RHS 250×150×5 vs CF RHS 250×150×5
RHS 250×150×5 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). They are close to interchangeable in bending: 324 cm³ against 320 cm³ of plastic modulus, a difference of 1.3%. They weigh essentially the same, 30.4 kg/m and 30.1 kg/m. Both are about 250 mm deep, so either fits the same construction zone.
| Property | RHS 250×150×5 RHS Hot-finished | CF RHS 250×150×5 RHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 30.4 kg/m | 30.1 kg/m | +1.0% |
| Depth | 250 mm | 250 mm | same |
| Width | 150 mm | 150 mm | same |
| 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) | 3,360 cm⁴ | 3,300 cm⁴ | +1.8% |
| Plastic modulus, major (Wpl,y) | 324 cm³ | 320 cm³ | +1.3% |
| Elastic modulus, major (Wel,y) | 269 cm³ | 264 cm³ | +1.9% |
| Second moment, minor (Iz) | 1,530 cm⁴ | 1,510 cm⁴ | +1.3% |
| Plastic modulus, minor (Wpl,z) | 228 cm³ | 225 cm³ | +1.3% |
| Radius of gyration, minor (iz) | 6.28 cm | 6.27 cm | +0.2% |
| Torsion constant (It) | 3,280 cm⁴ | 3,290 cm⁴ | -0.3% |
RHS 250×150×5 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 250×150×5 has the larger second moment of area: 3,360 cm⁴ against 3,300 cm⁴, a difference of 1.8%. 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, the two are equally efficient (10.7 against 10.6 cm³ per kg/m), so on a pure steel-tonnage basis there is nothing to choose between them. The decision comes down to availability, connection detailing and what the rest of the frame uses.
In short, these two are genuine equivalents. Pick whichever your supplier stocks and the rest of the frame already uses.