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 £2,600
Experienced extension builder ready to quote for your work. RICHARD MORRIS (CONSTRUCTION) is the best extension builder in CM21. No obligation free...
From £2,224
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 £2,368
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
From £2,256
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...
From £2,040
Urban lofts and extensions ltd is an established extension buildering business in CM21. We come highly recommended and provide competitive quotes f...
From £2,200
Our building services company Added Space Ltd have over fifty years combined experience. We have been helping customers in Harlow and the surroundi...
From £1,064
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
From £2,224
Nevill Design & Build specialises in high-quality house extensions, loft conversions, structural alterations, and full refurbishments. We’ve deli...

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 £2,608 (Prestige Construction & Building Services Limited based in CM21).
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 | £289 |
| Install An RSJ near Cheshunt | £48 | £286 |
| Install An RSJ near Epping Forest | £44 | £273 |
| Install An RSJ near Loughton | £44 | £273 |
| Install An RSJ near Welwyn Garden City | £42 | £268 |
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 - £17,495

Two storey extension - £87,993

Build a timber frame extension - £25,995

Build a swimming pool - £80,995

Single storey extension - £54,904

Side return extension - £41,446

Install an RSJ - £2,195

Outbuilding - £9,995

Build a Mansard loft conversion - £51,995

Loft conversion - £33,705

Build a kitchen extension - £41,995

Hip to gable loft conversion - £41,995

Granny annexe - £86,995

Garden office - £9,995

Convert a Garage - £15,995

Garage - £18,495

Build a flat roof extension - £21,995

Build a dormer loft conversion - £41,995

Concrete foundations - £6,245

Convert a bungalow loft - £28,995

Convert a basement - £37,446