RSJ and steel beam installation costs in West Wales
If you are removing a load-bearing wall, extending your home or opening up a dark kitchen-diner, you will almost certainly need a structural steel beam. The first question everyone asks is the right one: what will the RSJ installation actually cost?
This guide gives you real published market ranges, explains what moves the number up or down, and sets out the parts people forget to budget for. MGC West Wales designs, fabricates and installs structural steelwork from our base in Aberaeron, working across Ceredigion, Carmarthenshire and Pembrokeshire — and the same rules apply whether the job is a single doorway beam in Lampeter or a run of steels over a new extension in Carmarthen.
Free quotes · No obligation · Based in Aberaeron.
What an RSJ actually is (and why the name is misleading)
RSJ stands for rolled steel joist, but almost no modern beam is a true RSJ. What builders colloquially call an RSJ is usually a universal beam (UB) — an I-section rolled to a standard size and chosen by a structural engineer to carry a specific load over a specific span. You may also hear universal columns (UCs), lintels, and the term "steel" used to mean the whole installation.
None of this matters much to you as the customer. What matters is that the beam is sized by calculation, not guesswork, and that the installation is signed off by building control.
You typically need one when you:
- Remove or open up a load-bearing wall — the classic kitchen-diner knock-through
- Build an extension, where a beam carries the junction between old and new structure
- Form a new opening in an external wall, such as adding bifold doors
- Cut a new stair opening or alter floor joists in a loft conversion
What does an RSJ installation cost?
The honest answer is that the market range is wide, because "an RSJ" can mean a 1-metre lintel over a doorway or a 6-metre beam carrying half a house. Published UK market figures (Checkatrade, updated 2024) give these ballparks, excluding VAT:
| Item | Typical market range |
|---|---|
| Beam supply, 1–5m (up to 46kg/m) | £200 – £950 |
| Installation of the beam alone | £300 – £750 |
| Structural engineer's calculations | from ~£250 |
| Steel priced by weight | £2.50 – £4.50 per kg |
Source: Published UK market figures (Checkatrade, updated 2024), excluding VAT.
Read these as illustrative market context, not a fixed MGC price. In practice, the ranges above cover the beam and its handling only. A realistic installed price for a straightforward single-beam knock-through, including engineer, propping, installation, making good and building control, commonly lands in the low thousands — and a larger or more complex job goes higher. The only reliable figure for your property comes from a site visit, an engineer's calculation and a written, itemised quote.
That is exactly how we price it. No day rates, no allowances, no "we'll see when we open it up" — the number we quote is the number you pay unless you change the scope.
What moves the price
Two beams that look identical from your sofa can be very different jobs. These are the factors that change the cost:
Span and load
Longer spans and heavier loads mean bigger, heavier beams. Steel is priced by weight, so every extra kilogram shows up in the quote.
Access
A ground-floor knock-through with clear access is a different job from a beam that has to be threaded through a terraced house in Aberystwyth, around a staircase, with manual handling instead of machinery.
Temporary support
The wall above has to be held safely while the beam goes in. Propping adds time, materials and labour — and it is never optional.
What the beam sits on
Beams transfer their load to padstones or concrete piers at each end. If the existing wall or foundation cannot take the load, that needs building in — a common surprise in older West Wales cottages.
Utilities in the wall
Electrics, gas, plumbing and heating pipes running through a load-bearing wall have to be moved before it comes down. This is the biggest source of "hidden extra" in this type of job, and a good survey spots it before quoting.
Fire protection
Depending on where the beam sits, building control may require intumescent paint or encasement to give the steel its required fire rating. Your engineer specifies this; it should be in the quote, not discovered later.
Making good
Plastering, flooring and decoration after the structural work are separate from the steelwork itself. Decide early whether you want one team to finish the job or you are doing the finish yourself.
