RSJ Cost UK 2026: How Much Does a Steel Beam Cost?

A typical RSJ steel beam for a domestic project costs around £150–£800 for the steel itself, depending on size, length and finish — but that's only part of the picture. Once you add the structural engineer's calculation and installation labour, the total cost of putting an RSJ in usually lands between £1,000 and £2,500 for a standard opening, and more for a loft conversion or a wide span. "How much does a steel beam cost?" has no single answer because price scales with the beam's weight, length, finish and how hard it is to lift into place — plus the structural engineer's calculation you'll need before anyone fits it. This guide breaks down every part of the cost, gives current price examples, and includes a cost estimator so you can budget your specific span before you buy.

How Much Does an RSJ Cost in the UK?

There are three separate costs in any RSJ project, and lumping them together is where budgets go wrong. First, the steel beam itself — from around £55 for a short 127×76 UB13 up to several hundred pounds for a heavier section cut to a long span. Second, installation — labour, lifting, padstones, propping and making good — which is usually the largest single cost and varies enormously by access and location. Third, the structural engineer's calculation, typically £300–£500, which Building Control will require before signing off a load-bearing alteration. Budget for all three from the start.

RSJ Cost Estimator

Enter your span, the load above the opening and your preferred finish for an indicative steel-and-installation budget. This is a budgeting tool only — the final beam size must come from a structural engineer.

What Affects the Cost of a Steel Beam?

Four factors set the price of the steel itself:

Size and Weight

Steel beams are priced by weight, so a heavier section costs more. For a Universal Beam, the final number in its designation indicates its approximate weight per metre — a 152×89 UB16 is about 16kg per metre, a 203×133 UB30 about 30kg per metre. A bigger opening or heavier load needs a deeper, heavier beam, and the cost rises accordingly.

Length

Longer beams use more steel and cost proportionally more. Buying cut to size means you pay only for the length you need rather than a full 6m bar, which usually works out cheaper and removes the cost and hassle of cutting on site.

Finish

Mill finish (untreated) is the cheapest. Red oxide primer adds a small premium (around 5%) for a protective base coat ready to paint. Galvanising costs more again — typically 15–20% over mill — but is worth it for damp, exposed or external positions. See our guide on whether RSJ beams need painting for which finish suits your situation.

Grade

Most modern RSJ beams are supplied in S355J0 — a higher-strength structural grade than the older S275. Higher-grade steel can sometimes allow a slightly smaller, lighter section for the same load, which can offset the material cost.

Steel Beam Price by Size

The table below shows indicative cut-to-size prices for common domestic RSJ sizes at Rackerman, in mill finish. Prices rise with both section size and length. Use these as a guide to the steel-only cost — installation is separate.

Beam size	Weight	Indicative cut-to-size price (mill)
127×76 UB13	13 kg/m	from ~£55
152×89 UB16	16 kg/m	from ~£79
178×102 UB19	19 kg/m	from ~£85
203×102 UB23	23 kg/m	from ~£102
203×133 UB30	30 kg/m	from ~£119

These are starting prices for shorter cut lengths, and exclude VAT and delivery. A typical domestic opening needs a 3–5 metre beam, so the final steel cost is usually higher — confirm the exact price for your span on each mill finish RSJ beam or red oxide RSJ beam product page.

What the UK Market Charges for a Steel Beam (2026)

To put the prices above in context, we sampled published cut-to-size prices from several UK steel retailers on 10 July 2026. The figures below are per metre, excluding VAT and delivery, for common Universal Beam sections — cross-reference them against our full steel beam size chart. Steel is a commodity, so these move with the market — treat them as a point-in-time guide, not a fixed quote.

The data makes one thing clear: there are really two price tiers in the UK market. Lean online trade fabricators sit at the low end; retail cut-to-size suppliers — with fast delivery, small-order handling and free cutting built in — sit higher, sometimes close to double on the heavier sections. The range below spans both.

