From £2,248
Experienced extension builder ready to quote for your work. J&J Building Solutions is the best extension builder in SM3. No obligation free quotes ...
From £2,512
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
From £2,760
Our homes need to be regularly maintained and from time to time they need to be rejuvenated, modernised and enhanced. When it comes to building wor...
From £2,296
Experienced extension builder ready to quote for your work. Mr is the best extension builder in SM3. No obligation free quotes and many happy custo...
From £2,184
JK Doors is a trusted extension builder serving customers in SM3 and the surrounding area. Contact us to today to get a competitive quote for exten...
From £2,392
NIECEIC / NAAPIT GASSAFE WATER REGULATIONS We offer services towards completion of high end construction projects to dis...
From £2,592
Need an Extension Builder in SM3? Samuele Paolini has been helping local clients (5 mile radius) with their extension buildering jobs for many yea...
From £2,816
HOUSE BUILDING SERVICES LIMITED is a trusted extension builder serving customers in SM3 and the surrounding area. Contact us to today to get a comp...
From £2,088
Member since April 2025
Trusted and professional extension builder in SM3. Experienced in all extension buildering work and keeping within budget and on quote. GR MAINTENA...
From £2,400
Relax... you have found a reliable extension builder in SM3. Derryard Construction Ltd is a friendly and reliable company based in SM3 who consider...

How much RSJs cost for supply and installation varies depending on the size, type and load-bearing properties, but in SM3 it ranges from £2,088 (GR MAINTENANCE LTD based in IG11) to £2,816 (HOUSE BUILDING SERVICES LIMITED based in DA16).
Comparing extension builders estimates for fitting an RSJ gives you an idea of who will be better value but the best way to compare costs is to get actual quotes.
Get rates and quotes to install an RSJ in SM3 by posting a job with HaMuch and we will send it to extension builders in SM3.
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 - £17,729

Two storey extension - £88,343

Build a timber frame extension - £26,229

Build a swimming pool - £81,229

Single storey extension - £59,576

Side return extension - £44,074

Install an RSJ - £2,429

Outbuilding - £10,229

Build a Mansard loft conversion - £52,229

Loft conversion - £35,895

Build a kitchen extension - £42,229

Hip to gable loft conversion - £42,229

Granny annexe - £87,229

Garden office - £10,229

Convert a Garage - £16,229

Garage - £18,729

Build a flat roof extension - £22,229

Build a dormer loft conversion - £42,229

Concrete foundations - £6,479

Convert a bungalow loft - £29,229

Convert a basement - £40,074