Garage Conversion Cost in Southampton: A Typical Project
Garage conversion cost in Southampton is usually the first thing people ask us about once they've admitted the garage is full of bikes, paint tins and boxes rather than a car. So instead of another page of national averages, this is how a typical single integral garage conversion runs when we take one on, from the first survey visit to the completion certificate, with what each stage tends to cost in 2026.
The example is a composite of the jobs we see most around Bitterne, Shirley and Bassett, and out towards Chandler's Ford and Hedge End: a 1970s or 80s semi with a single garage built into the side of the house, roughly 2.5m by 5m, being turned into a home office or a downstairs bedroom.
Starting with the survey visit
We always survey before quoting, and with garages it matters more than usual. A garage was built to keep a car dry, not to be lived in, so the floor normally sits lower than the hall, the walls are often single-skin brick and any damp-proof membrane is likely to be thin or missing. On the visit we're checking:
How far the garage floor sits below the house floor, which decides how much we need to raise it
Whether the brickwork above the garage door sits on a sound lintel or needs a new one
Where the nearest heating pipework and consumer unit are
Whether the planning history of the house removed permitted development rights
That last one catches a lot of people out. Plenty of the estates built around Southampton from the 1980s onwards came with planning conditions requiring garages to stay as parking. If yours has one, you'll need a planning application before any work starts, so we look into it up front rather than finding out halfway through.
What a single garage conversion costs in Southampton
For a straightforward single integral garage conversion into a habitable room (insulated, plastered, heated and signed off by building control) our customers in Southampton are typically looking at £13,000 to £19,000. Add a shower room or en suite and it rises to around £20,000 to £30,000, mostly because of the drainage and plumbing runs.
Roughly how the main elements of the basic version break down:
Taking out the garage door and building the new wall with a window: £1,800 to £3,600
Raising and insulating the floor, with a damp-proof membrane and screed: £1,400 to £2,900
Electrics, including sockets, lighting, a data point and certification: £1,100 to £2,000
Insulating and plastering the walls and ceiling, then decorating: £1,200 to £2,400
Heating, usually extending the radiator circuit or fitting electric underfloor heating: £700 to £1,700
The rest of the total covers the things cost-guide lists tend to leave out: skips, protecting the rest of the house while we work, structural calculations if the lintel needs replacing, project management and a sensible contingency. A detached garage at the bottom of the garden costs more again, as it usually needs its own power supply and sometimes a new drainage run. For the Dorset side of things, our guide to garage conversions in Weymouth covers the same job further west.
How long it takes, week by week
On site, a typical single conversion takes three to five weeks. It usually goes something like this:
Week one: garage door out, footings checked, new wall and window built so the room is weathertight early on.
Week two: floor raised and insulated, first-fix electrics and heating pipework in, wall insulation started.
Week three: plastering, then the floor finish once the screed is dry enough.
Weeks four and five: second-fix electrics, heating connected, skirting, internal door, decoration and the building control completion visit.
Most people carry on living at home as normal. The noisiest days are the first few, when the door comes out and the brickwork goes up. Drying time for plaster and screed is what stretches a programme, particularly in a cold, damp Hampshire winter, so for a January start we'd allow an extra week.
Planning permission and building regulations
Converting an integral garage doesn't usually need planning permission, as long as the work is internal and you're not extending the house. The exceptions are those estate planning conditions, listed buildings, and conservation areas such as Southampton's Old Town, where changing the front of the building can need consent.
Building regulations are a different story. You will always need building regs approval, because you're turning a non-habitable space into a habitable room. Building control will want to see the floor and wall insulation, the lintel or new foundations, ventilation, fire safety (escape matters if it's a bedroom) and an electrical certificate. We deal with the building control notice and the inspections as part of the job, and you get the completion certificate at the end, which your solicitor will ask for when you sell.
Is converting your garage worth it?
For most of the Southampton homes we work on, yes, as long as you don't actually need the garage for a car. You get a proper extra room for less than a typical extension, without losing any garden and usually without a planning application. It works particularly well as a home office, a playroom or a ground-floor bedroom for an older relative. It's less of a win if the house would lose its only off-road parking on a street where spaces are already tight, and we'll be honest with you about that on the survey visit.
Because we handle the electrics, heating and plumbing in-house, adding an en suite or underfloor heating doesn't mean waiting around for a separate firm to fit you in.
Related reading
Get a clear price for your garage conversion
If you're in Southampton, Eastleigh, Totton or nearby and your garage has quietly become a storage unit, we'd be glad to come and have a look. We'll measure up, check the floor levels and the planning history, and give you a clear written price with each stage set out. Book a survey visit at completebuilds.co.uk and tell us a little about the garage and what you'd like it to become.
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