CHS 323.9×12.5 vs CF CHS 323.9×12.5
CHS 323.9×12.5 is an CHS Hot-finished section from the UK Blue Book (SCI P363); CF CHS 323.9×12.5 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 1210 cm³ against 1210 cm³ of plastic modulus, a difference of 0.0%. They weigh essentially the same, 96 kg/m and 96 kg/m. Both are about 324 mm deep, so either fits the same construction zone.
| Property | CHS 323.9×12.5 CHS Hot-finished | CF CHS 323.9×12.5 CHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 96 kg/m | 96 kg/m | same |
| Depth | 323.9 mm | 323.9 mm | same |
| Width | 323.9 mm | 323.9 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 122 cm² | 122 cm² | same |
| Second moment, major (Iy) | 14,800 cm⁴ | 14,800 cm⁴ | same |
| Plastic modulus, major (Wpl,y) | 1,210 cm³ | 1,210 cm³ | same |
| Elastic modulus, major (Wel,y) | 917 cm³ | 917 cm³ | same |
| Second moment, minor (Iz) | 14,800 cm⁴ | 14,800 cm⁴ | same |
| Plastic modulus, minor (Wpl,z) | 1,210 cm³ | 1,210 cm³ | same |
| Radius of gyration, minor (iz) | 11 cm | 11 cm | same |
| Torsion constant (It) | 29,700 cm⁴ | 29,700 cm⁴ | same |
CHS 323.9×12.5 to BS EN 10210-2:2006; CF CHS 323.9×12.5 to BS EN 10219-2:2006. Difference is expressed relative to CF CHS 323.9×12.5.
How to choose between them
On stiffness, CF CHS 323.9×12.5 has the larger second moment of area: 14,800 cm⁴ against 14,800 cm⁴, a difference of 0.0%. 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 (12.6 against 12.6 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.