Devizes, Wiltshire
Semi-detached rear extension in Devizes
Single or two-storey extensions for semi-detached houses, with side access and one party wall. If you live in Devizes and want to know what a semi-detached rear extension would cost and whether it needs planning, start with the online guide price or a free site visit.
We cover Devizes (SN10) as part of our Wiltshire work. Semi-detached houses are common across Wiltshire, and their side access makes rear extensions quicker to build.
Book a free site visit
Tell us about the house and we'll call to arrange a free, no-obligation visit.
How much does a semi-detached rear extension cost in Devizes?
In Devizes, our guide for a semi-detached rear extension is £1,980–£3,220 per square metre including VAT for a standard specification. South West prices run slightly above our West Midlands baseline; natural stone to match the house is the main variable.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £23,500–£38,500 |
| 4 m wide × 5 m deep (20 m²) | £39,500–£64,500 |
| 4 m wide × 6 m deep (24 m²) | £47,500–£77,500 |
Your written price follows a measured survey and an agreed design, so it reflects your house, not an average.
Do you need planning permission for a semi-detached rear extension in Devizes?
Here is how the rules in England apply to a semi-detached rear extension in Devizes.
English permitted development (Class A) allows a single-storey rear extension of 3 metres on a terraced or semi-detached house and 4 metres on a detached one, measured from the original house, with a maximum height of 4 metres and eaves of no more than 3 metres within 2 metres of a boundary.
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.
If 3 or 4 metres is not enough, England's prior approval route allows 6 metres on a terraced or semi-detached house and 8 metres on a detached house for a single-storey rear extension. Neighbours are consulted, the council decides within 42 days, and the fee is £249, rising to £310 from 8 December 2026.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent. Before any drawing we look up the property's history with the council, because earlier extensions and removed rights change the answer.
What are homes in Devizes like to extend?
Stone-built and rendered houses are common around Devizes, so matching the walling is a design decision in its own right: natural stone, reconstituted stone or a render finish across old and new.
How a semi-detached rear extension in Devizes comes together
Free site visit
We measure the house and garden, look at the back wall, drainage and boundaries, and talk through what you want from the space.
Design and guide price
Two or three layout options with a guide price for each, so you choose the design knowing what it costs.
Planning and regulations
We take the design through the right planning route, then produce the construction drawings and engineer's calculations for building control.
Fixed price and build
A written price for the agreed design, a start date and a named contact through the build, ending with the building control completion certificate.
Semi-detached rear extensions near Devizes
We also build rear extensions for semi-detached houses in nearby Calne (6.1 miles) and Melksham (6.5 miles).
- Semi-detached rear extension in Calne
- Semi-detached rear extension in Melksham
- Semi-detached rear extension in Chippenham
- Semi-detached rear extension in Trowbridge
- Semi-detached rear extension in Neston
Other work in Devizes:
FAQ
Semi-detached rear extension questions in Devizes
Can I get a price without a visit?
Our online guide-price tool gives a range in a couple of minutes. A written price needs a survey.
How long does a rear extension take to build in Devizes?
Most single-storey rear extensions take 10 to 16 weeks on site and two-storey extensions 16 to 26 weeks, after design and approvals.
Single or two-storey on a semi?
Two-storey if you need bedrooms, single-storey if you need a bigger kitchen. Planning risk is lower for single-storey.
How much does a semi-detached rear extension cost in Devizes?
As a guide, £1,980–£3,220 per square metre including VAT for a standard specification. For example, 3 m wide × 4 m deep (12 m²): about £23,500–£38,500 at that rate. Your written price follows the survey.
Do I need planning permission for a rear extension in Devizes?
Often not for a single-storey rear extension of up to 3 metres (4 metres on a detached house) under permitted development, or up to 6 or 8 metres with prior approval, unless the house is in a conservation area or its rights have been removed.
Is the site visit in Devizes free?
Yes. We visit, measure up and talk through the options with no cost and no obligation.