Free tools
Price it, check it, then build it.
Three calculators for a line-by-line estimate, and two checks to run before you commit. Nothing you enter leaves your device.
Extension cost calculator
Typically £44,400 to £87,500 all-in
Open calculator →Loft conversion cost calculator
Typically £35,000 to £95,900 all-in
Open calculator →Garden room cost calculator
Typically £16,500 to £41,100 all-in
Open calculator →Before you commit
England
Permitted development checker
Find out in two minutes whether your extension, loft or garden room is likely to need planning permission, and why.
Check my project →Got a quote?Builder quote checker
See how a quote compares with a QS estimate for the same job, what it leaves out, and which terms to question.
Check a quote →