CHS 273×8 vs CF CHS 273×8
CHS 273×8 is an CHS Hot-finished section from the UK Blue Book (SCI P363); CF CHS 273×8 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 562 cm³ against 562 cm³ of plastic modulus, a difference of 0.0%. They weigh essentially the same, 52.3 kg/m and 52.3 kg/m. Both are about 273 mm deep, so either fits the same construction zone.
| Property | CHS 273×8 CHS Hot-finished | CF CHS 273×8 CHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 52.3 kg/m | 52.3 kg/m | same |
| Depth | 273 mm | 273 mm | same |
| Width | 273 mm | 273 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 66.6 cm² | 66.6 cm² | same |
| Second moment, major (Iy) | 5,850 cm⁴ | 5,850 cm⁴ | same |
| Plastic modulus, major (Wpl,y) | 562 cm³ | 562 cm³ | same |
| Elastic modulus, major (Wel,y) | 429 cm³ | 429 cm³ | same |
| Second moment, minor (Iz) | 5,850 cm⁴ | 5,850 cm⁴ | same |
| Plastic modulus, minor (Wpl,z) | 562 cm³ | 562 cm³ | same |
| Radius of gyration, minor (iz) | 9.37 cm | 9.37 cm | same |
| Torsion constant (It) | 11,700 cm⁴ | 11,700 cm⁴ | same |
CHS 273×8 to BS EN 10210-2:2006; CF CHS 273×8 to BS EN 10219-2:2006. Difference is expressed relative to CF CHS 273×8.
How to choose between them
On stiffness, CF CHS 273×8 has the larger second moment of area: 5,850 cm⁴ against 5,850 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 (10.7 against 10.7 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.