Extensions in Chiswick: design, planning and build
Planning an extension in Chiswick? Compare extension types, see guide prices adjusted for Chiswick and book a free site visit.
- Postcode districtsSW13, SW14, W3, W4, W6, W12
- Price regionLondon (×1.3)
- Planning rulesEngland
- Site visitFree, no obligation
Planning rules in Chiswick
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 two-storey rear extension is permitted development only if it projects no more than 3 m from the original rear wall, sits at least 7 m from the rear boundary, matches the roof pitch and uses obscure, non-opening side windows upstairs. Most two-storey extensions therefore go through a householder planning application, which costs £548 from 1 April 2026 and normally takes about 8 weeks.
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.
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).
Chiswick and surrounding towns
Across SW13, SW14, W3, W4, W6, W12, we can visit, measure and advise. The same team covers Acton (1 mile), Barnes (1 mile), Shepherds Bush (2 miles), Notting Hill (3 miles), Fulham (3 miles), all within easy reach. Just over the Surrey border, East Molesey is about 8 miles away.
Popular extension prices in Chiswick
Every figure below is a guide for Chiswick, adjusted for London build costs (×1.3) and including VAT. Design and council fees are shown separately on each page.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Single-storey rear extensions | 20 m² | £53,000 – £68,000 |
| Extensions over a garage | 12 m² | £32,500 – £42,500 |
| Wraparound extensions | 25 m² | £74,500 – £94,500 |
| Conservatory replacement extensions | 14 m² | £39,000 – £50,500 |
| Side return extensions | 11 m² | £34,000 – £43,000 |
| Orangery extensions | 16 m² | £58,000 – £73,000 |
| Kitchen extensions | 20 m² | £54,500 – £69,000 |
Which extension suits a Chiswick home?
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.
The types we would usually look at first for a home in Chiswick are side return extensions, glass box extensions and kitchen extensions, depending on the garden and how the house is laid out.
Every extension type in Chiswick
- Annexe extensions · from £71,500
- Home office extensions · from £20,500
- Planning permission for extensions · from £450
- Building regulations for extensions · from £1,150
- Utility and boot room extensions · from £18,000
- Timber frame extensions · from £27,000
- Double-storey extensions · from £49,000
- Bungalow extensions · from £34,000
- Kitchen extensions · from £35,000
- Side extensions · from £28,500
- Single-storey rear extensions · from £27,000
- Extension plans and drawings · from £1,550
- Orangery extensions · from £39,000
- Side return extensions · from £23,000
- Glass box extensions · from £39,000
- Wraparound extensions · from £46,500
- Flat roof extensions · from £27,000
- Porch extensions · from £5,200
- Conservatory replacement extensions · from £26,000
- Pitched roof extensions · from £28,500
- Bedroom extensions · from £33,500
- Extensions over a garage · from £31,000
Free site visit
It starts with a visit to your house to measure, check access and talk through ideas and budget.
Design and approvals
We produce the drawings and structural design, and manage the approvals so they are in place before work starts.
Fixed written price
With the design and specification agreed, you get a fixed written price and a start date.
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 Chiswick
How much does an extension cost in Chiswick?
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.
How long does an extension take in Chiswick?
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 cover all of Chiswick?
Yes, including the surrounding parts of Greater London. Site visits are free and there is no obligation.
Will my neighbours need to be told?
If you apply for planning or prior approval the council notifies them, and in England party wall notices may be needed for work near a shared boundary.
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 Chiswick
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.