What will your extension cost?
Answer six quick questions and see a guide price for your extension straight away. Then one checked local builder calls you with an exact quote.
- Free, with no obligation to go ahead
- One builder contacts you, not a crowd
- Single-storey, side return, kitchen, wraparound and two-storey
Get your estimate
Takes about 60 seconds.
How it works
You stay in control at every step.
Tell us about the project
Type, rough size, timing and budget. No drawings needed.
See your guide price
You get a typical price range for your type and size of extension as soon as you finish.
A local builder calls you
We pass your details to one checked builder near you, who visits and gives you an exact quote.
Typical extension costs in 2026
Guide prices for the whole project, excluding VAT. Finish, glazing and ground conditions move the final price, which is why a site visit matters.
Ranges compiled from published 2026 UK cost guides, including Checkatrade and MyJobQuote. They're a starting point, not a quote.
Common questions
Do I need planning permission?
Often not for a single-storey rear extension, which can fall under permitted development if it stays within set limits on depth and height. Side return, wraparound and two-storey extensions usually need a planning application. Your builder or your local council will confirm for your house.
How long does an extension take?
A single-storey extension usually takes around 8 to 16 weeks on site. Larger two-storey or wraparound projects take longer. Design and any planning come before that.
Who are you?
Extension Check is an independent introduction service, not a building company. We give you a guide price and introduce you to one local builder we've checked for reviews, company records and insurance. It's free for you; builders pay us for introductions.
Will lots of companies call me?
No. We share your details with one builder only, and only because you asked us to. You can ask us to delete your details at any time.
Do you cover loft conversions?
Yes. See our loft conversion estimate.
Find out what yours will cost
Six questions, a guide price, and one quote from a local builder.
Get my estimate