TL;DR — Key Facts
- Build cost per sqm: £2,500 – £3,800 (inner London borough)
- Council planning fee: £548 (householder application, 2026)
- Typical projects: rear extension, side-return, two-storey, wraparound
- Conservation areas: 45 designated areas in Wandsworth
- Permitted Development: Restricted by Article 4 in some areas
What does Wandsworth do with an extension application?
It approves 91.3% of householder applications, the fourth highest rate in London. But it is slower than that suggests: 5.9% of decisions ran past thirteen weeks and 9.4% of all applications were withdrawn before a decision was reached. Its 46 conservation areas cover 1,061 hectares of the borough.
| Measure | Wandsworth | London |
|---|---|---|
| Householder approval rate | 91.3% | 83.0% |
| Decided beyond thirteen weeks | 5.9% | — |
| Applications withdrawn before decision | 9.4% | 7.4% |
| Extension applications in the Datahub | 6,551 | 84% approved |
| Larger-extension prior approvals granted | 31 | 51.7% 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 Wandsworth only; the fee from the Fees for Applications Regulations 2012 as amended, 2026 rate. Build costs on this page are our own 2026 London range, not a published statistic.
What does a Wandsworth extension cost in 2026?
Ready to move from budgeting to drawings?
House extension build costs in Wandsworth typically range from £2,500 to £3,800 per square metre, reflecting Wandsworth's position as an inner London borough. These figures cover the construction cost only and do not include professional fees, planning fees, or VAT.
The side-return extension is the standard project between the commons, and its cost is set by the structural opening and the temporary support needed while it is formed. What tips a Wandsworth scheme upward is the borough's programme rather than its specification - only 85.8% of householder applications are decided inside eight weeks, and a longer run-up carries its own holding costs.
Typical extension costs in Wandsworth (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 Wandsworth extension?
Wandsworth is the archetypal side-return extension borough and its Victorian streets have produced enough of them that the form is well settled. The council approves 91.3% of householder applications but decides only 85.8% inside eight weeks, with 5.9% running past thirteen (MHCLG planning statistics, retrieved 1 September 2026). Expect consent, and expect the programme rather than the outcome to be where the money leaks.
Conservation areas
Wandsworth has 45 designated conservation areas, including Wandsworth Common, Clapham Common West, Tonsley, Magdalen Park, Nightingale Triangle. 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%.
Article 4 Directions
Wandsworth has Article 4 Directions in place. Article 4 for HMO conversions covering the whole borough. Where Article 4 applies, works that would normally be Permitted Development require a full planning application. This adds £548 to the council fee and typically 2-3 months to the project timeline, which can affect overall costs if you are renting alternative accommodation during the build.
Property type
The housing stock in Wandsworth is predominantly extensive victorian terraced streets — the classic london side-return extension opportunity; edwardian villas around the commons; 1930s semi-detached in southfields. 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
Terraces run unbroken between the commons, so the side return is simultaneously the plot and the sole way in, and everything is carried through the hallway until the structural opening exists. Southfields' interwar semis have proper side passages. Because so many neighbouring properties have already been extended, adjoining structures are often recent, which is worth recording in the schedule of condition.
Our drawing fees for Wandsworth extensions
At Architectural Drawings London. No hourly billing, no surprises. Our fees cover everything needed for a valid planning submission to Wandsworth Council and for building regulations approval.
Drawing fees for extensions in Wandsworth
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 Wandsworth Council on your behalf.
We cover all Wandsworth postcodes: SW8, SW11, SW12, SW15, SW17, SW18, SW19.
Planning or permitted development in Wandsworth?
Many house extensions in Wandsworth 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). However, Wandsworth has Article 4 Directions that may remove some PD rights. Article 4 for HMO conversions covering the whole borough.
Wandsworth's 45 conservation areas sit over repeated terraced frontage between the commons, so the side-extension restriction has little to bite on and the materials rule carries the assessment. Rear depth is reduced as well, which matters on plots where the side-return extension is the standard project. An Article 4 Direction removes further rights again.
Two-storey extensions require full permission. Consent is the likelier outcome here than in most of London, but the timetable is not: only 85.8% of householder applications were decided inside eight weeks and 5.9% ran past thirteen (MHCLG planning statistics, retrieved 1 September 2026). On the terraces between the commons the scheme is normally a first floor above the back addition, judged on its effect on the neighbouring rear rooms.
Wandsworth issued 975 certificates of lawful development in three years (MHCLG planning statistics, retrieved 1 September 2026). Coverage from the Article 4 Direction and 45 conservation areas removes the option on a large share of the terraced streets, so establishing early whether your address is inside or outside that coverage decides which route the project takes and what it costs to get consent.
Frequently asked questions
How much does a house extension cost in Wandsworth?
Build costs for a house extension in Wandsworth typically range from £2,500 to £3,800 per square metre, as Wandsworth is an inner London borough. A typical single-storey rear extension of 15-20 sqm would cost between £37,500 and £76,000 for the build alone. On top of build costs.
Can I extend under Permitted Development in Wandsworth?
Wandsworth's 45 conservation areas sit over housing that is largely repeated terraced frontage, so the designation is protecting a pattern and a proposal is judged on whether it disturbs one. Side extensions are rarely the issue on a terrace; materials and the rear roof are. An Article 4 Direction removes further rights, and between them they reach a large share of the borough's streets.
How long does a house extension take in Wandsworth?
A typical house extension project in Wandsworth 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 Wandsworth 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 Wandsworth?
Two adjoining owners on a mid-terrace Wandsworth house. A side-return build engages the line-of-junction provisions on one flank and the excavation provisions on the other, so both parts of the Act are typically live. Neighbours on these streets generally know the process, which tends to speed agreement - but dissent remains a right, and surveyors' fees fall to the building owner.
What experience do you have with extensions in Wandsworth?
We prepare extension drawings for properties across all Wandsworth postcodes (SW8, SW11, SW12, SW15, SW17, SW18, SW19). Our MCIAT chartered architectural technologists understand Wandsworth Council's policies, design guides, and local precedents. We have a council-ready drawing review across all 33 London boroughs.
