Two-storey side extensions in Clapham
For a two-storey side extension in Clapham, the first questions are always the same: how big, which approvals, and what it will cost. This page answers all three for Greater London.
Clapham: the key facts for this kind of project.
- Postcode districts
- SW4
- County / area
- Greater London, England
- Price region
- London
- Guide price
- £103,500–£138,500 (£2,460–£3,300 per m²)
- Approval route
- Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.
- Nearest towns
- Brixton Hill (0.9 miles), Balham (1 mile), Battersea (1.2 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 Clapham (SW4) and the places around it, including Brixton Hill (0.9 miles), Balham (1.0 miles) and Battersea.
What it costs in Clapham
In London, which includes Clapham, we'd expect a two-storey side extension to cost around £103,500–£138,500 for a 3 m × 7 m footprint on two floors (42 m² of new floor space), or £2,460–£3,300 per m² including VAT. The fastest way to a firmer number is a free site visit, after which we price the design stage in writing.
| Spec | Per m² | A 3 m × 7 m footprint on two floors (42 m² of new floor space) |
|---|---|---|
| Essential | £2,260–£3,040 per m² | £95,000–£127,500 |
| Standard | £2,460–£3,300 per m² | £103,500–£138,500 |
| Premium | £2,950–£3,960 per m² | £124,000–£166,500 |
Planning and building regulations in Clapham
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 Clapham homes
Side windows, boundaries and gutters
Upstairs windows in the side wall face the neighbour, so they are usually obscure-glazed and fixed, or left out. Building close to the boundary also raises questions about foundations, overhanging gutters and access for maintenance, so we design the eaves and gutter to stay within your land.
Access and services
Side extensions often cover the only route to the back garden, a gas meter, soil pipes or a drain run. We plan bin and bike access, move meters and pipes where needed and check drains early, because these items affect both cost and layout.
How we'd run your project
Start at your house
We come to your home in Clapham, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
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.
Fixed price in writing
With approved drawings and calculations, we give you a fixed build price and a programme you can plan around.
Build and sign-off
Vetted teams working under S&K build the extension, and we arrange the building control completion certificate at the end.
Questions about two-storey side extensions in Clapham
Who handles building regulations for a project in Clapham?
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 Clapham?
We cover Clapham (SW4) and nearby places including Brixton Hill, Balham and Battersea, plus the rest of Greater London. The first site visit is free.
Do I need planning permission for a two-storey side extension in Clapham?
Clapham is in England, so England planning rules apply. Planning permission is needed: in England, permitted development only allows single-storey extensions to the side. If in doubt, a lawful development certificate or a planning application gives you certainty before you build.
How much does a two-storey side extension cost in Clapham?
Our guide for London, which covers Clapham, is £2,460–£3,300 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 £103,500–£138,500. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.
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
Nearby towns we cover for two-storey side extensions:
Other extensions in Clapham
- 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 Clapham · Two-storey side extensions across Greater London
Tell us about your house in Clapham and we'll call you back to arrange a free, no-obligation visit.