Extensions over a garage in Winchester
Our extensions over a garage service in Winchester covers everything: measured survey, design, planning or permitted development checks, structural design, building control and the build itself.
Winchester: the key facts for this kind of project.
- Postcode districts
- SO21, SO22, SO23 and SO24
- County / area
- Hampshire, 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
- Bishopstoke (6.8 miles), Eastleigh (6.9 miles), Fair Oak (7.1 miles)
- Distance to Southampton
- about 11.7 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.
We cover postcode districts SO21, SO22, SO23 and SO24 in and around Winchester, along with neighbouring Bishopstoke, Eastleigh and Fair Oak.
What it costs in Winchester
Our guide for South East England is £1,930–£2,800 per m² including VAT. On a project with 3 m × 6 m of new first-floor space (18 m²), that puts an extension over a garage in Winchester at roughly £34,500–£50,500. 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 | 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 Winchester
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 Winchester homes
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.
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.
How we'd run your project
Understand the brief
At your home in Winchester we agree what you need: bedroom count, bathroom, kitchen space, and how much garden you want to keep.
Choose the approval route
Some designs fit permitted development, most need a householder application. We decide which applies in England before drawing in detail.
Detail and price
Construction drawings, engineer's calculations and building control sign-off, then a written fixed price for the build.
Build it
The new structure goes up first, then we open into the house, finish inside and get the completion certificate.
Questions about extensions over a garage in Winchester
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 planning permission for an extension over a garage in Winchester?
Winchester 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 Winchester?
We cover Winchester (SO21, SO22, SO23 and SO24) and nearby places including Bishopstoke, Eastleigh and Fair Oak, plus the rest of Hampshire. The first site visit is free.
Can my garage take a room on top?
Sometimes, but it needs checking. Many garages are built on shallow footings with thin walls, designed only for a single storey. We dig a trial hole and inspect the walls, and the structural engineer decides whether to reuse them, strengthen them, underpin the footings or build new foundations inside the garage.
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.
Nearby
Nearby towns we cover for extensions over a garage:
Other extensions in Winchester
- Rear
- Side
- Wraparound
- Part two-storey
- First floor
- Semi-detached
- Detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in Winchester · Extensions over a garage across Hampshire
Tell us about your house in Winchester and we'll call you back to arrange a free, no-obligation visit.