Two-storey side extensions in Corsham
Adding a two-storey side extension in Corsham gives you two new rooms stacked on one footprint. Here's how we'd approach it, what it typically costs and the rules that apply in England.
Useful details for planning a two-storey side extension in Corsham.
- Postcode districts
- SN14
- County / area
- Wiltshire, England
- Price region
- South West England
- Guide price
- £88,500–£119,000 (£2,110–£2,830 per m²)
- Approval route
- Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.
- Nearest towns
- Neston (Wiltshire) (1.7 miles), Chippenham (3.1 miles), Melksham (4.7 miles)
- Distance to Swindon
- about 19.3 miles
- First visit
- Free, no obligation
About a two-storey side extension
A two-storey side extension is a new two-floor addition built into the space beside your house, often over a driveway or side passage. It typically adds one or two bedrooms upstairs and a utility, study or larger kitchen below, without giving up rear garden.
We cover Corsham (SN14) and the places around it, including Neston (Wiltshire) (1.7 miles), Chippenham (3.1 miles) and Melksham.
What it costs in Corsham
Expect a two-storey side extension in Corsham to land somewhere around £88,500–£119,000 for a 3 m × 7 m footprint on two floors (42 m² of new floor space). Our South West England guide rate is £2,110–£2,830 per m², including VAT. Steelwork for wide openings is the item most likely to move the figure; we'll know once the engineer has designed it.
| Spec | Per m² | A 3 m × 7 m footprint on two floors (42 m² of new floor space) |
|---|---|---|
| Essential | £1,940–£2,610 per m² | £81,500–£109,500 |
| Standard | £2,110–£2,830 per m² | £88,500–£119,000 |
| Premium | £2,530–£3,400 per m² | £106,500–£143,000 |
Planning and building regulations in Corsham
In England, a two-storey side extension always needs householder planning permission, because permitted development only allows single-storey extensions beyond a side wall. The fee is £548 (or £575 for applications made from 8 December 2026), and councils should decide within 8 weeks of validation. Expect them to look at set-back, roof height, gaps to the boundary and the effect on neighbours.
Approval in England: Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.
Building regulations: Building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end.
Design points for Corsham homes
Avoiding a terracing effect
Where semi-detached houses sit close together, side extensions on neighbouring houses can join up and turn a row of pairs into a terrace. Many councils ask for a gap to the boundary at first floor to stop this, so we check local guidance before fixing the width.
Matching the ridge and roof
A hipped house usually needs a hipped extension roof, and a gabled house a gable. Matching the pitch, tiles, ridge detail and brick bond is what makes a side extension look original rather than added, and councils look closely at it on a front-facing addition.
How we'd run your project
Visit and first ideas
One of our team visits your house in Corsham, checks the walls, roof and drains, and sketches out options with you.
Design and approvals
We draw the extension and check it against the rules for England, then apply for planning permission or a certificate of lawfulness, whichever fits.
Detail and price
Construction drawings, engineer's calculations and building control sign-off, then a written fixed price for the build.
Finish and certify
Second fix, plastering and making good, then building control's final inspection and the completion paperwork.
Questions about two-storey side extensions in Corsham
How much does a two-storey side extension cost in Corsham?
Our guide for South West England, which covers Corsham, is £2,110–£2,830 per m² including VAT. A typical project with a 3 m × 7 m footprint on two floors (42 m² of new floor space) comes to about £88,500–£119,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.
Who handles building regulations for a project in Corsham?
We handle it as part of the project. What's needed in England: building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end. We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.
Which postcodes do you cover around Corsham?
We cover Corsham (SN14) and nearby places including Neston (Wiltshire), Chippenham and Melksham, plus the rest of Wiltshire. The first site visit is free.
How long does a two-storey side extension take?
Allow 4 to 8 weeks for survey and design, then the approval period (councils should decide householder applications within 8 weeks of validation), then 4 to 8 weeks of technical design, which can overlap. The build itself usually takes 14 to 20 weeks, longer for large or complex designs.
Can I build a two-storey side extension over my driveway?
Yes, if the drive is wide enough for a useful room and the council accepts the design. You may lose off-road parking, which some councils weigh up, and the foundations need to suit the ground below. We check parking, drains and meter positions at the free site visit before any drawings are prepared.
Nearby
The same service in neighbouring towns:
Other extensions in Corsham
- Rear
- Wraparound
- Part two-storey
- Over a garage
- First floor
- Semi-detached
- Detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in Corsham · Two-storey side extensions across Wiltshire
Tell us about your house in Corsham and we'll call you back to arrange a free, no-obligation visit.