SHS 350×350×8 vs CF SHS 350×350×8
SHS 350×350×8 is an SHS Hot-finished section from the UK Blue Book (SCI P363); CF SHS 350×350×8 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 1390 cm³ against 1370 cm³ of plastic modulus, a difference of 1.5%. They weigh essentially the same, 85.4 kg/m and 84.2 kg/m. Both are about 350 mm deep, so either fits the same construction zone.
| Property | SHS 350×350×8 SHS Hot-finished | CF SHS 350×350×8 SHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 85.4 kg/m | 84.2 kg/m | +1.4% |
| Depth | 350 mm | 350 mm | same |
| Width | 350 mm | 350 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 109 cm² | 107 cm² | +1.9% |
| Second moment, major (Iy) | 21,100 cm⁴ | 20,700 cm⁴ | +1.9% |
| Plastic modulus, major (Wpl,y) | 1,390 cm³ | 1,370 cm³ | +1.5% |
| Elastic modulus, major (Wel,y) | 1,210 cm³ | 1,180 cm³ | +2.5% |
| Second moment, minor (Iz) | 21,100 cm⁴ | 20,700 cm⁴ | +1.9% |
| Plastic modulus, minor (Wpl,z) | 1,390 cm³ | 1,370 cm³ | +1.5% |
| Radius of gyration, minor (iz) | 13.9 cm | 13.9 cm | same |
| Torsion constant (It) | 32,400 cm⁴ | 32,600 cm⁴ | -0.6% |
SHS 350×350×8 to BS EN 10210-2:2006; CF SHS 350×350×8 to BS EN 10219-2:2006. Difference is expressed relative to CF SHS 350×350×8.
How to choose between them
On stiffness, SHS 350×350×8 has the larger second moment of area: 21,100 cm⁴ against 20,700 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 (16.3 against 16.3 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.