AG-Renovation Ltd is a trusted extension builder serving customers in Brentford and the surrounding area. Contact us to today to get a competitive ...
At Ferdas Design & Build Ltd we have been fitting bespoke bathrooms since 2013. We pride ourselves on being the go-to bathroom fitters for discerni...
Tomasz Pedowicz
Hi we have 15 years of experience in building and construction industry our specialization is bathrooms and renovations please have a look at the w...
Elite Construction London Ltd
Brentford, TW8
Elite Construction London Ltd has been one of the top providers of building and remodeling services in London for more than ten years.Our goal is ...
Global Building & Designs Ltd is an established and experienced local extension builder in Brentford. Please contact us for a free, no obligation q...
Image Design & Consultants is a trusted extension builder serving customers in Brentford and the surrounding area. Contact us to today to get a com...
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
Andy Harris
Andy Harris Construction is an established and experienced local extension builder in Brentford. Please contact us for a free, no obligation quote ...
JP CONSTRUCTION is an established extension buildering business in Brentford. We come highly recommended and provide competitive quotes for your wo...
Mick Shehabi
Vision Refurbishments Ltd. brings over 10 years of experience in building and construction, including interior and exterior renovations, painting, ...

How much RSJs cost for supply and installation varies depending on the size, type and load-bearing properties, but in Brentford it ranges from £2,104 (Elite Construction London Ltd based in TW8) to £2,704 (Ferdas Design & Build Ltd based in W3).
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 Brentford by posting a job with HaMuch and we will send it to extension builders in Brentford.
"UC beam install 2.5m only (calculations done, building control notification done, no pretty boxing etc.)" - TW8, job posted 03/09/26
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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 - £17,719

Two storey extension - £88,329

Build a timber frame extension - £26,219

Build a swimming pool - £81,219

Single storey extension - £59,384

Side return extension - £43,966

Install an RSJ - £2,419

Outbuilding - £10,219

Build a Mansard loft conversion - £52,219

Loft conversion - £35,805

Build a kitchen extension - £42,219

Hip to gable loft conversion - £42,219

Granny annexe - £87,219

Garden office - £10,219

Convert a Garage - £16,219

Garage - £18,719

Build a flat roof extension - £22,219

Build a dormer loft conversion - £42,219

Concrete foundations - £6,469

Convert a bungalow loft - £29,219

Convert a basement - £39,966