“RSJ sizes and prices” is really two questions glued together. First: which section? Second: what does that section cost per metre this year, and what does the whole job cost once you stop pretending steel is the only line item?
Prices move with scrap markets, region and finish (painted, primed, galvanised). Treat the figures below as 2026 planning bands for the UK, not a quote. For a live estimate plug numbers into the cost calculator. For sizing context keep the domestic span table nearby.
Common sizes and indicative £/m (material only)
| Section (UB / RSJ style) | Approx. kg/m | Indicative UK £/m (2026) |
|---|---|---|
| 152×89×16 | 16 | £35–£50 |
| 178×102×19 | 19 | £40–£55 |
| 203×133×25 | 25 | £55–£75 |
| 203×133×30 | 30 | £65–£85 |
| 254×146×31 | 31 | £75–£95 |
| 254×146×37 | 37 | £85–£110 |
| 305×165×40 | 40 | £95–£125 |
| 305×165×46 | 46 | £110–£140 |
| 356×171×45 | 45 | £120–£155 |
| 356×171×51 | 51 | £135–£175 |
Galvanising, drilling, end plates, camber and odd cut lengths push the ticket up. Delivery for a single beam often adds £80–£200+ depending on distance and crane offload. Restricted urban drops cost more.
These £/m bands are for ordinary primed or painted supply conversations. Stainless, weathering steel and complex fabrication are different markets.
Size first, price second
Cheapest £/m is useless if the section fails deflection. Pick a planning size from the span table or size chart, then price it. Tools that help:
A homeowner who shops £/m before span and load width usually buys twice.
Worked example 1: 4.3 m of 203×133×25
Kitchen knock-through planning size, clear span 4.0 m, bearings included in 4.3 m cut.
- Steel: 4.3 × ~£68 ≈ £290 (mid-band)
- Delivery: ~£140
- VAT on supply where applicable
- Still missing: engineer, Building Control, padstones, labour, making-good
That is why a “£300 beam” becomes a multi-thousand-pound project. Full picture: how much to install an RSJ. Narrative version: kitchen knock-through case study.
Worked example 2: 5.3 m of 254×146×37
Open-plan rear opening. Mid-band £/m say £95.
- Steel: 5.3 × £95 ≈ £500
- Delivery / possible crane assist: £200–£600
- Heavier temporary works and making-good than example 1
Steel is still not the dominant cost. Labour, fees and finishes are. See the 5 m span guide.
Worked example 3: 6.3 m of 305×165×46
Long opening. Mid-band £/m say £125.
- Steel: 6.3 × £125 ≈ £790
- Cranage can exceed the steel line on awkward sites
- Installed project often lands in the high thousands before decoration
Details: 6 m span guide.
What changes the steel price besides kg/m
Region. South East pricing often sits above many northern quotes for the same section, though transport quirks can flip that.
Finish. Primer only vs painted vs galvanised. Galvanising helps in damp or external exposure but adds cost and lead time.
Fabrication. End plates, cleats, slotted holes, notches for services, welded stiffeners. A “beam” quote and a “mark as drawing” quote are different animals.
Quantity. One awkward bar costs more per metre than a bundle for a contractor account.
Lead time. Rush cuts and small stockholders’ one-off jobs carry premiums.
Grade. Modern UB supply is often S355. Confirm what you are buying. Older stock conversations sometimes mix grades casually. Do not.
UK vs online stockists
Depot collection can beat delivered web prices if you have suitable transport and can handle the mass safely. Online cut-to-length is convenient for homeowners. Always confirm:
- exact designation and grade
- length tolerance
- camber
- whether end plates are included
- who offloads
Poland / EU readers: relative prices differ. See our UK and Poland price overview.
How steel cost compares to project cost
Rule of thumb for a single domestic knock-through: steel supply is often 10–25% of the structure-focused total once engineer, Building Control, labour, temporary works and basic making-good are included. Decorative kitchens and flooring sit on top of that.
| Project shape | Steel share of structure budget (rough) |
|---|---|
| Short 3 m opening, easy access | Higher steel share, still not majority |
| Standard 4 m kitchen opening | Often teens of percent |
| Long 5–6 m opening with crane | Steel share can fall as lifting rises |
Budget with the install cost article and how much an RSJ costs, not with a stockholder PDF alone.
Rising prices and quotes that go stale
Steel markets move. A quote from January can look optimistic in June. Ask how long a price is held, and whether delivery is included. Background on volatility: rising steel prices and project impact.
Build 10–15% contingency on the whole project for making-good and small drawing changes. Contingency on steel alone is not enough.
Buying checklist
- Engineer’s mark, length and grade on paper
- Padstone schedule (separate purchase often)
- Fire protection method and who supplies it
- Delivery / crane responsibility written down
- Compare at least two stockholders on the same mark
- Check lead times against Building Control programme
- Do not order from a planning table screenshot
Where to start shopping conversations: where to buy RSJ beams online.
FAQ
Why is my quote higher than your £/m table?
Because length premiums, fabrication, delivery, finish and region sit on top. Tables are bands, not invoices.
Is galvanising worth it indoors?
Often primer plus suitable encasement is enough indoors. Damp rooms, external exposure or severe environments change the advice. Ask the engineer and follow the specification.
Can I save money by buying a heavier second-hand beam?
Sometimes scrap yards sell surplus. Matching length, section, straightness and certification is the hard part. For structural work, documentation matters.
Do end plates come as standard?
Not always. Many domestic beams need fabricated ends. Price the drawing, not a bare bar.
How to request a usable quote
Send the stockholder: section mark, cut length, grade, finish, end plates/holes if known, delivery postcode, offload method. Vague �4 m RSJ please� invites the wrong bar.
Cross-check planning size via span table tool and beam size calculator. Then price. Then add labour using install costs.
FAQ � prices
Why is online L/m different from depot? Delivery, cutting, small-order premiums and finish.
Does galvanising double the price? Often a large uplift � ask specifically.
Is the cheapest section always cheapest installed? No. Undersized steel that fails deflection wastes the whole programme.
Bottom line
Memorise ballpark £/m if you like. Budget the installed total. Get the section from an engineer, then ask stockholders for firm quotes on that exact mark.
About Anna Kowalska
Researches steel prices, supplier practices and project costs for UK and Poland readers. Compiles publicly available standards into plain-English explainers.
