CHS 273×5 vs CF CHS 273×5
CHS 273×5 is an CHS Hot-finished section from the UK Blue Book (SCI P363); CF CHS 273×5 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 359 cm³ against 359 cm³ of plastic modulus, a difference of 0.0%. They weigh essentially the same, 33 kg/m and 33 kg/m. Both are about 273 mm deep, so either fits the same construction zone.
| Property | CHS 273×5 CHS Hot-finished | CF CHS 273×5 CHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 33 kg/m | 33 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 | 42.1 cm² | 42.1 cm² | same |
| Second moment, major (Iy) | 3,780 cm⁴ | 3,780 cm⁴ | same |
| Plastic modulus, major (Wpl,y) | 359 cm³ | 359 cm³ | same |
| Elastic modulus, major (Wel,y) | 277 cm³ | 277 cm³ | same |
| Second moment, minor (Iz) | 3,780 cm⁴ | 3,780 cm⁴ | same |
| Plastic modulus, minor (Wpl,z) | 359 cm³ | 359 cm³ | same |
| Radius of gyration, minor (iz) | 9.48 cm | 9.48 cm | same |
| Torsion constant (It) | 7,560 cm⁴ | 7,560 cm⁴ | same |
CHS 273×5 to BS EN 10210-2:2006; CF CHS 273×5 to BS EN 10219-2:2006. Difference is expressed relative to CF CHS 273×5.
How to choose between them
On stiffness, CF CHS 273×5 has the larger second moment of area: 3,780 cm⁴ against 3,780 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 (10.9 against 10.9 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.