Cost calculator
RSJ installation cost calculator
The steel is rarely the expensive part. Design, temporary propping, getting a heavy beam into position and protecting it afterwards is where the money goes — and where quotes diverge.
Clear span the beam must cross.
Broad trade availability keeps day rates near the national average.
Estimated range, ex VAT
£4,300 – £8,800
- Labour (typical)
- £3,250
- Materials (typical)
- £3,250
Guidance only. A real quotation depends on site conditions, specification and access — which is exactly what an independent review of your own quote will tell you.
What affects the cost
Span and load
A longer span or heavier load means a deeper section — steel weight rises quickly and so does the handling requirement.
Access
Getting a 200kg beam into a terraced house through a hallway is very different from a rear opening with garden access.
Padstones and bearings
Concrete padstones or spreader plates must be designed and cast at each end.
Fire protection
Boarding or intumescent coating to achieve the required fire rating.
Temporary propping
Acrow props, strongboys and needling, particularly on external walls.
Regional pricing differences
Materials cost roughly the same everywhere in the UK; labour does not. Use the region selector above to apply a local index — London and the South East typically run 15–30% above the national average, while the North East, Northern Ireland and Yorkshire sit below it.
Labour vs materials
Roughly 50% of this type of work is labour and 50% materials. Steel is priced per tonne; installation labour, propping and access often exceed the steel cost on domestic jobs.
Common hidden costs
- Structural engineer's fee and building control application.
- Craneage or specialist lifting where access is tight.
- Corrosion protection where a beam is exposed to weather.
- Making good and boxing in, which is a separate trade.
How to save money
- Reduce the span, even by 300mm, to bring the beam into a lighter section.
- Use two smaller beams with a central pier if the layout allows.
- Have the engineer specify the beam before requesting quotes so every builder prices the same steel.
- Bundle the steel work with the rest of the project rather than as a standalone visit.
Frequently asked questions
How much does an RSJ cost to install?
£1,800–£4,500 for a typical domestic 3–4m beam including design, installation and making good in 2026.
How much is the steel itself?
Often only £300–£900 for a domestic beam. The rest is design, labour, propping and finishing.
Do I need an engineer?
Yes. Building control will require calculations before signing off any structural opening.
Does the beam need fire protection?
Yes, in habitable areas the steel must be protected to the required fire resistance period, usually with plasterboard encasement.
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