Jay Reid
CK Constructions & Development Ltd is a trusted extension builder serving customers in W1K and the surrounding area. Contact us to today to get a c...
A to Z Builders Ltd are here to help customers who need an Extension Builder in W1K. We offer a competitive rate to complete all your extension bui...
JK Doors is a trusted extension builder serving customers in W1K and the surrounding area. Contact us to today to get a competitive quote for exten...
JM Building Services is a trusted extension builder serving customers in W1K and the surrounding area. Contact us to today to get a competitive quo...
Buildwiser is a trusted extension builder serving customers in W1K and the surrounding area. Contact us to today to get a competitive quote for ext...
F & F Building Services is an established extension buildering business in W1K. We come highly recommended and provide competitive quotes for your ...
Anthony Sullivan
We build Lofts. We build Extensions. We undertake conversions. Our Terms and conditions apply as shown in our starter packs.
From £17,652
Plansing Ltd
Experience the best architectural design services with PLANSING, where we flawlessly integrate innovative architectural designer products to bring ...
From £15,708
London Design And Build
Here at London Design and Build, our team of architects, interior designers, structural engineers and contractors, offer a bespoke, turn-key servic...

Underpinning ranges from £15,708 (London Design And Build based in SW1A) to £19,820 (Reid and Co Developments Ltd based in NW8), 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 - £17,859

Two storey extension - £88,539

Build a timber frame extension - £26,359

Build a swimming pool - £81,359

Single storey extension - £62,184

Side return extension - £45,541

Install an RSJ - £2,559

Outbuilding - £10,359

Build a Mansard loft conversion - £52,359

Loft conversion - £37,118

Build a kitchen extension - £42,359

Hip to gable loft conversion - £42,359

Granny annexe - £87,359

Garden office - £10,359

Convert a Garage - £16,359

Garage - £18,859

Build a flat roof extension - £22,359

Build a dormer loft conversion - £42,359

Concrete foundations - £6,609

Convert a bungalow loft - £29,359

Convert a basement - £41,541