CHS 508×16 vs CF CHS 508×16
CHS 508×16 is an CHS Hot-finished section from the UK Blue Book (SCI P363); CF CHS 508×16 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 3870 cm³ against 3870 cm³ of plastic modulus, a difference of 0.0%. They weigh essentially the same, 194 kg/m and 194 kg/m. Both are about 508 mm deep, so either fits the same construction zone.
| Property | CHS 508×16 CHS Hot-finished | CF CHS 508×16 CHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 194 kg/m | 194 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 | 247 cm² | 247 cm² | same |
| Second moment, major (Iy) | 74,900 cm⁴ | 74,900 cm⁴ | same |
| Plastic modulus, major (Wpl,y) | 3,870 cm³ | 3,870 cm³ | same |
| Elastic modulus, major (Wel,y) | 2,950 cm³ | 2,950 cm³ | same |
| Second moment, minor (Iz) | 74,900 cm⁴ | 74,900 cm⁴ | same |
| Plastic modulus, minor (Wpl,z) | 3,870 cm³ | 3,870 cm³ | same |
| Radius of gyration, minor (iz) | 17.4 cm | 17.4 cm | same |
| Torsion constant (It) | 150,000 cm⁴ | 150,000 cm⁴ | same |
CHS 508×16 to BS EN 10210-2:2006; CF CHS 508×16 to BS EN 10219-2:2006. Difference is expressed relative to CF CHS 508×16.
How to choose between them
On stiffness, CF CHS 508×16 has the larger second moment of area: 74,900 cm⁴ against 74,900 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 (19.9 against 19.9 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.