Side extensions in Darwen: design, approvals and build
Planning a side extension in Darwen? We survey the house, work out the planning route, draw the design and build it, so you deal with one team from the first visit to the completion certificate.
- Guide price in DarwenFrom £20,500 inc VAT
- PlanningSingle storey can be permitted development
- Build time10–18 weeks on site
- Postcode districtsBB3
Extensions in and around Darwen
Our survey diary covers Darwen, including BB3. Nearby, we also take on projects in Blackburn (4 miles), Accrington (6 miles), Chorley (7 miles), Rawtenstall (7 miles).
Horwich, in Greater Manchester, is roughly 8 miles from Darwen and also on our list. The North West has a high share of Victorian and Edwardian terraces with rear yards and outriggers, plus large areas of inter-war semis in the suburbs.
Planning and approvals in Darwen
In England a single-storey side extension can be permitted development if it is no more than 4 m high and no wider than half the width of the original house. Two-storey side extensions, and any side extension on designated land such as a conservation area, need a householder planning application.
The planning position for a specific Darwen address depends on its history and any designations, which is why we check it at the first visit.
If the work involves a shared wall, building on the boundary, or digging foundations within 3 m (sometimes 6 m) of a neighbour's building, the Party Wall etc. Act 1996 applies and notice must be served before work starts: two months for work to a party wall, one month for new walls on the boundary and for excavations.
Applications are decided by the local planning authority (your district, borough or unitary council).
Who a side extension suits
- Detached and semi-detached houses with side land
- Houses where the rear garden is small
- Homes needing a utility, study or ground-floor bedroom
Side extension prices in Darwen
Prices below are for Darwen, using the North West England factor of ×0.95. They are guide ranges including VAT for the build only, not a quote.
Typical rates in Darwen: £1,660 to £3,230 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| 2.5 m × 5 m 12 m² | £20,500 – £25,500 | £23,000 – £30,500 | £29,500 – £39,000 |
| 3 m × 6 m 18 m² | £29,500 – £36,000 | £35,000 – £45,500 | £44,000 – £58,500 |
| 3 m × 8 m 24 m² | £39,500 – £48,000 | £46,500 – £60,500 | £59,000 – £78,000 |
For a figure based on your own dimensions, use our guide-price tool.
Our process, step by step
Site visits are free and there is no obligation. Where drawings are needed, the design stage is priced in writing before it starts.
Free site visit
A designer visits, takes measurements and photos, and discusses layouts, budget and timing with you.
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
The price is fixed in writing once the design is settled, with a clear programme and payment stages.
Build and sign-off
The build is managed from start to finish, inspected at each stage and signed off on completion.
Side extension questions answered
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Darwen, and the guide-price tool gives a range for your own size. After the survey you get a written price before anything is agreed.
Do you cover all of Darwen?
Yes. We cover Darwen and the surrounding parts of Lancashire. Site visits are free and there is no obligation.
Do I need building regulations approval in Darwen?
Yes. Almost every extension needs it, whatever the planning route. We prepare the drawings and book the inspections.
Can I build over my driveway?
Yes, if the foundations work and you keep any parking the council requires. Drains and services under drives are common, so we check before design.
How much does a side extension cost?
Our guide range is about £1,660 to £3,230 per m² including VAT, depending on specification, so a standard 18 m² single-storey side extension lands around £35,000 to £45,500 in Darwen.
Book a free site visit in Darwen
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.