SHS 300×300×6.3 vs CF SHS 300×300×6.3
SHS 300×300×6.3 is an SHS Hot-finished section from the UK Blue Book (SCI P363); CF SHS 300×300×6.3 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 809 cm³ against 795 cm³ of plastic modulus, a difference of 1.8%. They weigh essentially the same, 57.8 kg/m and 57 kg/m. Both are about 300 mm deep, so either fits the same construction zone.
| Property | SHS 300×300×6.3 SHS Hot-finished | CF SHS 300×300×6.3 SHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 57.8 kg/m | 57 kg/m | +1.4% |
| Depth | 300 mm | 300 mm | same |
| Width | 300 mm | 300 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 73.6 cm² | 72.6 cm² | +1.4% |
| Second moment, major (Iy) | 10,500 cm⁴ | 10,300 cm⁴ | +1.9% |
| Plastic modulus, major (Wpl,y) | 809 cm³ | 795 cm³ | +1.8% |
| Elastic modulus, major (Wel,y) | 703 cm³ | 689 cm³ | +2.0% |
| Second moment, minor (Iz) | 10,500 cm⁴ | 10,300 cm⁴ | +1.9% |
| Plastic modulus, minor (Wpl,z) | 809 cm³ | 795 cm³ | +1.8% |
| Radius of gyration, minor (iz) | 12 cm | 11.9 cm | +0.8% |
| Torsion constant (It) | 16,100 cm⁴ | 16,200 cm⁴ | -0.6% |
SHS 300×300×6.3 to BS EN 10210-2:2006; CF SHS 300×300×6.3 to BS EN 10219-2:2006. Difference is expressed relative to CF SHS 300×300×6.3.
How to choose between them
On stiffness, SHS 300×300×6.3 has the larger second moment of area: 10,500 cm⁴ against 10,300 cm⁴, a difference of 1.9%. 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 (14.0 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.