Garden room vs extension: cost compared
A garden room is much cheaper than an extension: typically about £16,000, against roughly £40,000 to £64,000 for a 20 m² single-storey extension before fit-out. A garden room is ideal for a home office or studio and usually needs no planning permission, but it sits separate from the house and does not add habitable floor area. An extension adds integrated living space and typically more value.
Garden room vs House extension: the cost
| Option | Range | Typical | Priced |
|---|---|---|---|
| Garden room | £8,000 to £30,000 | £16,000 | installed |
| 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.
Garden room vs House extension: the difference
| Factor | How they compare |
|---|---|
| Typical cost | Garden room about £16,000 installed; extension about £2,000 to £3,200 per m² (a 20 m² build is about £40,000 to £64,000). |
| What you gain | Garden room: a separate insulated space in the garden, great for working from home. Extension: extra connected living space inside the house. |
| Planning and value | Most garden rooms are permitted development and quick to install. An extension is a bigger project but usually adds more to the property value. |
| Best for | Garden room: an affordable home office or studio. Extension: more everyday living space and added value. |
Common questions
Yes. A typical garden room is around £16,000 installed, while a single-storey extension of similar floor area usually costs £40,000 or more before any kitchen or bathroom fit-out.
Generally less. A garden room adds useful space and can help a sale, but it is not counted as habitable floor area, so it tends to add less value than an extension that enlarges the house itself.
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.