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Need to find an Extension Builder near you for all your extension buildering work?
Mount Oriel Conversions & Extensions provides a local, t...
Relax... you have found a reliable extension builder in BT8. SM Plumbing & Heating is a friendly and reliable company based in BT8 who consider no ...
From £1,376
Trusted and professional extension builder in BT8. Experienced in all extension buildering work and keeping within budget and on quote. Extended li...

How much RSJs cost for supply and installation varies depending on the size, type and load-bearing properties, but in BT8 it ranges from £1,336 (Mount Oriel Conversions & Extensions based in BT8) to £1,688 (AK Building Services based in BT8).
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 BT8 by posting a job with HaMuch and we will send it to extension builders in BT8.
"RSJ installation" - BELFAST, job posted 09/08/25
| Location in UK | Hourly Rate | Daily Rate |
|---|---|---|
| Install An RSJ near Carryduff | £23 | £158 |
| Install An RSJ near Belfast | £23 | £161 |
| Install An RSJ near Saintfield | £23 | £162 |
| Install An RSJ near Lisburn | £24 | £164 |
| Install An RSJ near Comber | £22 | £160 |
| Install An RSJ near Ballygowan | £24 | £183 |
| Install An RSJ near Holywood | £23 | £159 |
| Install An RSJ near Ballynahinch | £19 | £189 |
| Install An RSJ near Hillsborough and Culcavy | £25 | £170 |
| Install An RSJ near Greenisland | £23 | £153 |
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 - £16,792

Two storey extension - £86,938

Build a timber frame extension - £25,292

Build a swimming pool - £80,292

Single storey extension - £40,840

Side return extension - £33,535

Install an RSJ - £1,492

Outbuilding - £9,292

Build a Mansard loft conversion - £51,292

Loft conversion - £27,113

Build a kitchen extension - £41,292

Hip to gable loft conversion - £41,292

Granny annexe - £86,292

Garden office - £9,292

Convert a Garage - £15,292

Garage - £17,792

Build a flat roof extension - £21,292

Build a dormer loft conversion - £41,292

Concrete foundations - £5,542

Convert a bungalow loft - £28,292

Convert a basement - £29,535