Garden room cost calculator
Choose a size, your region and a finish for an insulated, wired garden room. Nothing you enter leaves your device.
Single-storey extension
£0
Likely between £0 and £0, including VAT
- Building work
- Fees and permissions
- Contingency
An estimate to plan with, not a quote. Ground conditions, access and your design will move the real price.
How the estimate is worked out
Building work
A 2026 rate per square metre, or a typical price for each type of loft conversion, adjusted for your region and finish, then split into the main parts of the job.
Fees and permissions
Design drawings, a structural engineer, building control and any planning fee, taken as a share of the building work.
Contingency
10% held back for what nobody can see until work starts. Most projects use some of it.
All figures include VAT at 20%. Not included: furniture, appliances, moving out during works, or a party wall surveyor if your neighbours need one.
Getting quotes
How to find a good garden room supplier
A fair price starts with comparing the same job across several firms.
- Ask for three quotes from the same drawings. Without a shared specification, each firm prices a different job.
- Check each firm before you invite it. Look it up at Companies House, ask to see its insurance certificate, and speak to a recent customer. TrustMark, the government-endorsed scheme, lists registered firms.
- Compare what is included, not just the total. Our quote checker shows how a quote compares with our estimate and what it leaves out.