CHS 355.6×12.5 vs CF CHS 355.6×12.5
CHS 355.6×12.5 is an CHS Hot-finished section from the UK Blue Book (SCI P363); CF CHS 355.6×12.5 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 1470 cm³ against 1470 cm³ of plastic modulus, a difference of 0.0%. They weigh essentially the same, 106 kg/m and 106 kg/m. Both are about 356 mm deep, so either fits the same construction zone.
| Property | CHS 355.6×12.5 CHS Hot-finished | CF CHS 355.6×12.5 CHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 106 kg/m | 106 kg/m | same |
| Depth | 355.6 mm | 355.6 mm | same |
| Width | 355.6 mm | 355.6 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 135 cm² | 135 cm² | same |
| Second moment, major (Iy) | 19,900 cm⁴ | 19,900 cm⁴ | same |
| Plastic modulus, major (Wpl,y) | 1,470 cm³ | 1,470 cm³ | same |
| Elastic modulus, major (Wel,y) | 1,120 cm³ | 1,120 cm³ | same |
| Second moment, minor (Iz) | 19,900 cm⁴ | 19,900 cm⁴ | same |
| Plastic modulus, minor (Wpl,z) | 1,470 cm³ | 1,470 cm³ | same |
| Radius of gyration, minor (iz) | 12.1 cm | 12.1 cm | same |
| Torsion constant (It) | 39,700 cm⁴ | 39,700 cm⁴ | same |
CHS 355.6×12.5 to BS EN 10210-2:2006; CF CHS 355.6×12.5 to BS EN 10219-2:2006. Difference is expressed relative to CF CHS 355.6×12.5.
How to choose between them
On stiffness, CF CHS 355.6×12.5 has the larger second moment of area: 19,900 cm⁴ against 19,900 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 (13.9 against 13.9 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.