SHS 260×260×7.1 vs CF SHS 250×250×8
SHS 260×260×7.1 is an SHS Hot-finished section from the UK Blue Book (SCI P363); CF SHS 250×250×8 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 674 cm³ against 676 cm³ of plastic modulus, a difference of 0.3%. SHS 260×260×7.1 is the lighter of the two at 56 kg/m against 59.1 kg/m, a saving of 5.2% on steel weight. SHS 260×260×7.1 is deeper, 260 mm against 250 mm, which matters where the floor zone is tight.
| Property | SHS 260×260×7.1 SHS Hot-finished | CF SHS 250×250×8 SHS Cold-formed | Difference |
|---|---|---|---|
| Mass | 56 kg/m | 59.1 kg/m | -5.2% |
| Depth | 260 mm | 250 mm | +4.0% |
| Width | 260 mm | 250 mm | +4.0% |
| Web thickness | 0 mm | 0 mm | same |
| Flange thickness | 0 mm | 0 mm | same |
| Area | 71.3 cm² | 75.2 cm² | -5.2% |
| Second moment, major (Iy) | 7,570 cm⁴ | 7,230 cm⁴ | +4.7% |
| Plastic modulus, major (Wpl,y) | 674 cm³ | 676 cm³ | -0.3% |
| Elastic modulus, major (Wel,y) | 582 cm³ | 578 cm³ | +0.7% |
| Second moment, minor (Iz) | 7,570 cm⁴ | 7,230 cm⁴ | +4.7% |
| Plastic modulus, minor (Wpl,z) | 674 cm³ | 676 cm³ | -0.3% |
| Radius of gyration, minor (iz) | 10.3 cm | 9.8 cm | +5.1% |
| Torsion constant (It) | 11,600 cm⁴ | 11,600 cm⁴ | same |
SHS 260×260×7.1 to BS EN 10210-2:2006; CF SHS 250×250×8 to BS EN 10219-2:2006. Difference is expressed relative to CF SHS 250×250×8.
How to choose between them
On stiffness, SHS 260×260×7.1 has the larger second moment of area: 7,570 cm⁴ against 7,230 cm⁴, a difference of 4.7%. 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 260×260×7.1 is the more efficient section: 12.0 against 11.4 cm³ per kg/m, 5.2% 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 250×250×8 is the stronger section and SHS 260×260×7.1 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.