Colin
We are small building company working for the residential and domestic properties? We work on all types of buildings creating Loft conversion and H...
Dan Nevill
Nevill Design & Build specialises in high-quality house extensions, loft conversions, structural alterations, and full refurbishments. We’ve deli...
From £2,368
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
From £2,608
Prestige Construction & Building Services Ltd is a family-run business with over 30 years industry experience. We offer a Design and Build service ...
From £2,224
Need an Extension Builder in CM21? Loft in Space London has been helping local clients (20 mile radius) with their extension buildering jobs for ma...
From £1,064
Valy
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
From £2,640
Linear Carpentry and Building has been helping customers in Hertfordshire and the surrounding area by providing professional and trustworthy buildi...
From £2,600
Experienced extension builder ready to quote for your work. RICHARD MORRIS (CONSTRUCTION) is the best extension builder in CM21. No obligation free...
From £2,256
With over 20 years of experience we specialise in fit-outs and maximising your living space. Lofts, extensions, basements, new builds and domestic ...
From £2,368
Welstrong Construction is a team of friends and brothers who enjoy working in the building industry and aim to make sure every customer is fully sa...

How much RSJs cost for supply and installation varies depending on the size, type and load-bearing properties, but in CM21 it ranges from £1,064 (V S M Property Services Ltd based in CM23) to £5,352 (Essex loft extensions Ltd based in CM20).
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 CM21 by posting a job with HaMuch and we will send it to extension builders in CM21.
| Location in UK | Hourly Rate | Daily Rate |
|---|---|---|
| Install An RSJ near Harlow | £43 | £288 |
| Install An RSJ near Bishop's Stortford | £42 | £264 |
| Install An RSJ near Ware | £47 | £296 |
| Install An RSJ near Hoddesdon | £46 | £296 |
| Install An RSJ near East Hertfordshire | £44 | £289 |
| Install An RSJ near Hertford | £46 | £290 |
| Install An RSJ near Cheshunt | £48 | £285 |
| Install An RSJ near Epping Forest | £44 | £274 |
| Install An RSJ near Loughton | £44 | £273 |
| Install An RSJ near Welwyn Garden City | £42 | £269 |
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 - £17,870

Two storey extension - £88,556

Build a timber frame extension - £26,370

Build a swimming pool - £81,370

Single storey extension - £62,408

Side return extension - £45,667

Install an RSJ - £2,570

Outbuilding - £10,370

Build a Mansard loft conversion - £52,370

Loft conversion - £37,223

Build a kitchen extension - £42,370

Hip to gable loft conversion - £42,370

Granny annexe - £87,370

Garden office - £10,370

Convert a Garage - £16,370

Garage - £18,870

Build a flat roof extension - £22,370

Build a dormer loft conversion - £42,370

Concrete foundations - £6,620

Convert a bungalow loft - £29,370

Convert a basement - £41,667