Extensions in Barnes: design, planning and build
We design and build house extensions for homes in Barnes and the surrounding Greater London area, with guide prices adjusted for the region.
- Postcode districtsSW13, SW14, SW15, TW9, W4, W6
- Price regionLondon (×1.3)
- Planning rulesEngland
- Site visitFree, no obligation
What extensions cost in Barnes
Prices on this page use our London factor of ×1.3, include VAT at 20% and cover the build; your written price follows a survey and agreed drawings.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Side return extensions | 11 m² | £34,000 – £43,000 |
| Single-storey rear extensions | 20 m² | £53,000 – £68,000 |
| Kitchen extensions | 20 m² | £54,500 – £69,000 |
| Conservatory replacement extensions | 14 m² | £39,000 – £50,500 |
| Extensions over a garage | 12 m² | £32,500 – £42,500 |
Barnes and surrounding towns
We cover Barnes and the postcode districts SW13, SW14, SW15, TW9, W4, W6. The same team covers Chiswick (1 mile), Roehampton (2 miles), Putney (2 miles), Fulham (2 miles), Shepherds Bush (2 miles), all within easy reach. Just over the Surrey border, East Molesey is about 7 miles away.
Approvals for an extension in Barnes
In England a single-storey rear extension can usually go up to 3 m beyond the original rear wall of a semi-detached or terraced house, or 4 m on a detached house, without a planning application, provided it is no more than 4 m high, keeps eaves to 3 m within 2 m of a boundary and, with other buildings, covers no more than half the land around the original house. The larger home extension prior approval scheme raises those depths to 6 m and 8 m, with neighbours notified and a 42-day decision.
In England a single-storey side return infill is often permitted development if it stays within the height limits and is no wider than half the width of the original house. Conservation areas, listed buildings and flats always need an application, and the boundary wall usually brings in the Party Wall Act.
In a conservation area, national park, National Landscape, the Broads or a World Heritage Site the permitted development limits are tighter (no side or two-storey extensions without an application). Listed homes need listed building consent, and if permitted development rights have been removed, any extension needs an application.
If the work involves a shared wall, building on the boundary, or digging foundations within 3 m (sometimes 6 m) of a neighbour's building, the Party Wall etc. Act 1996 applies and notice must be served before work starts: two months for work to a party wall, one month for new walls on the boundary and for excavations.
Applications are decided by the local planning authority (your district, borough or unitary council).
Choosing the right extension in Barnes
In London, space is at a premium and gardens are often short, so side returns, wraparounds and carefully planned rear extensions tend to make the most of every metre.
For many houses here, kitchen extensions, wraparound extensions or side return extensions gives the most useful space for the budget.
All extension types we build in Barnes
- Pitched roof extensions · from £28,500
- Utility and boot room extensions · from £18,000
- Home office extensions · from £20,500
- Planning permission for extensions · from £450
- Single-storey rear extensions · from £27,000
- Annexe extensions · from £71,500
- Extensions over a garage · from £31,000
- Wraparound extensions · from £46,500
- Bedroom extensions · from £33,500
- Kitchen extensions · from £35,000
- Double-storey extensions · from £49,000
- Conservatory replacement extensions · from £26,000
- Glass box extensions · from £39,000
- Side return extensions · from £23,000
- Extension plans and drawings · from £1,550
- Orangery extensions · from £39,000
- Timber frame extensions · from £27,000
- Flat roof extensions · from £27,000
- Side extensions · from £28,500
- Building regulations for extensions · from £1,150
- Porch extensions · from £5,200
- Bungalow extensions · from £34,000
Free site visit
First, a site visit: we look at the house, garden, access and drains and listen to what you need.
Design and approvals
Once the layout is agreed, we deal with the council: planning permission or written confirmation that none is needed, plus building control.
Fixed written price
We confirm the build price in writing, based on the approved drawings and the finishes you have chosen.
Build and sign-off
Work is carried out to the agreed programme, inspected by building control and signed off at the end.
Questions about extensions in Barnes
How much does an extension cost in Barnes?
Using our London factor (×1.3), a standard-spec single-storey extension of 20 m² is a guide £53,000 to £68,000 including VAT, and a 32 m² two-storey extension £74,500 to £98,000. Your written price follows the survey.
Can I get a price before anyone visits?
Yes. This page shows guide prices adjusted for Barnes, and the guide-price tool gives a range for your own size and finish in about a minute.
How long does an extension take in Barnes?
Usually 2 to 4 months of design and approvals, then 10 to 16 weeks on site for a single-storey extension or 16 to 24 weeks for two storeys.
Do you handle building regulations?
Yes. We prepare the drawings and calculations, submit them and book inspections, ending with a completion certificate.
Book a free site visit in Barnes
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.