CHS 508×12.5 vs CF CHS 508×12.5
CHS 508×12.5 is an CHS Hot-finished section from the UK Blue Book (SCI P363); CF CHS 508×12.5 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 3070 cm³ against 3070 cm³ of plastic modulus, a difference of 0.0%. They weigh essentially the same, 153 kg/m and 153 kg/m. Both are about 508 mm deep, so either fits the same construction zone.
| Property | CHS 508×12.5 CHS Hot-finished | CF CHS 508×12.5 CHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 153 kg/m | 153 kg/m | same |
| Depth | 508 mm | 508 mm | same |
| Width | 508 mm | 508 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 195 cm² | 195 cm² | same |
| Second moment, major (Iy) | 59,800 cm⁴ | 59,800 cm⁴ | same |
| Plastic modulus, major (Wpl,y) | 3,070 cm³ | 3,070 cm³ | same |
| Elastic modulus, major (Wel,y) | 2,350 cm³ | 2,350 cm³ | same |
| Second moment, minor (Iz) | 59,800 cm⁴ | 59,800 cm⁴ | same |
| Plastic modulus, minor (Wpl,z) | 3,070 cm³ | 3,070 cm³ | same |
| Radius of gyration, minor (iz) | 17.5 cm | 17.5 cm | same |
| Torsion constant (It) | 120,000 cm⁴ | 120,000 cm⁴ | same |
CHS 508×12.5 to BS EN 10210-2:2006; CF CHS 508×12.5 to BS EN 10219-2:2006. Difference is expressed relative to CF CHS 508×12.5.
How to choose between them
On stiffness, CF CHS 508×12.5 has the larger second moment of area: 59,800 cm⁴ against 59,800 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 (20.1 against 20.1 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.