Garden room cost per m2: what the job involves and who is registered to do it

How garden room cost per m2 works

1. Separate the fixed costs from the ones that scale. Groundworks setup, plant hire, delivery, the electrical supply run and the crew's mobilisation happen once whatever the size. Frames, insulation, cladding, glazing and internal finish scale roughly with the building. Splitting a quote that way tells you far more than any single rate, and it explains why small rooms look expensive per square metre.
2. Watch the perimeter rather than the area. A garden room's cost is closer to its perimeter and its openings than to its floor. A long thin room and a square room of the same area are different amounts of wall, cladding, insulation and corner detail, and the thin one costs more every time.
3. Ask what the rate is quoted against. A rate for a supplied and erected shell is not comparable with a rate for a finished, powered, decorated room. When somebody quotes a per square metre figure, the only useful follow up is what it includes, because the same building can carry two rates that differ by half.
4. Use the rate as a sense check, never as a budget. Per square metre figures are good for spotting a quote that is wildly out of line and bad for setting expectations. Build the budget from the schedule and use the rate afterwards to see whether the shape of the number looks normal.

Insurance and paperwork

Common questions

Why is a small garden room so expensive per square metre?

Because the fixed half of the job does not shrink. The base still has to be dug and poured, the supply still has to be run, the crew still spends the same time getting in and out, and those costs are then divided by a smaller number.

Does a bigger garden room always cost less per square metre?

Up to a point. The rate falls as the fixed costs spread, then it stops falling and can rise again once the building is large enough to need heavier structure, building control involvement, or an access solution such as a crane.

Should I compare suppliers on a per square metre basis?

Only after you have made them quote the same specification and the same inclusions. Otherwise the rate compares two different products and the lower one is usually the one with more left out.

Registered contractors by region

• Registered roofers in the East Midlands postcode area
• Registered roofers in the East of England postcode area
• Registered roofers in the London postcode area
• Registered roofers in the North East postcode area
• Registered roofers in the North West postcode area
• Registered roofers in the Scotland postcode area
• Registered roofers in the South East postcode area
• Registered roofers in the South West postcode area
• Registered roofers in the Wales postcode area
• Registered roofers in the West Midlands postcode area
• Registered roofers in the Yorkshire and The Humber postcode area