RHS 200×120×5 vs CF RHS 200×120×5
RHS 200×120×5 is an RHS Hot-finished section from the UK Blue Book (SCI P363); CF RHS 200×120×5 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 205 cm³ against 201 cm³ of plastic modulus, a difference of 2.0%. They weigh essentially the same, 24.1 kg/m and 23.8 kg/m. Both are about 200 mm deep, so either fits the same construction zone.
| Property | RHS 200×120×5 RHS Hot-finished | CF RHS 200×120×5 RHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 24.1 kg/m | 23.8 kg/m | +1.3% |
| Depth | 200 mm | 200 mm | same |
| Width | 120 mm | 120 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 30.7 cm² | 30.4 cm² | +1.0% |
| Second moment, major (Iy) | 1,690 cm⁴ | 1,650 cm⁴ | +2.4% |
| Plastic modulus, major (Wpl,y) | 205 cm³ | 201 cm³ | +2.0% |
| Elastic modulus, major (Wel,y) | 168 cm³ | 165 cm³ | +1.8% |
| Second moment, minor (Iz) | 762 cm⁴ | 750 cm⁴ | +1.6% |
| Plastic modulus, minor (Wpl,z) | 144 cm³ | 141 cm³ | +2.1% |
| Radius of gyration, minor (iz) | 4.98 cm | 4.97 cm | +0.2% |
| Torsion constant (It) | 1,650 cm⁴ | 1,650 cm⁴ | same |
RHS 200×120×5 to BS EN 10210-2:2006; CF RHS 200×120×5 to BS EN 10219-2:2006. Difference is expressed relative to CF RHS 200×120×5.
How to choose between them
On stiffness, RHS 200×120×5 has the larger second moment of area: 1,690 cm⁴ against 1,650 cm⁴, a difference of 2.4%. 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 (8.5 against 8.4 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.