Beam size	Weight	UK market price £/m (ex-VAT)
127×76 UB13	13 kg/m	£26 – £49
152×89 UB16	16 kg/m	£32 – £59
178×102 UB19	19 kg/m	£38 – £68
203×102 UB23	23 kg/m	£46 – £75
203×133 UB25	25 kg/m	£50 – £79
203×133 UB30	30 kg/m	£59 – £60 *
254×102 UB28	28 kg/m	£56 – £113
254×146 UB31	31 kg/m	£62 – £110
254×146 UB37	37 kg/m	£73 – £74 *
254×146 UB43	43 kg/m	£84 – £86 *
305×102 UB28	28 kg/m	£56 – £94
305×165 UB40	40 kg/m	£79 – £80 *
356×171 UB51	51 kg/m	£99 – £102 *

Sampled from metals4u, Southend Steels and Steel Beams Direct on 10 July 2026. Per metre, excluding VAT and delivery. Prices are indicative and move with the steel market. Rows marked * are sections where only trade suppliers published a price, so the range sits at the lower, trade end.

⚠ How to read these: they are per-metre rates for stock or longer lengths. A short cut-to-length piece costs significantly more — a single 1-metre cut can exceed £300 once the fixed cutting and handling charge is added, because that cost is spread over just one metre. Use these figures to compare per-metre value between suppliers, not to price one short cut.

Where Rackerman Sits

Rackerman's cut-to-size prices fall within this range — below high-street retail cut-to-size rates and competitive with the online trade suppliers — and, unlike much of the market, every price is shown in full on the product page with no quote form to fill in. For the heavier sections we don't hold as standard stock (such as 305×165 or 356×171), the market runs roughly £79–£102/m ex-VAT; we can source these to order — just ask for a quote.

RSJ Installation Costs

Installation is usually the biggest line in the budget. It covers temporarily propping the structure above, cutting the pockets, lifting the beam into place, fitting padstones to spread the load at each bearing, building the beam in, and making good the surrounding wall. A simple single-storey opening with good access might be £450–£950 for labour; a wider two-storey opening commonly runs £700–£1,500; and loft-conversion steels — often awkward to lift and position — can reach £2,000 or more. Poor access, the need for heavy lifting equipment, or working in an occupied home all push the figure up. Labour also varies by region — London and the South East typically run higher than the North — and you should budget for the incidentals that come with making good: skip hire, plastering, and re-finishing the floor and walls around the new opening.

Structural Engineer Costs

Before any load-bearing beam is fitted, a structural engineer must calculate the size, grade and bearing details, and produce drawings your building control body will sign off. For a single beam this typically costs £300–£500. It is not an optional extra — for a load-bearing alteration, Building Control will require approved structural calculations, and fitting a beam without them can leave you unable to sign off the work, sell the property, or insure it. The engineer's fee is small relative to the risk of an under-specified beam.

Worked Examples

Single-Storey Knock-Through (3m)

A 3m opening between two reception rooms carrying a single wall above might use a 152×89 UB16. Steel in red oxide is roughly £250–£320 cut to size; installation £450–£950; engineer £300–£500. Total in the region of £1,000–£1,800.

Loft Conversion Steel (4m)

Loft conversions usually need several steels to carry the new floor and roof loads. A single 4m loft beam might be a 178×102 UB19, with steel around £350–£450, but installation is higher because of the lifting and access — often £1,200–£2,000 per beam. Multiple beams multiply the cost, which is why loft steelwork commonly runs into several thousand pounds. See our load-bearing wall removal guide for the wider project picture.

What Homeowners Typically Pay, by Project

Most people pricing an RSJ are really costing a specific job. The table below gives indicative all-in ranges — steel, structural engineer and installation combined — for the most common projects. The actual figure depends on span, access and region.

Project	Typical all-in cost
Removing an internal load-bearing wall	£1,500 – £4,000
Kitchen extension / knock-through opening	£2,000 – £5,000
Bi-fold or patio door steel support	£1,500 – £3,500
Loft conversion steels	£3,000 – £8,000

These are whole-project figures including labour and making good — the steel beam itself is usually the smallest line. Wider spans, difficult access, and work in London and the South East push totals toward the top of each range.

