From £17,548
Experienced extension builder ready to quote for your work. J&J Building Solutions is the best extension builder in SE4. No obligation free quotes ...
From £17,596
Experienced extension builder ready to quote for your work. Mr is the best extension builder in SE4. No obligation free quotes and many happy custo...
From £17,484
JK Doors is a trusted extension builder serving customers in SE4 and the surrounding area. Contact us to today to get a competitive quote for exten...
From £17,692
NIECEIC / NAAPIT GASSAFE WATER REGULATIONS We offer services towards completion of high end construction projects to dis...
From £17,892
Need an Extension Builder in SE4? Samuele Paolini has been helping local clients (5 mile radius) with their extension buildering jobs for many yea...
From £17,812
skilled worker who specializes in completing a wide range of building and renovation projects
From £18,116
HOUSE BUILDING SERVICES LIMITED is a trusted extension builder serving customers in SE4 and the surrounding area. Contact us to today to get a comp...
From £17,388
Member since April 2025
Trusted and professional extension builder in SE4. Experienced in all extension buildering work and keeping within budget and on quote. GR MAINTENA...
From £17,812
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
From £17,700
Relax... you have found a reliable extension builder in SE4. Derryard Construction Ltd is a friendly and reliable company based in SE4 who consider...

Underpinning ranges from £17,388 (GR MAINTENANCE LTD based in IG11) to £18,116 (HOUSE BUILDING SERVICES LIMITED based in DA16), 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 SE4 by posting a job with HaMuch and we will send it to extension builders in SE4.
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