RHS 260×140×5 vs CF RHS 250×150×5
RHS 260×140×5 is an RHS Hot-finished section from the UK Blue Book (SCI P363); CF RHS 250×150×5 is the closest equivalent in the UK Blue Book (SCI P363). RHS 260×140×5 carries more bending: 331 cm³ of plastic modulus against 320 cm³, 3.4% more. They weigh essentially the same, 30.4 kg/m and 30.1 kg/m. RHS 260×140×5 is deeper, 260 mm against 250 mm, which matters where the floor zone is tight.
| Property | RHS 260×140×5 RHS Hot-finished | CF RHS 250×150×5 RHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 30.4 kg/m | 30.1 kg/m | +1.0% |
| Depth | 260 mm | 250 mm | +4.0% |
| Width | 140 mm | 150 mm | -6.7% |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 38.7 cm² | 38.4 cm² | +0.8% |
| Second moment, major (Iy) | 3,530 cm⁴ | 3,300 cm⁴ | +7.0% |
| Plastic modulus, major (Wpl,y) | 331 cm³ | 320 cm³ | +3.4% |
| Elastic modulus, major (Wel,y) | 272 cm³ | 264 cm³ | +3.0% |
| Second moment, minor (Iz) | 1,350 cm⁴ | 1,510 cm⁴ | -10.6% |
| Plastic modulus, minor (Wpl,z) | 216 cm³ | 225 cm³ | -4.0% |
| Radius of gyration, minor (iz) | 5.91 cm | 6.27 cm | -5.7% |
| Torsion constant (It) | 3,080 cm⁴ | 3,290 cm⁴ | -6.4% |
RHS 260×140×5 to BS EN 10210-2:2006; CF RHS 250×150×5 to BS EN 10219-2:2006. Difference is expressed relative to CF RHS 250×150×5.
How to choose between them
On stiffness, RHS 260×140×5 has the larger second moment of area: 3,530 cm⁴ against 3,300 cm⁴, a difference of 7.0%. This matters more often than the strength comparison, because on normal floor spans deflection rather than bending capacity sets the beam size - so if the two are close on modulus but apart on inertia, the stiffer one is usually the better answer even when it is not the stronger one.
Measured as bending capacity per kilogram of steel, RHS 260×140×5 is the more efficient section: 10.9 against 10.6 cm³ per kg/m, 2.4% better. Over a floor of repeated beams that difference is real tonnage, though it is often outweighed by whichever section the fabricator can actually source.
In short, RHS 260×140×5 is the stronger section and CF RHS 250×150×5 is the lighter one; where those are the same section, it is the clear choice, and where they are not, decide on whether your design is governed by capacity or by tonnage.