Two-storey side extensions in Lewes
Thinking about a two-storey side extension in Lewes? We design it, take it through the approvals it needs and build it, with one team responsible from the first visit to the final certificate.
What we'd confirm first for a project in Lewes.
- Postcode districts
- BN7 and BN8
- 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
- Rottingdean (5.3 miles), Peacehaven (5.7 miles), Newhaven (5.7 miles)
- Distance to Brighton
- about 7.2 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.
Lewes sits about 7.2 miles from Brighton. Closer to home, Rottingdean is 5.3 miles away and Peacehaven 5.7 miles.
What it costs in Lewes
In South East England, which includes Lewes, we'd expect a two-storey side extension to cost around £94,500–£127,000 for a 3 m × 7 m footprint on two floors (42 m² of new floor space), or £2,260–£3,030 per m² including VAT. These are guides, not quotes. Ground conditions, steelwork and access can move the figure either way.
| 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 Lewes
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 Lewes 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.
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
Measure and listen
A visit to Lewes to understand how you live in the house now and what the extra rooms need to do, plus a first look at the structure.
Drawings, then consent
We draw the scheme, check it against the rules in England, and take it through the right consent with the council.
Technical design
We prepare the building regulations drawings, structural calculations and specification so the build price can be fixed.
Build and hand over
We manage the build from groundworks to decoration-ready finish and hand over with the completion paperwork.
Questions about two-storey side extensions in Lewes
Which postcodes do you cover around Lewes?
We cover Lewes (BN7 and BN8) and nearby places including Rottingdean, Peacehaven and Newhaven, plus the rest of East Sussex. 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.
How much does a two-storey side extension cost in Lewes?
Our guide for South East England, which covers Lewes, 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.
Do I need planning permission for a two-storey side extension in Lewes?
Lewes 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.
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 Lewes
- 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 Lewes · Two-storey side extensions across East Sussex
Ready to talk it through? Call us or send the form and we'll arrange a visit to your home in Lewes.