TL;DR — Key Facts
- Build cost per sqm: £2,200 – £3,200 (outer London borough)
- Council planning fee: £548 (householder application, 2026)
- Typical projects: rear extension, side-return, two-storey, wraparound
- Conservation areas: 17 designated areas in Sutton
- Permitted Development: Generally available outside conservation areas
What does Sutton do with an extension application?
Sutton decides quickly and mostly says yes: 86.3% of householder applications approved, 98.6% settled inside eight weeks, and an agreed extension of time on only 13.5% of applications against 34.5% across London. Its Datahub set records 8,137 extension applications at 65% approved.
| Measure | Sutton | London |
|---|---|---|
| Householder approval rate | 86.3% | 83.0% |
| Decided inside eight weeks | 98.6% | — |
| Applications with an agreed extension of time | 13.5% | 34.5% |
| Extension applications in the Datahub | 8,137 | 65% approved |
| Larger-extension prior approvals granted | 34 | 20.6% of those determined |
| Householder planning application fee | £548 | statutory, England 2026 |
Sources: decision figures from MHCLG District Planning Application Statistics (PS1 and PS2), twelve quarters to March 2026; the Datahub row from the Planning London Datahub, retrieved 15 August 2026, phrase-matched and comparable within Sutton only; the fee from the Fees for Applications Regulations 2012 as amended. Build costs on this page are our own 2026 London range, not a published statistic.
What does a Sutton extension cost in 2026?
This is the cost picture. The service page for house extensions in Sutton covers the submission itself.
House extension build costs in Sutton typically range from £2,200 to £3,200 per square metre, reflecting Sutton's position as an outer London borough. These figures cover the construction cost only and do not include professional fees, planning fees, or VAT.
Sutton's stock is consistent enough that quotes here are unusually comparable: interwar semis, similar spans, similar ground. The variable is the width of the opening at the rear and whether the roof is touched. Carshalton's Victorian cottages are the exception, being smaller and older, where tying a new structure into existing walls takes more care and therefore more time.
Typical extension costs in Sutton (build only)
On top of the build cost, you will need architectural drawings. These fees are 30% below typical London architect rates.
What moves the price of a Sutton extension?
Sutton is the most predictable authority in this guide: 98.6% of householder applications decided inside eight weeks, an extension-of-time rate of 13.5%, and thirteen enforcement notices across three years (MHCLG planning statistics, retrieved 1 September 2026). Designation reaches 17 areas, nothing sits under an Article 4 Direction, and the interwar semis come with flank passages. If a Sutton project runs late or over budget, the council will very rarely be the reason.
Conservation areas
Sutton has 17 designated conservation areas, including Carshalton Village, Beddington Park, Cheam Village, Sutton Central. If your property is in a conservation area, Permitted Development rights are restricted, meaning you may need a full planning application (£548 council fee). Conservation area applications also tend to require higher-quality materials and more sympathetic design, which can increase build costs by 10-20%.
Property type
The housing stock in Sutton is predominantly 1930s semi-detached dominates; edwardian terraces and villas in sutton central; victorian cottages in carshalton; post-war in hackbridge. Victorian and Edwardian terraces typically suit side-return and rear extensions, while 1930s semi-detached properties are well suited to two-storey rear extensions. Detached houses offer the most flexibility but often have larger footprints, meaning higher absolute costs even if the per-sqm rate is similar.
Access and logistics
The 1930s stock through Sutton, Cheam, Worcester Park and Hackbridge nearly always has a flank passage, letting machinery round to the garden and keeping excavation costs ordinary. Carshalton's Victorian cottages are the tight exception and sit inside the borough's designated areas. Plots here are generally deep enough that a rear extension leaves usable garden behind it.
Our drawing fees for Sutton extensions
At Architectural Drawings London. No hourly billing, no surprises. Our fees cover everything needed for a valid planning submission to Sutton Council and for building regulations approval.
Drawing fees for extensions in Sutton
Every package includes a measured survey of your existing property, existing floor plans and elevations, proposed floor plans and elevations, a site plan, and a design and access statement where required. Our MCIAT chartered architectural technologists handle the full process from survey to submission, and we liaise with Sutton Council on your behalf.
We cover all Sutton postcodes: SM1, SM2, SM3, SM4, SM5, SM6, SM7.
Planning or permitted development in Sutton?
Many house extensions in Sutton can be built under Permitted Development (PD) rights without needing a planning application. Under PD, single-storey rear extensions can extend up to 6 metres from the original rear wall for terraced and semi-detached houses, or 8 metres for detached houses (under the Prior Approval process).
Sutton has 17 conservation areas, mostly around Carshalton and Cheam, with no Direction under Article 4 anywhere. Across the interwar semis that dominate here, the side-extension prohibition is what designation actually costs an owner. On Carshalton's Victorian cottages, older and more tightly built, the materials and cladding rule is the one that shapes a scheme.
Two-storey extensions almost always require full planning permission. Sutton Council generally expects two-storey extensions to be subordinate to the original dwelling, set in from the side boundary, and designed to avoid unacceptable loss of light or privacy to neighbouring properties.
Sutton granted 972 certificates of lawfulness across three years (MHCLG planning statistics, retrieved 1 September 2026). In a borough with almost no enforcement activity, the certificate's value is deferred rather than immediate - it is the document that answers a purchaser's solicitor in ten years' time about work nobody kept a file on. The council fee is small and the drawings already exist.
Frequently asked questions
How much does a house extension cost in Sutton?
Build costs for a house extension in Sutton typically range from £2,200 to £3,200 per square metre, as Sutton is an outer London borough. A typical single-storey rear extension of 15-20 sqm would cost between £33,000 and £64,000 for the build alone. On top of build costs.
Can I extend under Permitted Development in Sutton?
Many single-storey rear extensions in Sutton qualify as Permitted Development, allowing you to build without planning permission. You can extend up to 6 metres from the rear wall for terraced and semi-detached houses, or up to 8 metres for detached houses under Prior Approval. However, properties in Sutton's 17 conservation areas have more restricted PD rights. We recommend applying for a Lawful Development Certificate (£274) to confirm PD eligibility.
How long does a house extension take in Sutton?
A typical house extension project in Sutton takes 5-8 months from initial instruction to completion. This breaks down as: 2-3 weeks for measured survey and drawing preparation, 8 weeks for planning determination by Sutton Council (if required), 2-4 weeks for building regulations approval, and 8-16 weeks for construction depending on the size and complexity of the extension.
Do I need a Party Wall Agreement for an extension in Sutton?
One adjoining owner on the semi-detached stock. What normally engages the 1996 statute on a rear extension here is the digging: thirty days' warning, rising to sixty where construction sits on the junction line itself. Permitted development status makes no difference: the Act governs the relationship with the neighbour, not with the council.
What experience do you have with extensions in Sutton?
We prepare extension drawings for properties across all Sutton postcodes (SM1, SM2, SM3, SM4, SM5, SM6, SM7). Our MCIAT chartered architectural technologists understand Sutton Council's policies, design guides, and local precedents. We have a council-ready drawing review across all 33 London boroughs.
