The rolled steel joist itself is usually the smallest line in the bill. What you are buying when a wall comes out is a design, temporary support while the wall above is held up, bearings that can carry the load down to the ground, fire protection for the steel and the making good afterwards. A price quoted for the beam alone is not a price for the job.
The engineer comes before the steel
A structural engineer establishes what the wall is carrying, sizes the beam for that load and span, and specifies the bearing length and the padstones underneath it. Building control will ask for those calculations rather than accept a beam size on trust, and the calculation also decides whether the existing foundation under the bearing is adequate, which is the question that occasionally turns a simple job into a larger one.
Knocking down a wall: temporary works are where the risk sits
Before the wall comes out, everything above it has to be supported. Needles through the wall onto acrow props, sometimes strongboys, sometimes a proper propping design where the load is significant or a floor above is involved. This is skilled work and it is the part of the job where things go badly wrong. It also explains why a single opening in a load bearing wall costs so much more than the same opening in a stud partition.
Cost of RSJ installation: padstones, fire protection and making good
Each end of the beam sits on a padstone sized to spread the load into the masonry. The steel then normally needs fire protection, usually boarding, because unprotected steel loses strength quickly in a fire and the approved document treats the structure of the floor above as something that has to survive long enough to escape. After that comes closing up, plastering, and making good the ceiling and floor at the junction, which is more work than people expect.
Why an RSJ cost calculator can only give a range
The variables are the span, the load above, whether the wall is internal or external, how the bearings are formed, whether a foundation needs underpinning at the ends, access for getting a heavy beam into the middle of a house, and how much making good follows. Those swing the total far more than the steel does, so treat any online figure as a starting range and price the job from the engineer's drawing.
Questions people ask about rsj cost
How much does a steel beam cost against the whole job?
Usually the smallest part. The engineer, the temporary support, the padstones, the fire protection and the making good are where the money goes.
Do I need building regulations approval to remove a wall?
Yes, where the wall is load bearing. The calculations and the beam are inspected, and removing a load bearing wall without approval is a problem on sale.
How do I know if a wall is load bearing?
Do not guess from tapping it. Position relative to the joists above, thickness and what is directly over it all matter, and the answer needs someone competent to look.
Can a beam be installed in a day?
The steel can go in quickly once the propping and bearings are prepared. The preparation, the drying of the padstone bedding and the making good take considerably longer.