SHS 150×150×6.3 vs CF SHS 140×140×8
SHS 150×150×6.3 is an SHS Hot-finished section from the UK Blue Book (SCI P363); CF SHS 140×140×8 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 192 cm³ against 194 cm³ of plastic modulus, a difference of 1.0%. SHS 150×150×6.3 is the lighter of the two at 28.1 kg/m against 31.4 kg/m, a saving of 10.5% on steel weight. SHS 150×150×6.3 is deeper, 150 mm against 140 mm, which matters where the floor zone is tight.
| Property | SHS 150×150×6.3 SHS Hot-finished | CF SHS 140×140×8 SHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 28.1 kg/m | 31.4 kg/m | -10.5% |
| Depth | 150 mm | 140 mm | +7.1% |
| Width | 150 mm | 140 mm | +7.1% |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 35.8 cm² | 40 cm² | -10.5% |
| Second moment, major (Iy) | 1,220 cm⁴ | 1,130 cm⁴ | +8.0% |
| Plastic modulus, major (Wpl,y) | 192 cm³ | 194 cm³ | -1.0% |
| Elastic modulus, major (Wel,y) | 163 cm³ | 161 cm³ | +1.2% |
| Second moment, minor (Iz) | 1,220 cm⁴ | 1,130 cm⁴ | +8.0% |
| Plastic modulus, minor (Wpl,z) | 192 cm³ | 194 cm³ | -1.0% |
| Radius of gyration, minor (iz) | 5.85 cm | 5.3 cm | +10.4% |
| Torsion constant (It) | 1,910 cm⁴ | 1,900 cm⁴ | +0.5% |
SHS 150×150×6.3 to BS EN 10210-2:2006; CF SHS 140×140×8 to BS EN 10219-2:2006. Difference is expressed relative to CF SHS 140×140×8.
How to choose between them
On stiffness, SHS 150×150×6.3 has the larger second moment of area: 1,220 cm⁴ against 1,130 cm⁴, a difference of 8.0%. 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 of steel, SHS 150×150×6.3 is the more efficient section: 6.8 against 6.2 cm³ per kg/m, 10.6% better. Over a floor of repeated beams that difference is real tonnage, though it is often outweighed by whichever section the fabricator can actually source.
In short, CF SHS 140×140×8 is the stronger section and SHS 150×150×6.3 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.