SHS 140×140×7.1 vs SHS 150×150×6.3
SHS 140×140×7.1 is an SHS Hot-finished section from the UK Blue Book (SCI P363); SHS 150×150×6.3 is the closest equivalent in the European (Continental) range. They are close to interchangeable in bending: 184 cm³ against 185 cm³ of plastic modulus, a difference of 0.5%. SHS 150×150×6.3 is the lighter of the two at 27.4 kg/m against 29.2 kg/m, a saving of 6.6% 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 140×140×7.1 SHS Hot-finished | SHS 150×150×6.3 SHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 29.2 kg/m | 27.4 kg/m | +6.6% |
| Depth | 140 mm | 150 mm | -6.7% |
| Width | 140 mm | 150 mm | -6.7% |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 37.2 cm² | 34.8 cm² | +6.9% |
| Second moment, major (Iy) | 1,090 cm⁴ | 1,174 cm⁴ | -7.2% |
| Plastic modulus, major (Wpl,y) | 184 cm³ | 185 cm³ | -0.5% |
| Elastic modulus, major (Wel,y) | 155 cm³ | 156 cm³ | -0.6% |
| Second moment, minor (Iz) | 1,090 cm⁴ | 1,174 cm⁴ | -7.2% |
| Plastic modulus, minor (Wpl,z) | 184 cm³ | 185 cm³ | -0.5% |
| Radius of gyration, minor (iz) | 5.4 cm | 5.8 cm | -6.9% |
| Torsion constant (It) | 1,710 cm⁴ | 1,922 cm⁴ | -11.0% |
SHS 140×140×7.1 to BS EN 10210-2:2006; SHS 150×150×6.3 to EN 10219 · Continental Steel. Difference is expressed relative to SHS 150×150×6.3.
How to choose between them
On stiffness, SHS 150×150×6.3 has the larger second moment of area: 1,174 cm⁴ against 1,090 cm⁴, a difference of 7.2%. 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 6.3 cm³ per kg/m, 6.7% 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.
These come from different catalogues, so treat the swap as a design change rather than a like-for-like substitution. SHS Hot-finished sections are specified to BS EN 10210-2:2006 and SHS Cold-formed to EN 10219 · Continental Steel; the steel grades, tolerances and available lengths differ, connection details and bolt gauges are set out differently, and the two are rarely both stocked in the same market. Check availability before changing a section on a drawing to save 6.6% weight.
In short, SHS 150×150×6.3 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.