RHS 250×150×8 vs CF RHS 250×150×8
RHS 250×150×8 is an RHS Hot-finished section from the UK Blue Book (SCI P363); CF RHS 250×150×8 is the closest equivalent in the UK Blue Book (SCI P363). RHS 250×150×8 carries more bending: 501 cm³ of plastic modulus against 482 cm³, 3.9% more. CF RHS 250×150×8 is the lighter of the two at 46.5 kg/m against 47.7 kg/m, a saving of 2.6% on steel weight. Both are about 250 mm deep, so either fits the same construction zone.
| Property | RHS 250×150×8 RHS Hot-finished | CF RHS 250×150×8 RHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 47.7 kg/m | 46.5 kg/m | +2.6% |
| 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 | 60.8 cm² | 59.2 cm² | +2.7% |
| Second moment, major (Iy) | 5,110 cm⁴ | 4,890 cm⁴ | +4.5% |
| Plastic modulus, major (Wpl,y) | 501 cm³ | 482 cm³ | +3.9% |
| Elastic modulus, major (Wel,y) | 409 cm³ | 391 cm³ | +4.6% |
| Second moment, minor (Iz) | 2,300 cm⁴ | 2,220 cm⁴ | +3.6% |
| Plastic modulus, minor (Wpl,z) | 350 cm³ | 340 cm³ | +2.9% |
| Radius of gyration, minor (iz) | 6.15 cm | 6.12 cm | +0.5% |
| Torsion constant (It) | 5,020 cm⁴ | 5,050 cm⁴ | -0.6% |
RHS 250×150×8 to BS EN 10210-2:2006; CF RHS 250×150×8 to BS EN 10219-2:2006. Difference is expressed relative to CF RHS 250×150×8.
How to choose between them
On stiffness, RHS 250×150×8 has the larger second moment of area: 5,110 cm⁴ against 4,890 cm⁴, a difference of 4.5%. 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 (10.5 against 10.4 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, RHS 250×150×8 is the stronger section and CF RHS 250×150×8 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.