Extensions over a garage in Rottingdean

Quick reference for homeowners in Rottingdean.

Postcode districts: BN2
County / area: East Sussex, England
Price region: South East England
Guide price: £34,500–£50,500 (£1,930–£2,800 per m²)
Approval route: Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.
Nearest towns: Peacehaven (2.6 miles), Brighton (3.7 miles), Hove (4.9 miles)
Distance to Brighton: about 3.7 miles
First visit: Free, no obligation

About an extension over a garage

An extension over a garage is a new first-floor room built on top of an existing attached garage, usually a bedroom, en-suite or study. It uses a footprint you already have, so it adds floor space without taking any garden. The garage walls and foundations often need strengthening or replacing to carry the new floor.

Around Rottingdean we also work in Peacehaven, Brighton and Hove, and across the rest of East Sussex. Postcode district in and near Rottingdean: BN2.

What it costs in Rottingdean

In South East England, which includes Rottingdean, we'd expect an extension over a garage to cost around £34,500–£50,500 for 3 m × 6 m of new first-floor space (18 m²), or £1,930–£2,800 per m² including VAT. We'll give you a written design-stage price first, then a fixed build price once the drawings are agreed.

Spec	Per m²	3 m × 6 m of new first-floor space (18 m²)
Essential	£1,770–£2,580 per m²	£32,000–£46,500
Standard	£1,930–£2,800 per m²	£34,500–£50,500
Premium	£2,310–£3,370 per m²	£41,500–£60,500

Planning and building regulations in Rottingdean

In England, most garages sit beside the house, so building over one makes a two-storey extension beyond a side wall, which always needs planning permission. If the garage is at the rear, the 3 m and 7 m rules for two-storey rear extensions apply, measured from the original house. A householder application costs £548 (or £575 for applications made from 8 December 2026).

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 Rottingdean homes

Floor levels and headroom

Garage floors are often lower than the house, and the new first floor may not line up with the existing landing. We set the floor level to avoid awkward steps upstairs, while keeping enough headroom in the garage below for a car or storage.

Garage walls and the door opening

Garage walls are often a single skin of brick or block with piers, and the wide door opening needs a beam over it. Many over-garage extensions need new inner walls or a steel frame to carry the floor and to insulate properly, which we confirm before the design is fixed.

How we'd run your project

Measure and listen
A visit to Rottingdean to understand how you live in the house now and what the extra rooms need to do, plus a first look at the structure.
Get it approved
Once you're happy with the design we submit it to the council for Rottingdean and deal with any questions from the planning officer.
Fixed price in writing
With approved drawings and calculations, we give you a fixed build price and a programme you can plan around.
Build
Foundations, walls, floor, roof, windows, then first and second fix. We break through into the house as late as we can.

Questions about extensions over a garage in Rottingdean

Do I need planning permission for an extension over a garage in Rottingdean?

Rottingdean 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.

Which postcodes do you cover around Rottingdean?

We cover Rottingdean (BN2) and nearby places including Peacehaven, Brighton and Hove, plus the rest of East Sussex. The first site visit is free.

How long does an extension over a garage 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.

Do I need to convert the garage as well?

No. You can keep the garage for parking or storage and build only the room above, as long as the floor between them and any door into the house meet fire separation rules. Converting the garage at the same time is often good value, because the walls and foundations may be upgraded anyway.

Can I add an en-suite above the garage?

Yes, and it is a common choice for a main bedroom. The en-suite needs an extract fan under Part F, a route for the soil pipe down to the drains and enough fall for the waste, which can be harder over a garage. We plan the pipe route through the garage or an outside wall early.

Nearby

Other towns near Rottingdean:

Other extensions in Rottingdean

All two-storey extension services in Rottingdean · Extensions over a garage across East Sussex

Book a free site visit in Rottingdean and we'll tell you what's possible, what approvals you need and what the design stage would cost.