The short answer
To size a single RSJ or steel beam, a UK structural engineer typically charges around £200–£500, because it is a focused calculation rather than a full design package. The fee covers sizing the beam for the load above, designing the padstones or bearings it sits on, and producing a calculation sheet and sketch Building Control accepts under Part A. Where several beams are involved — say removing two walls to open up a kitchen-diner — expect £400–£900+. This is the engineer's design fee only; the steel beam itself, its installation, padstones and making good are separate builder and supplier costs. A site visit to measure spans and check the existing structure may add £150–£300. The honest figure depends on how many beams and how complex the load path is.
An RSJ (rolled steel joist) carries the load above a new opening, so its size has to be calculated for the specific span and weight — never guessed. The figures below separate the engineer's fee from the wider cost of fitting the steel.
Typical UK beam fees
- Single beam calculation£200–£500
- Two or more beams£400–£900+
- Padstone / bearing designincluded in fee
- Site visit (if needed)£150–£300
- Steel + fittingseparate builder cost
What the engineer's fee covers
For a steel beam, the structural engineer's fee buys the design work, not the steel. That means calculating the size and grade of beam needed for the span and the load it carries, designing the padstones (the concrete or steel bearings the beam sits on), checking the walls and foundations below can take the concentrated load, and issuing a calculation and sketch Building Control can sign off. For a load-bearing wall removal, the beam calculation is the core of the job.
- Beam sizing for the span and the load above.
- Padstone / bearing design at each end.
- Load-path check down through the walls and foundations.
- Calculation sheet and sketch for Building Control under Part A.
Engineer's fee versus total cost of the beam
It helps to separate the two numbers people mix up. The engineer charges a few hundred pounds to design the beam; the steel and the installation are a much larger, separate cost handled by the builder and steel supplier. Below is the design side — the part the structural engineer covers.
| Engineer scope | Typical fee | Notes |
|---|---|---|
| Single RSJ calculation | £200–£500 | one opening, one beam |
| Two beams | £400–£700 | e.g. through two walls |
| Multiple beams / frame | £700–£900+ | open-plan layouts |
| Site visit (if needed) | £150–£300 | measures and checks existing |
Indicative UK figures for guidance. Sources: Checkatrade structural engineer cost guide; typical 2025/2026 ranges. Steel supply and fitting are separate.
Why the beam must be calculated
When you remove a load-bearing wall, the beam you put in its place has to carry everything the wall used to — the floors, walls or roof above. Get the size wrong and the beam can deflect (sag), causing cracking in the floors and ceilings above, or in a serious case fail. The engineer calculates the precise size, depth and grade so the beam is strong enough and stiff enough, and designs the bearings so the load is safely transferred into the walls below. This is exactly the kind of work Building Control requires calculations for under Part A, and an inspector will check the steel matches the design.
Where the beam fits the wider job
Removing a wall and inserting an RSJ involves several trades and costs: the engineer's design fee, the steel supply, the builder's labour to prop, cut and fit it, padstones and making good, and the Building Control fee. The engineer's part is usually the smallest line, quoted as a fixed fee. If the wall is on or near a boundary, or the beam bears onto a shared wall, a Party Wall Act 1996 notice may also apply — a separate surveyor matter. Getting the engineer involved before the builder starts means the steel can be ordered to the right specification first time.
Why beam size is not a guess
The temptation to copy a neighbour's beam or rely on a builder's rule of thumb is exactly what the engineer's calculation guards against. Two openings that look identical can need very different steel, because the load above them differs — one wall might carry only the floor above, another might carry a floor, a wall and part of the roof. The engineer works out the total load the beam must support, then sizes it not just for strength (so it does not fail) but for deflection (so it does not visibly sag and crack the finishes above). A beam that is strong enough but too shallow can still cause hairline cracking in the ceiling and floor above as it flexes under load. The calculation also fixes the bearing length and the padstone at each end, so the concentrated load is spread safely into the supporting masonry rather than crushing it. Getting all three right — strength, stiffness and bearing — is why the small fee buys real value.
- Load assessment: works out exactly what the beam must carry.
- Strength check: the beam will not fail under that load.
- Deflection check: the beam will not sag and crack finishes above.
- Bearing design: padstones spread the load into the walls below.
Frequently asked questions
Does the structural engineer supply the steel beam?
No. The engineer designs and specifies the beam — its size, grade and bearings — but the steel itself is bought from a supplier or fabricator and fitted by the builder. The engineer's fee is for the calculations only.
Do I need Building Control for an RSJ?
Yes. Inserting a steel beam to remove a load-bearing wall is notifiable to Building Control, and the engineer's calculations are submitted as part of the Building Regulations application. The inspector checks the installed steel matches the design.
Can a builder size an RSJ without an engineer?
Building Control will want calculations from a competent person for a load-bearing beam. An experienced builder may have a view on size, but the formal sign-off and the liability sit with the structural engineer's calculation.
Sources & further reading
- Checkatrade — structural engineer cost guide
- Planning Portal — removing a load-bearing wall
- IStructE — find a chartered structural engineer
Figures on this page are typical UK ranges drawn from published sources and depend on your specific project. They are guidance, not a quotation.