What a proper installed price includes
When you compare quotes, make sure each one covers the same list. A complete beam installation price should include:
The structural engineer's calculations and drawings
Beam fabrication to those calculations, including end plates and connections
Delivery and getting the beam into the building (this is where heavy beams get expensive)
Temporary propping of the structure above
Padstones or bearing details at each end, as specified by the engineer
Installation, levelling and grouting
Fire protection where specified
Building control inspection and sign-off
If a quote is dramatically cheaper than the others, it usually means some of these lines are missing. How to choose a builder in West Wales covers how to compare like for like.
Planning permission and building control
You will almost never need planning permission just to install a beam — but you do need building regulations approval, because you are altering the structure of the building. This is a legal requirement, not a formality: the work falls under Part A (structure) of the Building Regulations (GOV.UK Approved Document A), and your local authority building control (or an approved inspector) must sign it off. Your structural engineer's calculations are the basis of that approval, so this paperwork trail is one of the reasons the engineer is not optional.
Two extra checks worth doing early:
- Listed buildings and conservation areas: if your home is listed or in a conservation area, consent can be needed even for internal structural work. Check with the local planning authority before committing.
- Party walls: if the beam will bear into a wall shared with a neighbour, the Party Wall Act applies and notice is required. Your surveyor or engineer can advise.
How long does it take?
A straightforward single-beam installation on site is often a day or two of disruptive work — but that is the smallest part of the programme. Allow realistic time for the engineer's calculations (often one to two weeks), beam fabrication and delivery (typically two to four weeks depending on the fabricator's schedule), and building control inspection at the right points. From first survey to signed-off steel, a simple job is usually measured in weeks, not days. Welsh weather matters less here than on roofing, but winter ground conditions and access can still slow the making-good afterwards.
The payoff for the wait: done properly, the beam disappears into your home and is never thought about again. Done cheaply, it cracks plaster, sags floors and resurfaces at survey when you come to sell.
Why one team from engineer to installation
Most beam jobs involve four parties: engineer, fabricator, builder and building control. Co-ordinating them yourself means four phone calls every time something changes, and every gap between trades is where delays and extra costs live. MGC handles design-and-build under one contract — engineer's calcs, fabrication in our own yard, installation and sign-off, with one point of contact from first survey to final inspection. You can read more about how we work on our steel structures service page and in our structural steelwork FAQ.
Engineer, fabrication, installation and sign-off under one contract.
Frequently asked questions
Straight answers on cost, planning permission, timelines and what a proper beam installation involves.
Published UK market ranges put the beam itself at £200–£950 and installation at £300–£750 for a typical 1–5m beam, plus around £250 for structural engineer's calculations — all excluding VAT, propping, utilities and making good. A complete single-beam job commonly lands in the low thousands. Treat any figure without a site visit as a guess.
No. The beam is sized by calculation, the structure above has to be temporarily supported, and the work must pass building control inspection. The weight of the steel alone makes it dangerous without the right equipment and experience.
Usually no, unless the building is listed or in a conservation area. You do need building regulations approval under Part A (structure) — this is a legal requirement for removing or altering load-bearing walls.
On site, often one to two days for a straightforward beam. The full programme — engineer's calcs, fabrication, delivery, installation and building control sign-off — usually runs several weeks.
RSJ (rolled steel joist) is the colloquial term; most modern "RSJs" are universal beams rolled to standard sizes. Your structural engineer specifies the exact section and grade for the load and span — the name on the quote matters less than the calculation behind it.
A padstone is a reinforced concrete block that spreads the beam's load into the wall or pier beneath it. Where the existing masonry or foundation is not strong enough to take the concentrated load, padstones (or new piers) must be built — a common and legitimate extra on older properties.
Get a fixed price for your beam.
Tell us the wall you want to open up, the extension you are planning or the beam you have been quoted for elsewhere — we will survey, calculate and quote it properly.
No day rates, no allowances, no "we'll see when we open it up" — the number we quote is the number you pay unless you change the scope.
We aim to reply within one working day. No spam, no hard sell.
Serving Ceredigion, Carmarthenshire and Pembrokeshire — from our base in Aberaeron.
Let’s talk about your steel beam.
Free, no-obligation quotes on structural steelwork anywhere in West Wales.