From £2,600
Buckinghamshire, W3
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
From £2,504
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...
From £2,704
London, W3
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...
From £2,224
Need to find an Extension Builder near you for all your extension buildering work?
Nomex Design provides a local, trusted extension builder...
From £2,432
London, W3
Our building services company Fox Construct Ltd is a family-run business based in West London with a solid team of professionals dedicated to compl...
From £2,200
Relax... you have found a reliable extension builder in W3. Raremade is a friendly and reliable company based in W3 who consider no job as too big ...
From £2,408
Greater London, W3
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
From £2,392
PJS Building & Maintenance Ltd is a trusted extension builder serving customers in W3 and the surrounding area. Contact us to today to get a compet...
From £2,232
Acton, W3
LINE BUILDERS LTD is an established extension buildering business in W3. We come highly recommended and provide competitive quotes for your work.
From £2,416
R Burton & Sons Builders are here to help customers who need an Extension Builder in W3. We offer a competitive rate to complete all your extension...

How much RSJs cost for supply and installation varies depending on the size, type and load-bearing properties, but in W3 it ranges from £2,200 (Raremade based in W3) 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 W3 by posting a job with HaMuch and we will send it to extension builders in W3.
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 - £17,711

Two storey extension - £88,317

Build a timber frame extension - £26,211

Build a swimming pool - £81,211

Single storey extension - £59,224

Side return extension - £43,876

Install an RSJ - £2,411

Outbuilding - £10,211

Build a Mansard loft conversion - £52,211

Loft conversion - £35,730

Build a kitchen extension - £42,211

Hip to gable loft conversion - £42,211

Granny annexe - £87,211

Garden office - £10,211

Convert a Garage - £16,211

Garage - £18,711

Build a flat roof extension - £22,211

Build a dormer loft conversion - £42,211

Concrete foundations - £6,461

Convert a bungalow loft - £29,211

Convert a basement - £39,876