Chelmsford, Essex
Single-storey rear extension in Chelmsford
Single-storey rear extension in Chelmsford: ground-floor space across the back of the house, usually for a kitchen, dining or family room. We measure the house, show you what the rules allow, price it in writing and build it.
We cover Chelmsford (CM1) as part of our Essex work. A depth of 3 to 4 metres keeps many single-storey rear extensions in Chelmsford within permitted development, subject to the house's planning history.
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 single-storey rear extension cost in Chelmsford?
For Chelmsford we work from the East of England rate: £2,010–£3,290 per square metre of new floor, including VAT, standard specification. 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 |
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 single-storey rear extension in Chelmsford?
Whether your single-storey rear extension in Chelmsford needs a planning application depends on its size, your house and any local restrictions.
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.
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 Chelmsford like to extend?
Chelmsford mixes Victorian terraces with 1930s semis, so both side returns and full-width kitchen extensions suit houses here.
How a single-storey rear extension in Chelmsford comes together
Look round and measure
A free visit to see the back of the house, measure it, check the drains and boundaries and hear what you need.
Options and costs
We draw layout options and price each one, so the budget shapes the design rather than surprising you later.
Paperwork handled
Planning, prior approval or permitted development, Building Regulations approval, structural design and party wall notices are all handled by us.
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.
Single-storey rear extensions near Chelmsford
Neighbouring places we cover include Billericay (7.7 miles) and Witham (8.5 miles).
- Single-storey rear extension in Billericay
- Single-storey rear extension in Witham
- Single-storey rear extension in Maldon
- Single-storey rear extension in Wickford
- Single-storey rear extension in Braintree
Other work in Chelmsford:
FAQ
Single-storey rear extension questions in Chelmsford
Do I need planning permission for a rear extension in Chelmsford?
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.
Do I need a party wall agreement?
In England, usually yes if the extension is on or near a shared boundary or the foundations are close to a neighbour's building. We serve the notices.
Will the extension make the room behind it dark?
Not if it is designed well. Rooflights or a lantern over the old back room, and a wide opening into it, keep daylight reaching the middle of the house.
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 Chelmsford free?
Yes. We visit, measure up and talk through the options with no cost and no obligation.
What postcode areas do you cover around Chelmsford?
Including CM1, and the surrounding Essex area.