From £2,248
Experienced extension builder ready to quote for your work. J&J Building Solutions is the best extension builder in Orpington. No obligation free q...
From £2,384
Experienced extension builder ready to quote for your work. CC&D BUILDING LTD is the best extension builder in Orpington. No obligation free quotes...
From £2,296
Experienced extension builder ready to quote for your work. Mr is the best extension builder in Orpington. No obligation free quotes and many happy...
From £2,184
JK Doors is a trusted extension builder serving customers in Orpington and the surrounding area. Contact us to today to get a competitive quote for...
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 Orpington? Samuele Paolini has been helping local clients (5 mile radius) with their extension buildering jobs for ma...
From £2,512
skilled worker who specializes in completing a wide range of building and renovation projects
From £2,816
HOUSE BUILDING SERVICES LIMITED is a trusted extension builder serving customers in Orpington and the surrounding area. Contact us to today to get ...
From £2,088
Member since April 2025
Trusted and professional extension builder in Orpington. Experienced in all extension buildering work and keeping within budget and on quote. GR MA...
From £2,400
Relax... you have found a reliable extension builder in Orpington. Derryard Construction Ltd is a friendly and reliable company based in Orpington ...

How much RSJs cost for supply and installation varies depending on the size, type and load-bearing properties, but in Orpington 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 Orpington by posting a job with HaMuch and we will send it to extension builders in Orpington.
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 - £17,691

Two storey extension - £88,287

Build a timber frame extension - £26,191

Build a swimming pool - £81,191

Single storey extension - £58,824

Side return extension - £43,651

Install an RSJ - £2,391

Outbuilding - £10,191

Build a Mansard loft conversion - £52,191

Loft conversion - £35,543

Build a kitchen extension - £42,191

Hip to gable loft conversion - £42,191

Granny annexe - £87,191

Garden office - £10,191

Convert a Garage - £16,191

Garage - £18,691

Build a flat roof extension - £22,191

Build a dormer loft conversion - £42,191

Concrete foundations - £6,441

Convert a bungalow loft - £29,191

Convert a basement - £39,651