RHS 150×100×5 vs CF RHS 150×100×5
RHS 150×100×5 is an RHS Hot-finished section from the UK Blue Book (SCI P363); CF RHS 150×100×5 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 119 cm³ against 117 cm³ of plastic modulus, a difference of 1.7%. They weigh essentially the same, 18.6 kg/m and 18.3 kg/m. Both are about 150 mm deep, so either fits the same construction zone.
| Property | RHS 150×100×5 RHS Hot-finished | CF RHS 150×100×5 RHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 18.6 kg/m | 18.3 kg/m | +1.6% |
| Depth | 150 mm | 150 mm | same |
| Width | 100 mm | 100 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 23.7 cm² | 23.4 cm² | +1.3% |
| Second moment, major (Iy) | 739 cm⁴ | 719 cm⁴ | +2.8% |
| Plastic modulus, major (Wpl,y) | 119 cm³ | 117 cm³ | +1.7% |
| Elastic modulus, major (Wel,y) | 98.5 cm³ | 95.9 cm³ | +2.7% |
| Second moment, minor (Iz) | 392 cm⁴ | 384 cm⁴ | +2.1% |
| Plastic modulus, minor (Wpl,z) | 90.1 cm³ | 88.3 cm³ | +2.0% |
| Radius of gyration, minor (iz) | 4.07 cm | 4.05 cm | +0.5% |
| Torsion constant (It) | 807 cm⁴ | 809 cm⁴ | -0.2% |
RHS 150×100×5 to BS EN 10210-2:2006; CF RHS 150×100×5 to BS EN 10219-2:2006. Difference is expressed relative to CF RHS 150×100×5.
How to choose between them
On stiffness, RHS 150×100×5 has the larger second moment of area: 739 cm⁴ against 719 cm⁴, a difference of 2.8%. 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 (6.4 against 6.4 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, these two are genuine equivalents. Pick whichever your supplier stocks and the rest of the frame already uses.