From £17,900
Starfish Properties is a trusted extension builder serving customers in W1 and the surrounding area. Contact us to today to get a competitive quote...
From £17,588
Dominic Payte - Design & Build is an established extension buildering business in W1. We come highly recommended and provide competitive quotes for...
From £17,444
Hestia Contractors Ltd are here to help customers who need an Extension Builder in W1. We offer a competitive rate to complete all your extension b...
From £17,540
Independent construction company we have wide range of experience, including newconstruction, renovation, design build and retail stores. We provid...
From £17,732
We are specialised in: demolition services, foundation services, property extension, general bricklaying, internal renovation and configuration, ca...
From £17,932
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
From £17,564
Experienced extension builder ready to quote for your work. Cornerstone is the best extension builder in W1. No obligation free quotes and many hap...
From £17,484
JK Doors is a trusted extension builder serving customers in W1 and the surrounding area. Contact us to today to get a competitive quote for extens...
From £17,788
Grand Phase Ltd is a trusted extension builder serving customers in W1 and the surrounding area. Contact us to today to get a competitive quote for...
From £17,812
Teammax LTD are here to help customers who need an Extension Builder in W1. We offer a competitive rate to complete all your extension buildering j...

Underpinning ranges from £17,444 (Hestia Contractors Ltd based in W1B) to £17,932 (Sehem Design based in W1F), 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 W1 by posting a job with HaMuch and we will send it to extension builders in W1.
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 - £17,678

Two storey extension - £88,268

Build a timber frame extension - £26,178

Build a swimming pool - £81,178

Single storey extension - £58,568

Side return extension - £43,507

Install an RSJ - £2,378

Outbuilding - £10,178

Build a Mansard loft conversion - £52,178

Loft conversion - £35,423

Build a kitchen extension - £42,178

Hip to gable loft conversion - £42,178

Granny annexe - £87,178

Garden office - £10,178

Convert a Garage - £16,178

Garage - £18,678

Build a flat roof extension - £22,178

Build a dormer loft conversion - £42,178

Concrete foundations - £6,428

Convert a bungalow loft - £29,178

Convert a basement - £39,507