1 review
From £2,392
NIECEIC / NAAPIT GASSAFE WATER REGULATIONS We offer services towards completion of high end construction projects to dis...
"Did callout made safe my elctrical work thanks" - reviewed 16/05/23, REECYRUSSO
From £2,592
Need an Extension Builder in WD3? Samuele Paolini has been helping local clients (5 mile radius) with their extension buildering jobs for many yea...
From £2,480
Member since August 2026
Relax... you have found a reliable extension builder in WD3. ABC Associates STRUCTURES 4 U is a friendly and reliable company based in WD3 who cons...
From £2,392
Need an Extension Builder in WD3? VA Structures has been helping local clients (10 mile radius) with their extension buildering jobs for many years...
From £2,480
Trusted and professional extension builder in WD3. Experienced in all extension buildering work and keeping within budget and on quote. DC Build & ...
From £2,512
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
From £2,352
I am a qualified, builder, electrician and plumber. I have been working in the construction industry for over 23 years and have built everything fr...
From £2,504
Hi we have 15 years of experience in building and construction industry our specialization is bathrooms and renovations please have a look at the w...
From £2,624
Reliable and experienced extension builders with competitive rates and good at keeping within budget. Happy to provide examples of extension builde...
From £2,120
NISUP BUILDING SERVICES Company specializes in the domestic and commercial building industry :1. Refurbishm...

How much RSJs cost for supply and installation varies depending on the size, type and load-bearing properties, but in WD3 it ranges from £2,120 (Nisup Building Services based in HA8) to £2,624 (LALI BUILDERS based in NW10).
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 WD3 by posting a job with HaMuch and we will send it to extension builders in WD3.
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 - £17,745

Two storey extension - £88,367

Build a timber frame extension - £26,245

Build a swimming pool - £81,245

Single storey extension - £59,896

Side return extension - £44,254

Install an RSJ - £2,445

Outbuilding - £10,245

Build a Mansard loft conversion - £52,245

Loft conversion - £36,045

Build a kitchen extension - £42,245

Hip to gable loft conversion - £42,245

Granny annexe - £87,245

Garden office - £10,245

Convert a Garage - £16,245

Garage - £18,745

Build a flat roof extension - £22,245

Build a dormer loft conversion - £42,245

Concrete foundations - £6,495

Convert a bungalow loft - £29,245

Convert a basement - £40,254