RHS 200×100×4 vs CF RHS 200×100×4
RHS 200×100×4 is an RHS Hot-finished section from the UK Blue Book (SCI P363); CF RHS 200×100×4 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 150 cm³ against 148 cm³ of plastic modulus, a difference of 1.4%. They weigh essentially the same, 18.2 kg/m and 18 kg/m. Both are about 200 mm deep, so either fits the same construction zone.
| Property | RHS 200×100×4 RHS Hot-finished | CF RHS 200×100×4 RHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 18.2 kg/m | 18 kg/m | +1.1% |
| Depth | 200 mm | 200 mm | same |
| Width | 100 mm | 100 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 23.2 cm² | 22.9 cm² | +1.3% |
| Second moment, major (Iy) | 1,220 cm⁴ | 1,200 cm⁴ | +1.7% |
| Plastic modulus, major (Wpl,y) | 150 cm³ | 148 cm³ | +1.4% |
| Elastic modulus, major (Wel,y) | 122 cm³ | 120 cm³ | +1.7% |
| Second moment, minor (Iz) | 416 cm⁴ | 411 cm⁴ | +1.2% |
| Plastic modulus, minor (Wpl,z) | 92.8 cm³ | 91.7 cm³ | +1.2% |
| Radius of gyration, minor (iz) | 4.24 cm | 4.23 cm | +0.2% |
| Torsion constant (It) | 983 cm⁴ | 985 cm⁴ | -0.2% |
RHS 200×100×4 to BS EN 10210-2:2006; CF RHS 200×100×4 to BS EN 10219-2:2006. Difference is expressed relative to CF RHS 200×100×4.
How to choose between them
On stiffness, RHS 200×100×4 has the larger second moment of area: 1,220 cm⁴ against 1,200 cm⁴, a difference of 1.7%. 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 (8.2 against 8.2 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.