From £2,248
Experienced extension builder ready to quote for your work. J&J Building Solutions is the best extension builder in Blackfriars. No obligation free...
From £2,296
Experienced extension builder ready to quote for your work. Mr is the best extension builder in Blackfriars. No obligation free quotes and many hap...
From £2,184
JK Doors is a trusted extension builder serving customers in Blackfriars and the surrounding area. Contact us to today to get a competitive quote f...
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 Blackfriars? Samuele Paolini has been helping local clients (5 mile radius) with their extension buildering jobs for ...
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 Blackfriars and the surrounding area. Contact us to today to ge...
From £2,088
Member since April 2025
Trusted and professional extension builder in Blackfriars. Experienced in all extension buildering work and keeping within budget and on quote. GR ...
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 £2,400
Relax... you have found a reliable extension builder in Blackfriars. Derryard Construction Ltd is a friendly and reliable company based in Blackfri...

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