UC 203×203×100 vs HE 200 M
UC 203×203×100 is an UC section from the UK Blue Book (SCI P363); HE 200 M is the closest equivalent in the European (Continental) range. They are close to interchangeable in bending: 1150 cm³ against 1140 cm³ of plastic modulus, a difference of 0.9%. UC 203×203×100 is the lighter of the two at 99.6 kg/m against 103 kg/m, a saving of 3.3% on steel weight. UC 203×203×100 is deeper, 228.6 mm against 220 mm, which matters where the floor zone is tight.
| Property | UC 203×203×100 UC | HE 200 M HE | Difference |
|---|---|---|---|
| Mass | 99.6 kg/m | 103 kg/m | -3.3% |
| Depth | 228.6 mm | 220 mm | +3.9% |
| Width | 210.3 mm | 206 mm | +2.1% |
| Web thickness | 14.5 mm | 15 mm | -3.3% |
| Flange thickness | 23.7 mm | 25 mm | -5.2% |
| Area | 127 cm² | 131 cm² | -3.1% |
| Second moment, major (Iy) | 11,300 cm⁴ | 10,600 cm⁴ | +6.6% |
| Plastic modulus, major (Wpl,y) | 1,150 cm³ | 1,140 cm³ | +0.9% |
| Elastic modulus, major (Wel,y) | 988 cm³ | 967 cm³ | +2.2% |
| Second moment, minor (Iz) | 3,680 cm⁴ | 3,650 cm⁴ | +0.8% |
| Plastic modulus, minor (Wpl,z) | 534 cm³ | 543 cm³ | -1.7% |
| Radius of gyration, minor (iz) | 5.39 cm | 5.27 cm | +2.3% |
| Torsion constant (It) | 210 cm⁴ | 258 cm⁴ | -18.6% |
UC 203×203×100 to BS EN 10365:2017; HE 200 M to EN 10365 · Continental Steel. Difference is expressed relative to HE 200 M.
How to choose between them
On stiffness, UC 203×203×100 has the larger second moment of area: 11,300 cm⁴ against 10,600 cm⁴, a difference of 6.6%. 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, UC 203×203×100 is the more efficient section: 11.5 against 11.1 cm³ per kg/m, 4.3% 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. UC sections are specified to BS EN 10365:2017 and HE to EN 10365 · 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 3.3% weight.
In short, UC 203×203×100 is the stronger section and UC 203×203×100 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.