Garage conversion vs extension: which costs less?
Converting a garage is far cheaper than building an extension: typically about £14,000, against roughly £40,000 to £64,000 for a 20 m² single-storey extension before fit-out. The garage route reuses space you already have, but you lose the garage and gain a smaller, fixed footprint. An extension adds brand-new floor area and usually more value, for a much larger budget.
Garage conversion vs House extension: the cost
| Option | Range | Typical | Priced |
|---|---|---|---|
| Garage conversion | £7,500 to £20,000 | £14,000 | for the conversion |
| House extension | £2,000 to £3,200 | £2,500 | per m² |
Costwise guide prices, reviewed June 2026, not quotes. Note the two are quoted on different bases, so the figures above are not a like-for-like comparison on their own.
Garage conversion vs House extension: the difference
| Factor | How they compare |
|---|---|
| Typical cost | Garage conversion about £14,000; extension about £2,000 to £3,200 per m² (a 20 m² build is about £40,000 to £64,000). |
| Space and effort | A garage conversion is mostly internal and quicker. An extension is a bigger build but adds new, larger living space. |
| Trade-offs | Converting loses the garage and parking. An extension takes garden space and costs much more. |
| Best for | Garage: the cheapest, fastest way to add a room. Extension: maximum new space and added value. |
Common questions
Converting a garage is much cheaper, typically around £14,000, versus £40,000 or more for a single-storey extension of similar size, because the garage already has walls, a roof and a floor.
Usually less. An extension adds new floor area and tends to add more value, while a garage conversion adds usable space at lower cost but can reduce appeal where buyers expect a garage.
These are independent guide prices based on typical UK jobs in 2026. Your actual cost depends on your property, spec, access and where you live. Always get at least three written quotes before committing.