From £17,596
Need to find an Extension Builder near you for all your extension buildering work?
Pillar Contractors Ltd provides a local, trusted extensi...
From £17,972
We are a Design and Build Company, based in London.We focus on super prime and luxury residential renovations in and around London and internationa...
From £17,540
We Love Build - Three Arches is an established extension buildering business in W1K. We come highly recommended and provide competitive quotes for ...
From £17,524
Luxe Refurbs is an established extension buildering business in W1K. We come highly recommended and provide competitive quotes for your work.
From £17,588
Dominic Payte - Design & Build is an established extension buildering business in W1K. We come highly recommended and provide competitive quotes fo...
From £17,900
Starfish Properties is a trusted extension builder serving customers in W1K and the surrounding area. Contact us to today to get a competitive quot...
From £17,604
Trusted and professional extension builder in W1K. Experienced in all extension buildering work and keeping within budget and on quote. The Maybria...
From £17,852
Experienced extension builder ready to quote for your work. Mayfair Design is the best extension builder in W1K. No obligation free quotes and many...
From £17,580
Experienced extension builder ready to quote for your work. Azur London is the best extension builder in W1K. No obligation free quotes and many ha...
From £17,884
Experienced extension builder ready to quote for your work. Future Homes Design and Build is the best extension builder in W1K. No obligation free ...

Underpinning ranges from £17,524 (Luxe Refurbs based in W1J) to £17,972 (We Love Build based in W1J), but the final cost will depend on the method of underpinning used, how much of your foundations need underpinning and where you live.
Comparing extension builders estimates for underpinning gives you an idea of who will be better value but the best way to compare costs is to get actual quotes.
Get quotes to underpin your home in W1K by posting a job with HaMuch and we will send it to extension builders in W1K.
Whether you’re looking to extend your kitchen with a side return extension or you want to convert your basement into a liveable space, read our cost guides to get an idea of how much each project costs before getting a more accurate quote from our database of reliable tradespeople.

Underpin a building - £17,704

Two storey extension - £88,306

Build a timber frame extension - £26,204

Build a swimming pool - £81,204

Single storey extension - £59,080

Side return extension - £43,795

Install an RSJ - £2,404

Outbuilding - £10,204

Build a Mansard loft conversion - £52,204

Loft conversion - £35,663

Build a kitchen extension - £42,204

Hip to gable loft conversion - £42,204

Granny annexe - £87,204

Garden office - £10,204

Convert a Garage - £16,204

Garage - £18,704

Build a flat roof extension - £22,204

Build a dormer loft conversion - £42,204

Concrete foundations - £6,454

Convert a bungalow loft - £29,204

Convert a basement - £39,795