project data. Conservation-area specifications (matching stock brick, lime mortar, bespoke glazing) and restricted rear access are the two biggest cost drivers. VAT not included.
Realistic timeline
| Design and drawings | 4–8 weeks |
| Planning decision (full application) | 8–12 weeks (8-week statutory target) |
| Prior approval route, where available | 42 days |
| Party wall agreements | 4–10 weeks (parallel) |
| Build | 3–5 months |
What catches people out in Kensington and Chelsea
The trap is assuming general conservation-area rules apply and skipping the address check — Kensington and Chelsea's Article 4 directions attach to specific properties and estates rather than applying uniformly across a conservation area, so a neighbour's permitted development position tells you very little about your own. Where the host building is listed, brick, pointing and window detailing get scrutinised as closely as the massing, and a scheme priced without heritage input from the outset is the one that comes back for redesign.
Postcode districts in Kensington and Chelsea
SW3 is the heart of old Chelsea — the Cheyne, Chelsea and Royal Hospital conservation areas run down to the river, with Hans Town reaching into Knightsbridge.
SW3 — Chelsea →SW7 covers the white-stucco terraces of the Brompton, Courtfield, Cornwall and Queen's Gate conservation areas and the museum quarter.
SW7 — South Kensington & Knightsbridge →W8 spans the Kensington, Kensington Palace and De Vere conservation areas and the grand villas around Holland Park.
W8 — Kensington & Holland Park →W11 is the Ladbroke estate's communal-garden squares and the Norland and Pembridge conservation areas — some of London's most recognisable stucco.
W11 — Notting Hill →W10 mixes the Oxford Gardens conservation area, the Kensal Green cemetery setting and Portobello's northern reach.
W10 — North Kensington →SW5 is Earl's Court — mansion blocks, converted terraces and a high share of flats in Kensington and Chelsea.
SW5 — Earl's Court →SW10 covers West Brompton and the World's End area, with Kensington and Chelsea as the primary authority and a Hammersmith and Fulham edge.
SW10 — West Brompton & World's End →Rear extension in Kensington and Chelsea, asked straight
Do I need planning permission for a single-storey rear extension in Kensington and Chelsea?
Will I need listed building consent as well as planning permission?
How much does a rear extension cost in Kensington and Chelsea?
Can I do a two-storey rear extension?
What's the fastest way to check if permitted development applies to my house?
What applies at your address?
Borough-level rules only narrow it down. Enter a Kensington and Chelsea postcode for the live constraint check — conservation area, Article 4 and sold-price comparables, cited to source.
Free, and it stays free — no account, no payment. The check reads official geometry at the property's own coordinates; listed status, lease terms and the state of the building all sit outside it.
Who to talk to about a rear extension in Kensington and Chelsea
A rear extension is a design-and-consent job first: someone has to draw it and take it through Kensington and Chelsea's planning route. The neighbour, condition and party wall side is separate work and a different profession — which is why there are two doors here, not one.
An extension is a design and consent job: the scheme, the planning application or prior approval, then the building-regs package.
- Residential design for extensions, lofts, basements and conversions
- Planning applications, pre-application advice and appeals
- Lawful development certificates
- Building-regulations and technical design drawings
- Conservation-area design and listed building consent applications
Excavating foundations within 3m of a neighbour is notifiable — the surveyor serves the party wall notices.
- Building surveys, RICS home surveys and defect diagnosis
- Party wall matters and awards
- Technical due diligence before a purchase
- Leasehold and major-works advisory (Section 20)
- Dilapidations and building pathology
Both practices are independent and separately regulated — Hampstead Chartered Surveyors & Building Consultancy is an RICS-regulated firm (Firm Reg. 923064); Hampstead Architecture and Planning are ARB-registered architects. We publish no fees for their work: each quotes directly for the job in front of them. Your enquiry goes to the practice you choose — we never pass your details to builders or other third parties.
Planning terms on this page
Conservation Area · Article 4 Direction · Permitted development · Full planning · Prior approval · Party wall · Designated land
Plain-English definitions · full planning glossary →
Planning Permission Checker provides planning and cost intelligence for early feasibility only. It is not legal, planning, valuation, architectural, structural, or surveying advice. All estimates are indicative and must be verified by qualified professionals before purchase, design, planning submission, or construction.
Cost estimates are indicative only — not a quotation. Final price depends on survey, specification, structure, access, party wall matters, VAT, professional fees, and contractor availability.
Planning outcomes are not guaranteed. Local planning authorities make final decisions.