Extensions in Chelmsford: design, planning and build
More space without moving: we plan and build extensions across Chelmsford, with one team for the drawings, the council and the build.
- Postcode districtsCM1, CM2
- Price regionEast of England (×1.06)
- Planning rulesEngland
- Site visitFree, no obligation
Chelmsford extension prices at a glance
Every figure below is a guide for Chelmsford, adjusted for East of England build costs (×1.06) 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 | £43,000 – £55,500 |
| Side return extensions | 11 m² | £27,500 – £35,000 |
| Extensions over a garage | 12 m² | £26,500 – £34,500 |
| Double-storey extensions | 32 m² | £61,000 – £80,000 |
| Orangery extensions | 16 m² | £47,000 – £59,500 |
| Conservatory replacement extensions | 14 m² | £31,500 – £41,000 |
Choosing the right extension in Chelmsford
The East of England mixes market-town terraces, inter-war semis and modern estates. Clay soils are common in parts of the region, which can affect foundation design.
Depending on the plot, wraparound extensions and bungalow extensions are often the strongest options, with double-storey extensions worth considering where there is room.
Covering Chelmsford and nearby
We cover Chelmsford and the postcode districts CM1, CM2. The same team covers Billericay (8 miles), Witham (9 miles), Maldon (9 miles), Wickford (9 miles), Braintree (10 miles), all within easy reach. For homes towards Hertfordshire, Bishop's Stortford is around 16 miles away.
Do extensions in Chelmsford need planning permission?
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 single-storey side return infill is often permitted development if it stays within the height limits and is no wider than half the width of the original house. Conservation areas, listed buildings and flats always need an application, and the boundary wall usually brings in the Party Wall Act.
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).
All extension types we build in Chelmsford
- Wraparound extensions · from £38,000
- Single-storey rear extensions · from £22,000
- Side extensions · from £23,000
- Planning permission for extensions · from £350
- Timber frame extensions · from £22,000
- Home office extensions · from £16,500
- Porch extensions · from £4,200
- Annexe extensions · from £58,000
- Building regulations for extensions · from £950
- Glass box extensions · from £31,500
- Orangery extensions · from £31,500
- Conservatory replacement extensions · from £21,000
- Flat roof extensions · from £22,000
- Extensions over a garage · from £25,000
- Extension plans and drawings · from £1,250
- Kitchen extensions · from £28,500
- Bedroom extensions · from £27,500
- Utility and boot room extensions · from £14,500
- Side return extensions · from £19,000
- Double-storey extensions · from £40,000
- Pitched roof extensions · from £23,500
- Bungalow extensions · from £27,500
Free site visit
We visit your Chelmsford home, measure up, talk through what you want and check the planning position.
Design and approvals
Once the layout is agreed, we deal with the council: planning permission or written confirmation that none is needed, plus building control.
Fixed written price
We confirm the build price in writing, based on the approved drawings and the finishes you have chosen.
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 Chelmsford
How much does an extension cost in Chelmsford?
Using our East of England factor (×1.06), a standard-spec single-storey extension of 20 m² is a guide £43,000 to £55,500 including VAT, and a 32 m² two-storey extension £61,000 to £80,000. Your written price follows the survey.
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.
Do I need planning permission for an extension in Chelmsford?
Not always. It depends on the size, position and your property's history. Many single-storey rear extensions in England are permitted development or can use prior approval.
Can I get a price before anyone visits?
Yes. This page shows guide prices adjusted for Chelmsford, and the guide-price tool gives a range for your own size and finish in about a minute.
Book a free site visit in Chelmsford
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.