How to Keep RSJ Costs Down

Buy the beam cut to size so you pay only for the steel you use and avoid on-site cutting. Choose the right finish for the location rather than over-specifying — mill finish is fine for dry internal use, so there's no need to pay for galvanising indoors. Get the structural calculations done early so the beam size is confirmed before you order, avoiding a wasted purchase. And order in good time: RSJs typically take 5–10 working days for delivery, and rushing rarely saves money.

Buy RSJ Steel Beams at Rackerman

Rackerman supplies RSJ steel beams cut to your exact length in S355J0 grade, in mill finish or red oxide primer, with UK delivery and offload assistance for heavy sections. Already have your engineer's spec? Send us the section and lengths and we'll supply it cut to size, delivered across mainland UK. Not sure what you need yet? Our RSJ size guide and the what is an RSJ guide explain the basics before you order.

Browse cut-to-size RSJ steel beams at Rackerman → · Get a cut-to-size price →

Frequently Asked Questions

How much does a steel beam cost in the UK?

For a typical domestic project, the steel beam alone costs around £200–£950 depending on size, length and finish. Installation usually adds £450–£2,000, and a structural engineer's calculation a further £300–£500. Total project costs commonly fall between £800 and £2,500 for a standard residential opening.

How much does an RSJ cost on its own?

Cut-to-size RSJ steel starts from around £55 for a short 127×76 UB13 and rises with section size and length. A 152×89 UB16 starts from about £79. Heavier sections cut to longer spans run into several hundred pounds.

How much is a steel beam per metre?

Excluding VAT and delivery, common Universal Beams run from roughly £26–£49 per metre for a light 127×76 UB13 up to around £84–£113 per metre for a heavier 254mm section, based on a July 2026 sample of UK cut-to-size suppliers. Lighter sections sit at the lower end; heavier beams and fast-delivery retail suppliers sit higher. Steel is a commodity, so per-metre prices move with the market. Note these are per-metre rates for stock lengths — a short cut-to-length piece costs more once the fixed cutting charge is included.

How much does a 4 metre RSJ cost?

The steel for a 4 metre RSJ typically costs around £200–£600 depending on the section your engineer specifies. The installed cost is higher once engineering, lifting, labour and making good are included — often £1,500–£3,000 for a standard 4m opening. A 5 metre beam costs a little more again, as the section usually steps up to control deflection.

Can I install an RSJ myself?

Some experienced builders fit their own RSJs, but the beam must be sized by a structural engineer's calculation and Building Control approval is required for load-bearing work. Propping the structure and lifting heavy steel safely is skilled work, so most homeowners use a builder for the installation.

How much does it cost to install an RSJ?

Installation typically costs £450–£950 for a simple single-storey opening, £700–£1,500 for a two-storey opening, and up to £2,000 or more for loft-conversion steels. Access, lifting and location are the biggest variables.

Why are steel beams priced by weight?

Steel is bought and sold by weight, so a beam's price tracks its kilograms of steel. The final number in the designation (the 16 in 152×89 UB16) usually indicates the approximate weight per metre in kilograms.

Is red oxide or galvanised better value for an RSJ?

For dry internal use, red oxide primer is the cost-effective choice. Galvanising costs 15–20% more but is worth it for damp, exposed or external positions. Match the finish to the location.

Do I need a structural engineer to fit an RSJ?

Yes. Under Part A of the Building Regulations, any load-bearing beam must be sized by structural calculation, and building control will require an engineer's drawings before sign-off. Budget £300–£500.

How much does a loft conversion steel cost?

Loft conversions usually need several steel beams. Each beam's steel might be £250–£400, but installation is higher due to access and lifting — often £1,200–£2,000 per beam — so loft steelwork commonly totals several thousand pounds.

How long does it take to get an RSJ delivered?

Cut-to-size RSJ beams typically take 5–10 working days for UK delivery. Heavy sections are delivered with offload assistance.

Can I buy an RSJ cut to size?

Yes. Buying cut to size means the beam arrives at the exact length for your opening, so you pay only for the steel you need and avoid cutting on site.

What size RSJ do I need and how does it affect cost?

Beam size depends on span and load and must be confirmed by a structural engineer. A wider opening or heavier load needs a deeper, heavier section, which costs more to supply and install. Use the cost estimator above for an indicative figure.