The short answer
A garage conversion typically costs around £500–£1,200 per square metre in 2026, depending on the finish and whether the room needs plumbing. A single garage of roughly 13–18m² therefore usually works out at £6,000–£20,000 in total. Per-m² rates are a useful sense-check rather than an exact quote, because fixed costs such as the door infill and building control do not scale neatly with floor area. See the main cost guide for whole-job figures.
Builders and homeowners often talk about garage conversions in pounds per square metre because it makes different-sized garages easier to compare. The rate is a helpful guide, but it is not the whole story: a small garage carries the same fixed costs — the door infill, the survey, building control sign-off — as a slightly larger one, so very small conversions tend to look expensive per m². This guide gives realistic 2026 per-m² ranges by finish level and shows how to use them sensibly. All figures are typical illustrations, not quotes.
Per square metre at a glance
- Basic finish £500–£750/m²
- Standard finish £750–£1,000/m²
- High finish / wet room £1,000–£1,200+/m²
- Single garage area ~13–18m²
- Double garage area ~28–36m²
- Use the rate as a sense-check, not a quote
Per-m² rates by finish level
The per-m² figure mostly reflects how much upgrading the space needs and how it will be finished. A basic conversion — a plastered, decorated room with simple flooring — sits at the lower end. A standard finish with good insulation, electrics, heating and flooring sits in the middle. A high-specification room, or one that needs plumbing and drainage such as a kitchen or en-suite, sits at the top. Use the table below to convert a per-m² rate into a rough total for your garage’s floor area.
| Finish level | Per m² (2026) | Single garage (~15m²) |
|---|---|---|
| Basic | £500–£750 | £7,500–£11,250 |
| Standard | £750–£1,000 | £11,250–£15,000 |
| High / wet room | £1,000–£1,200+ | £15,000–£18,000+ |
How much usable space a garage gives
A typical UK single garage is around 13–18m² of internal floor area, which after insulation and finishing usually gives a usable room of roughly 12–16m² — enough for a single or double bedroom, a home office, a snug or a small kitchen. A double garage of around 28–36m² can make a large reception room or an open-plan kitchen-diner. Because the per-m² rate is applied to the finished area, a larger garage usually has a slightly lower rate as the fixed costs are spread further. See converting into a bedroom and converting into a living room for room-specific figures.
Why the rate is only a sense-check
Per-m² rates work well for comparing similar jobs but break down at the extremes. A very small garage carries fixed costs — the door infill, structural and damp work, building control — that do not shrink with the floor area, so the rate looks high. A garage needing underpinning, a raised floor or extensive damp-proofing will exceed the headline rate. Treat the figure as a starting point, then get an itemised quote after a survey. This is general information; your actual cost depends on your specific garage and the quotes you receive, and the work should be carried out by a garage conversion specialist who handles building control.
Compare garage conversion quotes
A per-m² estimate is a starting point — an itemised quote after a survey is what tells you the real figure. Compare quotes from FMB-registered or building-control-approved specialists in your area.
Frequently asked questions
What is the average cost per square metre for a garage conversion?
Around £500–£1,200 per square metre in 2026, depending on the finish and whether the room needs plumbing. A basic room sits at the lower end; a high-specification or wet room such as a kitchen or en-suite sits at the top. These are typical illustrations, not quotes.
How big is a typical single garage in square metres?
A typical UK single garage is roughly 13–18m² of internal floor area, giving a usable room of around 12–16m² once insulated and finished. A double garage is usually around 28–36m².
Why does a small garage cost more per square metre?
Because fixed costs — the door infill, survey, structural and damp work and building control sign-off — do not shrink with the floor area. Spread over a smaller room, they push the per-m² rate up. Larger garages usually have a lower rate.
Sources & further reading
- Federation of Master Builders (FMB) — garage conversion costs and finding registered builders
- Planning Portal — permitted development for garage conversions
- GOV.UK / Building Regulations Approved Documents L, B and C — insulation, fire and damp standards
- RICS — guidance on home improvement costs and value
This is general information, not advice for your specific property or conversion, and not a quote. Per-m² rates are typical illustrations only. The work should be carried out by an FMB-registered or building-control-approved garage conversion specialist. We are an independent information and introduction service, not a builder.