From £2,200
We provide ‘end-to-end’ design and build services for Loft conversions, Home extension, Kitchen and Bathroom renovations. Our bespoke Design & ...
From £2,504
London, TW9
11th Hour Construction Group are here to help customers who need an Extension Builder in Kew. We offer a competitive rate to complete all your exte...
From £2,352
Relax... you have found a reliable extension builder in Kew. West 1 Construction is a friendly and reliable company based in Kew who consider no jo...
From £2,360
Kew Surrey, TW9
Experienced extension builder ready to quote for your work. The Bespoke Building Company is the best extension builder in Kew. No obligation free q...
From £2,296
Need an Extension Builder in Kew? Edmond & Tann Builders has been helping local clients (10 mile radius) with their extension buildering jobs for m...
From £2,280
Surrey, TW9
London Urban - Intelligent Construction is a trusted extension builder serving customers in Kew and the surrounding area. Contact us to today to ge...
From £2,336
FL Construction London is an established and experienced local extension builder in Kew. Please contact us for a free, no obligation quote and comp...
From £2,168
Need to find an Extension Builder near you for all your extension buildering work?
Embury Building Services Ltd provides a local, trusted e...
From £2,112
Renovations, Building, Servicing and Maintenance is an established extension buildering business in Kew. We come highly recommended and provide com...
From £2,320
Kew Greater London, TW9
Pro Construction London Ltd is more than an ordinary Refurbishment and Building Contractor. We are a building contractor with long experience and 1...

How much RSJs cost for supply and installation varies depending on the size, type and load-bearing properties, but in Kew it ranges from £2,112 (Renovations, Building, Servicing and Maintenance based in TW9) to £2,504 (11th Hour Construction Group based in TW9).
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 Kew by posting a job with HaMuch and we will send it to extension builders in Kew.
"UC beam install 2.5m only (calculations done, building control notification done, no pretty boxing etc.)" - TW8, job posted 03/09/26
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 - £17,593

Two storey extension - £88,139

Build a timber frame extension - £26,093

Build a swimming pool - £81,093

Single storey extension - £56,856

Side return extension - £42,544

Install an RSJ - £2,293

Outbuilding - £10,093

Build a Mansard loft conversion - £52,093

Loft conversion - £34,620

Build a kitchen extension - £42,093

Hip to gable loft conversion - £42,093

Granny annexe - £87,093

Garden office - £10,093

Convert a Garage - £16,093

Garage - £18,593

Build a flat roof extension - £22,093

Build a dormer loft conversion - £42,093

Concrete foundations - £6,343

Convert a bungalow loft - £29,093

Convert a basement - £38,544