SHS 90×90×4 vs CF SHS 90×90×4
SHS 90×90×4 is an SHS Hot-finished section from the UK Blue Book (SCI P363); CF SHS 90×90×4 is the closest equivalent in the UK Blue Book (SCI P363). SHS 90×90×4 carries more bending: 43.6 cm³ of plastic modulus against 42.6 cm³, 2.3% more. They weigh essentially the same, 10.7 kg/m and 10.5 kg/m. Both are about 90 mm deep, so either fits the same construction zone.
| Property | SHS 90×90×4 SHS Hot-finished | CF SHS 90×90×4 SHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 10.7 kg/m | 10.5 kg/m | +1.9% |
| Depth | 90 mm | 90 mm | same |
| Width | 90 mm | 90 mm | same |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 13.6 cm² | 13.3 cm² | +2.3% |
| Second moment, major (Iy) | 166 cm⁴ | 162 cm⁴ | +2.5% |
| Plastic modulus, major (Wpl,y) | 43.6 cm³ | 42.6 cm³ | +2.3% |
| Elastic modulus, major (Wel,y) | 37 cm³ | 36 cm³ | +2.8% |
| Second moment, minor (Iz) | 166 cm⁴ | 162 cm⁴ | +2.5% |
| Plastic modulus, minor (Wpl,z) | 43.6 cm³ | 42.6 cm³ | +2.3% |
| Radius of gyration, minor (iz) | 3.5 cm | 3.48 cm | +0.6% |
| Torsion constant (It) | 260 cm⁴ | 261 cm⁴ | -0.4% |
SHS 90×90×4 to BS EN 10210-2:2006; CF SHS 90×90×4 to BS EN 10219-2:2006. Difference is expressed relative to CF SHS 90×90×4.
How to choose between them
On stiffness, SHS 90×90×4 has the larger second moment of area: 166 cm⁴ against 162 cm⁴, a difference of 2.5%. 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 (4.1 against 4.1 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, SHS 90×90×4 is the stronger section and CF SHS 90×90×4 is the lighter one; where those are the same section, it is the clear choice, and where they are not, decide on whether your design is governed by capacity or by tonnage.