A professionally built, fully insulated garden room in the UK typically costs about £1,200 to £2,500 per square metre, with most builds around £1,700 to £2,200. A 10 m² home office is therefore roughly £15,000 to £22,000, and a 20 m² room £22,000 to £35,000.
Electrics, heating, a toilet and groundworks can add to the price, and permitted development rules and building regulations may apply.
Garden room cost estimator
The estimator uses indicative prices from the sources below and does not replace a quote. Prices from suppliers are often for the room only, so check what each quote includes.
Garden room cost by size
Using a typical insulated build at the standard range of £1,700 to £2,200 per square metre:
| Floor area | Typical cost | Typical use |
|---|---|---|
| 6 m² (roughly 2 m by 3 m) | £10,200 to £13,200 | Small home office or studio |
| 10 m² (roughly 3 m by 3.5 m) | £17,000 to £22,000 | Home office |
| 15 m² (roughly 3 m by 5 m) | £25,500 to £33,000 | Office with meeting space or gym |
| 20 m² (roughly 4 m by 5 m) | £34,000 to £44,000 | Larger studio or guest room |
| 30 m² (roughly 5 m by 6 m) | £51,000 to £66,000 | Large garden room or annexe-style space |
Published guides cover a wider range, from £1,200 to £2,500 per square metre. Some suppliers quote £15,000 to £22,000 for a 10 m² office, and £22,000 to £35,000 for a 20 m² room.
Typical garden room cost at a glance
Typical total for a standard insulated build by floor area.
What pushes the cost up or down
- Size: bigger rooms cost more in total but usually less per square metre.
- Specification: insulation, glazing, cladding and roof covering all change the price.
- Foundations: ground screws, concrete bases and sloping sites affect cost.
- Services: electrics, heating, data and plumbing can add thousands.
- Access: restricted access increases labour and delivery cost.
- Location: London and the South East are higher.
Costs people forget
| Item | Typical allowance |
|---|---|
| Structural engineer calculations | £500 to £1,500 |
| Party wall agreement, if near a boundary | £700 to £1,500 per neighbour |
| Planning application, if required | £528 in England |
| Building control, if required | Several hundred pounds |
| Electrics and consumer unit work | Needs a Part P registered electrician |
| Landscaping and path | Often not included |
Planning permission and building regulations depend on the size, height, location and use. A self-contained annexe where someone lives usually needs planning permission. See our garden studio planning guide and outbuildings planning guide.
Before you ask for quotes
Decide what the room is for, how you will heat and power it, and where the cable and drainage will run. A garden office and a guest room need very different specifications.
Ask each supplier whether the price includes the base, delivery, electrics and VAT.
Planning permission and building regulations
Many detached garden rooms are permitted development in England if they meet the conditions: they are single storey, stay below the maximum height (2.5 metres if within 2 metres of a boundary), are behind the front of the house, cover no more than half the garden, and are not used as separate living accommodation. Listed buildings, conservation areas and some houses have restricted rights.
Building regulations normally do not apply to a detached single-storey building under 15 square metres with no sleeping accommodation, and a building of 15 to 30 square metres is also exempt if it is at least 1 metre from the boundary or built substantially of non-combustible materials. Larger rooms, rooms used for sleeping, and those with toilets or kitchens usually need approval. Always check with your local planning authority and the permitted development checker.
Cutting the cost without cutting corners
- Keep the room modest, because every extra square metre adds cost.
- Choose a straightforward cladding and roof covering.
- Run electrics and drainage the shortest sensible distance from the house.
- Compare at least three itemised quotes, including those from local builders as well as specialist suppliers.
- Check a base with the concrete foundations calculator if you plan a concrete slab.
Sources and further reading
- BestBuilders: garden room cost UK Per square metre ranges for 2026
- Checkatrade: garden room cost guide Typical costs by size
- MyBuilder: garden room cost Price guide for garden rooms
- Planning Portal: outbuildings Permitted development rules for outbuildings
External links open in a new tab. Costs combine several published price guides, which differ. Last checked November 2026.
Frequently asked questions
How much does a garden room cost in the UK?
A professionally built, fully insulated garden room typically costs about 1,200 to 2,500 pounds per square metre, with most between 1,700 and 2,200 pounds. A 10 square metre office is roughly 15,000 to 22,000 pounds.
Do I need planning permission for a garden room?
Many detached garden rooms are permitted development in England if they meet size, height and use conditions. A self-contained annexe usually needs planning permission, and listed buildings and conservation areas have extra rules.
Do I need building regulations for a garden room?
Usually not for a small detached building under 15 square metres with no sleeping accommodation, and not for one of 15 to 30 square metres if it is 1 metre from the boundary or built of non-combustible materials. Larger or residential rooms generally need approval.
How long does it take to build a garden room?
A prefabricated garden room can take a few days to a few weeks on site. A bespoke build takes longer.
Can I live in a garden room?
A room used as a separate home normally needs planning permission and full building regulations approval. A home office or hobby room does not.