Rear extension in Sutton
Do you need planning permission for a rear extension in Sutton?
Outside the conservation areas, much of Sutton's suburban stock keeps permitted development rights for a single-storey rear extension within the limits, or larger via prior approval, to the Design of Residential Extensions SPD. Inside a conservation area, expect a full application. The borough-wide small-HMO conversion direction (in force from 22 February 2025) does not itself remove ordinary rear-extension rights.
Generous suburban plots in Sutton, Cheam and Carshalton extend under PD; the Sutton Garden Suburb and village conservation areas need a full application.
Sutton is a leafy outer-south borough of Victorian, Edwardian and interwar streets from Sutton and Cheam to Carshalton, Wallington and Worcester Park. Generous plots with side access make rear extensions a staple outside the protected set pieces. The Design of Residential Extensions SPD sets scale, materials, daylight and neighbour expectations for applications that need permission.
What actually applies in Sutton
Conservation areas in Sutton
Real · planning.data.gov.uk15 designated areas are recorded in the official dataset for this borough without published names. The area report still checks an address against their real boundaries — see the council's own conservation-area and Article 4 pages for the named schedules.
Source: planning.data.gov.uk · Open Government Licence · 15 recorded.
Article 4 directions in Sutton
Real · planning.data.gov.ukNo Article 4 geometry for Sutton appears in the national planning.data.gov.uk dataset, but the borough operates a borough-wide HMO Article 4 direction (made February 2024, in force from 22 February 2025) removing the right to convert a house to a small HMO, plus householder directions in its conservation areas. The Design of Residential Extensions SPD sets householder design expectations. Check the council's Article 4 register for the position at a specific address.
Source: planning.data.gov.uk · Open Government Licence. Checked at address level by the area report.
Prices: HM Land Registry UK House Price Index, December 2025 · 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 Sutton, 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 Sutton?
| 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 Sutton
National geometry does not currently hold Sutton's Article 4 directions — confirm the small-HMO and conservation-area positions on the council's pages. Daylight and party wall issues remain routine hold-ups.
Postcode districts in Sutton
SM1 covers Sutton town centre and Benhilton, the borough's busiest district.
SM1 — Sutton & Benhilton →SM5 is Carshalton — the historic village around its ponds and the All Saints area, a conservation set piece with close design control.
SM5 — Carshalton →SM2 takes in Belmont and the Edwardian Sutton Garden Suburb, a planned cottage estate with conservation protection.
SM2 — Belmont & Sutton Garden Suburb →SM3 is Cheam and North Cheam — the Cheam Village conservation area and the Nonsuch Park fringe.
SM3 — Cheam & North Cheam →SM6 covers Wallington and Beddington — the Beddington Park and church area among the borough's conservation set pieces.
SM6 — Wallington & Beddington →Rear extension in Sutton, asked straight
Do I need planning permission for a rear extension in Sutton?
How much does a rear extension cost in Sutton?
Does the February 2025 small-HMO conversion direction affect rear extensions?
What does the Design of Residential Extensions SPD cover?
Do I need a party wall agreement?
What applies at your address?
Borough-level rules only narrow it down. Enter a Sutton postcode for the live constraint check — conservation area, Article 4 and sold-price comparables, cited to source.
Need it in writing for one address? A planning permission report for a Sutton property — from £59, or surveyor-reviewed from £295.
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.