RHS 150×100×4 vs CF RHS 150×100×4
RHS 150×100×4 is an RHS Hot-finished section from the UK Blue Book (SCI P363); CF RHS 150×100×4 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 97.4 cm³ against 95.7 cm³ of plastic modulus, a difference of 1.8%. They weigh essentially the same, 15.1 kg/m and 14.9 kg/m. Both are about 150 mm deep, so either fits the same construction zone.
| Property | RHS 150×100×4 RHS Hot-finished | CF RHS 150×100×4 RHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 15.1 kg/m | 14.9 kg/m | +1.3% |
| 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 | 19.2 cm² | 18.9 cm² | +1.6% |
| Second moment, major (Iy) | 607 cm⁴ | 595 cm⁴ | +2.0% |
| Plastic modulus, major (Wpl,y) | 97.4 cm³ | 95.7 cm³ | +1.8% |
| Elastic modulus, major (Wel,y) | 81 cm³ | 79.3 cm³ | +2.1% |
| Second moment, minor (Iz) | 324 cm⁴ | 319 cm⁴ | +1.6% |
| Plastic modulus, minor (Wpl,z) | 73.6 cm³ | 72.5 cm³ | +1.5% |
| Radius of gyration, minor (iz) | 4.11 cm | 4.1 cm | +0.2% |
| Torsion constant (It) | 660 cm⁴ | 662 cm⁴ | -0.3% |
RHS 150×100×4 to BS EN 10210-2:2006; CF RHS 150×100×4 to BS EN 10219-2:2006. Difference is expressed relative to CF RHS 150×100×4.
How to choose between them
On stiffness, RHS 150×100×4 has the larger second moment of area: 607 cm⁴ against 595 cm⁴, a difference of 2.0%. 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, the two are equally efficient (6.5 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.