SHS 300×300×12.5 vs CF SHS 300×300×12.5
SHS 300×300×12.5 is an SHS Hot-finished section from the UK Blue Book (SCI P363); CF SHS 300×300×12.5 is the closest equivalent in the UK Blue Book (SCI P363). SHS 300×300×12.5 carries more bending: 1530 cm³ of plastic modulus against 1450 cm³, 5.5% more. CF SHS 300×300×12.5 is the lighter of the two at 108 kg/m against 112 kg/m, a saving of 3.7% on steel weight. Both are about 300 mm deep, so either fits the same construction zone.
| Property | SHS 300×300×12.5 SHS Hot-finished | CF SHS 300×300×12.5 SHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 112 kg/m | 108 kg/m | +3.7% |
| 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 | 142 cm² | 137 cm² | +3.6% |
| Second moment, major (Iy) | 19,400 cm⁴ | 18,300 cm⁴ | +6.0% |
| Plastic modulus, major (Wpl,y) | 1,530 cm³ | 1,450 cm³ | +5.5% |
| Elastic modulus, major (Wel,y) | 1,300 cm³ | 1,220 cm³ | +6.6% |
| Second moment, minor (Iz) | 19,400 cm⁴ | 18,300 cm⁴ | +6.0% |
| Plastic modulus, minor (Wpl,z) | 1,530 cm³ | 1,450 cm³ | +5.5% |
| Radius of gyration, minor (iz) | 11.7 cm | 11.6 cm | +0.9% |
| Torsion constant (It) | 30,300 cm⁴ | 30,600 cm⁴ | -1.0% |
SHS 300×300×12.5 to BS EN 10210-2:2006; CF SHS 300×300×12.5 to BS EN 10219-2:2006. Difference is expressed relative to CF SHS 300×300×12.5.
How to choose between them
On stiffness, SHS 300×300×12.5 has the larger second moment of area: 19,400 cm⁴ against 18,300 cm⁴, a difference of 6.0%. 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 (13.7 against 13.4 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 300×300×12.5 is the stronger section and CF SHS 300×300×12.5 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.