The 254 x 146 UB37 steel beam is the workhorse of the 254 x 146 range — 256mm deep, 146.4mm wide, with a substantial 10.9mm flange that lifts it well clear of the UB31 below it. It is the section most commonly specified for wide domestic openings where a single beam has to carry a floor and a wall above without intermediate support. Rolled to S355J0 and supplied cut free to any length from 1m to 12m, in mill finish or red oxide primer at no extra cost, with free UK mainland delivery included in the price.
Steel grade — S355J0 to BS EN 10025-2
This beam is rolled in S355J0: a 355 N/mm² minimum yield structural steel with impact toughness certified at 0°C. S355 is the grade UK structural engineers design to by default, carrying roughly 29% more yield strength than the older S275 material some merchants still stock. If your engineer has calculated to S275, an S355 section of the same size will always satisfy that design — but never substitute in the opposite direction without going back to them first.
For a fuller comparison see our guide to S275 vs S355 steel, or the steel grades & standards reference for the full specification we supply against.
Stepping up from the UB31
The 254 x 146 UB31 and UB37 share almost the same footprint — 146mm wide, around 250mm deep — so they detail and bear identically. The difference is in the metal: a 10.9mm flange against 8.6mm, and 37.0 kg/m against 31.1 kg/m.
That buys a major-axis second moment of area of 5,543 cm⁴ against 4,420 cm⁴, a 25% increase, and lifts the plastic modulus from 393.6 cm³ to 483.8 cm³. Where an engineer has run a UB31 and found it marginal on deflection over a 4–5m opening, the UB37 is almost always the next call rather than moving to a 305mm section — it keeps the same structural opening height, which matters when headroom is tight.
This size is common on larger load-bearing wall removals and full-width rear extensions. The UK steel beam size chart lists every UB, UC and PFC size with weights if you are still comparing.
Available finishes — both at the same price
Mill finish is the beam exactly as it leaves the rolling mill: bare structural steel carrying the usual blue-grey mill scale. It suits any job where the RSJ will be encased in plasterboard, boxed in, fire-protected or painted on site — see our guide to boxing in a steel beam.
Red oxide primer is a factory-applied anti-corrosive coating, shot blasted and painted, that protects the beam while it sits on site, in transit, or in an unheated shell before the roof and windows go in. On this section we supply it at no additional cost over mill finish. It is a primer rather than a topcoat — designed to be overpainted, and not a substitute for intumescent fire protection or galvanising in an exposed external location. More in what red oxide primer actually means and whether RSJs need painting at all.
Cut to size — free, to the millimetre
Tell us the length you need and we cut it. There is no charge for cutting and no minimum order beyond a single metre. Enter your dimensions in the calculator above — you can specify several cut lengths on one order and the tool works out what you need. Steel is supplied and billed in whole metres, so a 4.2m requirement is charged as 5m; where you order more than one cut in the same finish, the total is rounded once rather than cut by cut, which keeps the cost down on multi-beam jobs.
Cut tolerance is ±3mm on length. If your opening is tight, allow the usual bearing at each end and confirm the padstone detail with your engineer before ordering. More on what lengths RSJ beams come in.
Section dimensions
| Depth of section (h) | 256.0 mm |
| Width of section (b) | 146.4 mm |
| Web thickness (s) | 6.3 mm |
| Flange thickness (t) | 10.9 mm |
| Root radius (r) | 8.0 mm |
| Depth between fillets (d) | 218.2 mm |
| Mass per metre | 37.0 kg/m |
| Cross-sectional area | 47.2 cm² |
| Surface area per metre | 1.071 m²/m |
Section properties
| Second moment of area, y-y (Iy) | 5,543 cm⁴ |
| Second moment of area, z-z (Iz) | 570.6 cm⁴ |
| Elastic modulus, y-y (Wel,y) | 433.1 cm³ |
| Elastic modulus, z-z (Wel,z) | 77.95 cm³ |
| Plastic modulus, y-y (Wpl,y) | 483.8 cm³ |
| Plastic modulus, z-z (Wpl,z) | 119.4 cm³ |
| Radius of gyration, y-y (iy) | 10.8 cm |
| Radius of gyration, z-z (iz) | 3.4 cm |
Nominal dimensions and properties to BS EN 10365. Figures are published for reference only.
Structural engineer notice
Beam sizing is not something to work out from a table. The correct section for your opening depends on span, the loads carried above, bearing conditions, lateral restraint and the padstone detail — all of which must be calculated by a qualified structural engineer, and in most cases will form part of your building control submission. We supply steel to the specification you give us; we do not provide structural design.
Delivery
Cut-to-size beams are dispatched on a 5–10 working day lead time, with free delivery to UK mainland addresses included in the price — no carriage is added at checkout. A 254 x 146 UB37 weighs 37kg per metre, so a 5m beam is 185kg. Deliveries are kerbside and offloading assistance is required — our vehicles do not carry lifting equipment, so please have suitable labour or plant available. At this weight most customers arrange a telehandler or a team of three.
See how RSJ steel beams are delivered for what to expect on the day, or our delivery & lead times page. Ordering several beams for one project? Trade discounts are available.
Related sections
- 254 x 146 UB31 steel beam — lighter section in the same serial size
- 254 x 146 UB43 steel beam — heaviest section in the same serial size
- 254 x 102 UB28 steel beam — narrower alternative at similar depth
- All RSJ steel beams & columns
- Universal beams (UB)