Brentwood, Essex
Semi-detached rear extension in Brentwood
For homes in Brentwood, a semi-detached rear extension is often the simplest way to gain space without moving. Single or two-storey extensions for semi-detached houses, with side access and one party wall. We take it from survey to completion certificate.
Brentwood is covered from our Essex round, including CM13, CM14 and CM15. In Brentwood we measure the attached neighbour's extension at the survey, because it often sets the sensible depth for yours.
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 Brentwood?
A semi-detached rear extension in Brentwood is priced at £2,010–£3,290 per square metre including VAT as a guide, before kitchen fit-out and fees. East of England prices run slightly above our West Midlands baseline; clay soils near trees are the main foundation variable.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £24,000–£39,500 |
| 4 m wide × 5 m deep (20 m²) | £40,500–£65,500 |
| 4 m wide × 6 m deep (24 m²) | £48,500–£79,000 |
Ground conditions, glazing, the roof and how far the house is opened up move the final figure within the range.
Do you need planning permission for a semi-detached rear extension in Brentwood?
The planning route for a semi-detached rear extension in Brentwood is set by England's householder rules and your council.
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's rules allow a rear extension of more than one storey without an application only when it is no deeper than 3 metres and at least 7 metres from the boundary opposite the rear wall, and never on designated land. Most two-storey schemes need householder planning permission.
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. We check your house's planning history and any conservation area before drawing, so the route is clear before you spend on plans.
What are homes in Brentwood like to extend?
Brentwood mixes Victorian terraces with 1930s semis, so both side returns and full-width kitchen extensions suit houses here.
How a semi-detached rear extension in Brentwood comes together
Survey visit
We visit free of charge, measure up, check access, drainage and neighbours' extensions, and note what you want the room to do.
Drawings and budget
Floor plans and elevations for the options, each with a guide price.
Planning and regulations
We take the design through the right planning route, then produce the construction drawings and engineer's calculations for building control.
Written price, then build
Once the design and approvals are in place, you get a fixed written price and programme, and we build through to sign-off.
Semi-detached rear extensions near Brentwood
Neighbouring places we cover include Harold Wood (3.6 miles) and Emerson Park (4.5 miles).
- Semi-detached rear extension in Harold Wood
- Semi-detached rear extension in Emerson Park
- Semi-detached rear extension in Billericay
- Semi-detached rear extension in Upminster
- Semi-detached rear extension in Hornchurch
Other work in Brentwood:
FAQ
Semi-detached rear extension questions in Brentwood
Can I live at home while the extension is built?
Usually yes. Most of the work is outside until the back wall is opened near the end, and that stage is screened off.
What postcode areas do you cover around Brentwood?
Including CM13, CM14 and CM15, and the surrounding Essex area.
Do I need a party wall agreement?
Usually with the attached neighbour, in England and Wales.
Who will build my extension?
Vetted building teams working under contract to us. Your contract is with S&K Property Investments and Improvement Ltd for the design and the build.
Is the site visit in Brentwood free?
Yes. We visit, measure up and talk through the options with no cost and no obligation.
Do I need planning permission for a rear extension in Brentwood?
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.