From £2,248
Experienced extension builder ready to quote for your work. J&J Building Solutions is the best extension builder in City Of Westminster. No obligat...
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 City Of Westminster. Derryard Construction Ltd is a friendly and reliable company based in ...
From £2,168
B J CULLEN BUILDERS are here to help customers who need an Extension Builder in City Of Westminster. We offer a competitive rate to complete all yo...
From £2,232
Relax... you have found a reliable extension builder in City Of Westminster. Major Building Contractors Ltd is a friendly and reliable company base...
From £2,384
Need to find an Extension Builder near you for all your extension buildering work?
Sz Builders provides a local, trusted extension builderi...
From £2,912
Experienced extension builder ready to quote for your work. Render is the best extension builder in City Of Westminster. No obligation free quotes ...
From £2,096
Experienced extension builder ready to quote for your work. Jhon is the best extension builder in City Of Westminster. No obligation free quotes an...
From £2,080
Member since August 2025
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
From £2,392
NIECEIC / NAAPIT GASSAFE WATER REGULATIONS We offer services towards completion of high end construction projects to dis...

How much RSJs cost for supply and installation varies depending on the size, type and load-bearing properties, but in City Of Westminster it ranges from £2,080 (Can design and Construction based in Ig11) to £2,912 (Render based in IG1).
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 City Of Westminster by posting a job with HaMuch and we will send it to extension builders in City Of Westminster.
"RSJ re-installation" - N16, job posted 04/10/25
| Location in UK | Hourly Rate | Daily Rate |
|---|---|---|
| Install An RSJ near London | £45 | £274 |
| Install An RSJ near Camden Town | £44 | £277 |
| Install An RSJ near Belgravia | £44 | £276 |
| Install An RSJ near Chelsea | £44 | £276 |
| Install An RSJ near Lambeth | £44 | £275 |
| Install An RSJ near Kensington | £44 | £277 |
| Install An RSJ near Islington | £45 | £276 |
| Install An RSJ near Fulham | £44 | £277 |
| Install An RSJ near Camberwell | £44 | £276 |
| Install An RSJ near Bethnal Green | £45 | £276 |
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 - £17,642

Two storey extension - £88,214

Build a timber frame extension - £26,142

Build a swimming pool - £81,142

Single storey extension - £57,848

Side return extension - £43,102

Install an RSJ - £2,342

Outbuilding - £10,142

Build a Mansard loft conversion - £52,142

Loft conversion - £35,085

Build a kitchen extension - £42,142

Hip to gable loft conversion - £42,142

Granny annexe - £87,142

Garden office - £10,142

Convert a Garage - £16,142

Garage - £18,642

Build a flat roof extension - £22,142

Build a dormer loft conversion - £42,142

Concrete foundations - £6,392

Convert a bungalow loft - £29,142

Convert a basement - £39,102