Have worked in building industry for over 30 years contracts from government to private sector.
T.I Building is a trusted extension builder serving customers in Belfast and the surrounding area. Contact us to today to get a competitive quote f...
N W Doyle & Son is a trusted extension builder serving customers in Belfast and the surrounding area. Contact us to today to get a competitive quot...
Belfast, BT8
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 Belfast. SM Plumbing & Heating is a friendly and reliable company based in Belfast who cons...
Belfast, BT17
Trusted and professional extension builder in Belfast. Experienced in all extension buildering work and keeping within budget and on quote. Belfast...
Ballantine building solutions is an established extension buildering business in Belfast. We come highly recommended and provide competitive quotes...
Belfast, BT12
Trusted and professional extension builder in Belfast. Experienced in all extension buildering work and keeping within budget and on quote. Extende...

How much RSJs cost for supply and installation varies depending on the size, type and load-bearing properties, but in Belfast it ranges from £1,176 (Anak based in BT40) to £2,760 (Build a Boiler based in BT67).
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 Belfast by posting a job with HaMuch and we will send it to extension builders in Belfast.
"RSJ installation" - BELFAST, job posted 09/08/25
| Location in UK | Hourly Rate | Daily Rate |
|---|---|---|
| Install An RSJ near Belfast | £23 | £161 |
| Install An RSJ near Carryduff | £23 | £158 |
| Install An RSJ near Holywood | £23 | £159 |
| Install An RSJ near Greenisland | £23 | £153 |
| 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 Saintfield | £23 | £162 |
| Install An RSJ near Hillsborough and Culcavy | £25 | £170 |
| Install An RSJ near Carrickfergus | £23 | £158 |
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 - £16,925

Two storey extension - £87,137

Build a timber frame extension - £25,425

Build a swimming pool - £80,425

Single storey extension - £43,496

Side return extension - £35,029

Install an RSJ - £1,625

Outbuilding - £9,425

Build a Mansard loft conversion - £51,425

Loft conversion - £28,358

Build a kitchen extension - £41,425

Hip to gable loft conversion - £41,425

Granny annexe - £86,425

Garden office - £9,425

Convert a Garage - £15,425

Garage - £17,925

Build a flat roof extension - £21,425

Build a dormer loft conversion - £41,425

Concrete foundations - £5,675

Convert a bungalow loft - £28,425

Convert a basement - £31,029