Wraparound extensions in Isleworth: design, approvals and build
Isleworth homeowners can use us for the whole wraparound extension project: survey, design, planning or permitted development checks, building regulations and the build itself.
- Guide price in IsleworthFrom £46,500 inc VAT
- PlanningUsually a householder application
- Build time14–20 weeks on site
- Postcode districtsTW1, TW3, TW4, TW5, TW7
Will the council need to approve it?
In England a wraparound extension is assessed as both a side and a rear extension, and the combination usually falls outside permitted development, so most need a householder planning application (£548 from 1 April 2026).
Homes in conservation areas, national parks, National Landscapes (formerly AONBs), the Broads and World Heritage Sites have tighter rules, so we always check the property's status and planning history before design starts.
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.
Building regulations approval is separate from planning. In England you can use the council's building control team or a registered building control approver; a full plans application gets the drawings checked before work starts, and the inspector signs the work off with a completion certificate.
Applications are decided by the local planning authority (your district, borough or unitary council).
Extensions in and around Isleworth
Our survey diary covers Isleworth, including TW1, TW3, TW4, TW5, TW7, TW8. Neighbouring towns we cover include Hounslow (1 mile), Heston (2 miles), Richmond (2 miles), Southall (3 miles).
Just over the Surrey border, East Molesey is about 5 miles away. London's housing is dominated by Victorian and Edwardian terraces, many with a rear outrigger and a side return, and 1930s semis in the outer boroughs. Conservation areas are common, so the planning check comes first.
Is a wraparound extension right for your house?
- Semi-detached houses with a side passage
- Terraced houses that want the largest ground floor possible
- Families who want kitchen, dining and living in one space
Guide prices for Isleworth
Labour and material costs vary across the UK, so for Isleworth we use our London factor (×1.3). The ranges include VAT and exclude design, structural and council fees.
Typical rates in Isleworth: £2,600 to £4,810 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| Compact L-shape 18 m² | £46,500 – £56,500 | £53,500 – £68,000 | £67,500 – £87,000 |
| Medium L-shape 25 m² | £65,000 – £78,000 | £74,500 – £94,500 | £94,000 – £120,500 |
| Large L-shape 32 m² | £83,000 – £100,000 | £95,500 – £121,000 | £120,500 – £154,000 |
For a figure based on your own dimensions, use our guide-price tool.
How the project works
Site visits are free and there is no obligation. Where drawings are needed, the design stage is priced in writing before it starts.
Free site visit
We visit your Isleworth home, measure up, talk through what you want and check the planning position.
Design and approvals
Drawings are prepared and agreed with you, then submitted for the right planning route and building regulations approval.
Fixed written price
You receive a written, itemised price and programme. Nothing starts until you are happy with it.
Build and sign-off
Work is carried out to the agreed programme, inspected by building control and signed off at the end.
Common questions in Isleworth
Do I need building regulations approval in Isleworth?
Yes. Almost every extension needs it, whatever the planning route. We prepare the drawings and book the inspections.
Who do I contract with for a wraparound extension in Isleworth?
Your contract is with S&K Property Investments and Improvement Ltd, which designs and manages the project and the build teams who carry it out.
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Isleworth, and the guide-price tool gives a range for your own size. After the survey you get a written price before anything is agreed.
Will I need to move a drain?
Often. Side returns frequently contain a manhole or a shared drain. Building near or over a public sewer needs the water company’s consent in England and Wales, which we arrange.
Do wraparound extensions need planning permission?
Usually, yes. In England the side element counts as a side extension and the rear element as a rear extension, and the combination normally falls outside permitted development. A householder application costs £548 in England from 1 April 2026.
Book a free site visit in Isleworth
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.