From £2,312
Need to find an Extension Builder near you for all your extension buildering work?
J Pearson Building provides a local, trusted extension b...
From £1,952
Fitted Solutions was established in 2006 by founder Sam Fisher; with a promise to deliver exceptional craftmanship combined with first class custom...
From £2,104
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
From £2,064
Nestled in the rolling hillside of the West Midlands, Derby is a city birthed by the Roman Empire, and grown in the industrial revolution. Initiall...
From £1,944
The Blackbrook Group offers a one-stop shop for your construction project. We offer support from concept through to completion. We start with an in...

How much RSJs cost for supply and installation varies depending on the size, type and load-bearing properties, but in DE21 it ranges from £1,944 (The Blackbrook Group based in DE22) to £2,312 (J Pearson Building based in DE24).
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 DE21 by posting a job with HaMuch and we will send it to extension builders in DE21.
"RSJ installation" - DERBY, job posted 07/11/25
"RSJ installation Remove wall between kitchen and utility. Fit 3.4m steel beam Obtain Building Control approval and aign off" - DE3, job posted 01/01/70
| Location in UK | Hourly Rate | Daily Rate |
|---|---|---|
| Install An RSJ near Derby | £29 | £227 |
| Install An RSJ near Erewash | £31 | £234 |
| Install An RSJ near Ilkeston | £31 | £236 |
| Install An RSJ near Amber Valley | £32 | £244 |
| Install An RSJ near Belper | £32 | £244 |
| Install An RSJ near Heanor | £31 | £236 |
| Install An RSJ near Long Eaton | £32 | £249 |
| Install An RSJ near Ripley | £32 | £246 |
| Install An RSJ near Broxtowe | £34 | £240 |
| Install An RSJ near Nottingham | £34 | £241 |
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 - £17,375

Two storey extension - £87,813

Build a timber frame extension - £25,875

Build a swimming pool - £80,875

Single storey extension - £52,504

Side return extension - £40,096

Install an RSJ - £2,075

Outbuilding - £9,875

Build a Mansard loft conversion - £51,875

Loft conversion - £32,580

Build a kitchen extension - £41,875

Hip to gable loft conversion - £41,875

Granny annexe - £86,875

Garden office - £9,875

Convert a Garage - £15,875

Garage - £18,375

Build a flat roof extension - £21,875

Build a dormer loft conversion - £41,875

Concrete foundations - £6,125

Convert a bungalow loft - £28,875

Convert a basement - £36,096