Two-storey side extensions in Brighton
Adding a two-storey side extension in Brighton 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.
Before you start in Brighton, here's what applies.
- Postcode districts
- BN1 and BN2
- County / area
- East Sussex, England
- Price region
- South East England
- Guide price
- £94,500–£127,000 (£2,260–£3,030 per m²)
- Approval route
- Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.
- Nearest towns
- Hove (1.2 miles), Portslade (3.5 miles), Rottingdean (3.7 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.
Around Brighton we also work in Hove, Portslade and Rottingdean, and across the rest of East Sussex. Postcode districts in and near Brighton: BN1 and BN2.
What it costs in Brighton
A guide price for Brighton: around £94,500–£127,000 for a 3 m × 7 m footprint on two floors (42 m² of new floor space). That works out at £2,260–£3,030 per m² of new floor space, including VAT at 20%. Design fees, structural calculations and approval fees are separate and listed on our prices page.
| Spec | Per m² | A 3 m × 7 m footprint on two floors (42 m² of new floor space) |
|---|---|---|
| Essential | £2,070–£2,780 per m² | £87,000–£117,000 |
| Standard | £2,260–£3,030 per m² | £94,500–£127,000 |
| Premium | £2,710–£3,630 per m² | £113,500–£152,500 |
Planning and building regulations in Brighton
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 Brighton homes
Set-down and set-back
Councils usually want a two-storey side extension to look subordinate to the house. Setting the front wall back from the main front and dropping the ridge slightly below the main roof helps it read as an addition, and is often expected in local design guidance.
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
Free site visit
We visit your home in Brighton, look at the structure, access and boundaries, and talk through what you want the new rooms to do.
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.
Engineer it
Foundations sized for two floors, steels for any openings, and building control approval, all before anyone starts on site.
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 Brighton
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.
Who handles building regulations for a project in Brighton?
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.
Do I need planning permission for a two-storey side extension in Brighton?
Brighton 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 Brighton?
Our guide for South East England, which covers Brighton, is £2,260–£3,030 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 £94,500–£127,000. 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 Brighton
- 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 Brighton · Two-storey side extensions across East Sussex
Want a figure first? Try our guide price tool, then book a free visit to firm it up.