West Sussex
Rear extensions for detached houses in West Sussex
Wider, deeper rear extensions with room for vaulted roofs and big glazing. Across West Sussex we handle the whole rear extension: survey, drawings, the planning route, building control and the build. Towns we cover here include Crawley, Worthing and Bognor Regis.
Detached houses in West Sussex often have room for a deeper rear extension under England's prior approval route or a full-width design. West Sussex has a mix of Victorian terraces near the centre and larger Edwardian and inter-war houses further out. Clay soils across much of the South East mean deeper foundations near trees, which we plan for at the survey.
How much does a detached house rear extension cost in West Sussex?
In West Sussex, our guide for a detached house rear extension is £2,180–£3,580 per square metre including VAT for a standard specification. South East prices run above our West Midlands baseline, mainly on labour rates and clay-soil foundations.
| Size | Guide price inc VAT |
|---|---|
| 4 m wide × 6 m deep (24 m²) | £52,500–£86,000 |
| 5 m wide × 8 m deep (40 m²) | £87,500–£143,500 |
These are guide ranges; the written quote after the survey is the figure that counts.
Do you need planning permission in West Sussex?
Under England's householder permitted development rules you can usually add 3 metres at the back of an attached house, or 4 metres on a detached house, without a planning application, as long as the extension stays under 4 metres high and its eaves stay under 3 metres where it is within 2 metres of a boundary.
England also has the larger home extension route: a single-storey rear extension of up to 6 metres on an attached house or 8 metres on a detached house, after prior approval from the council. The council notifies your neighbours and has 42 days to decide; the fee is £249 (£310 for applications made from 8 December 2026). The route is not available on designated land such as conservation areas.
A two-storey rear extension can be permitted development in England only if it projects no more than 3 metres, stays at least 7 metres from the rear boundary, matches the existing roof pitch and has obscure-glazed upper side windows. In practice most double-storey rear extensions go through a householder planning application.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent.
Where in West Sussex do we work?
FAQ
Questions people ask
How deep can I extend a detached house?
4 metres under permitted development in England, or 8 metres with prior approval, outside designated land.
Can I have a vaulted ceiling?
Yes, with a pitched roof and exposed or boxed rafters, subject to the height limits.
Is an oak frame worth it?
It is a premium finish with a long life; it costs more than blockwork with a plain roof.
Do you cover all of West Sussex?
We cover 15 towns and districts in West Sussex, including Crawley, Worthing and Bognor Regis.
Who builds the extension?
Vetted building teams working under contract to us; your contract is with S&K Property Investments and Improvement Ltd.