Universal beams (UBs) and universal columns (UCs) are the two most common hot-rolled I-sections used in UK construction. They look similar, and both are often called RSJs, but they are shaped for different jobs. Here is a plain-English guide to telling them apart.
The short answer
- Universal beam (UB): deeper than it is wide, with relatively narrow flanges. Designed to span horizontally and resist bending.
- Universal column (UC): roughly as wide as it is deep (an “H” shape), with wider, thicker flanges. Designed to stand vertically and carry compression.
How UK sizes are written
Both sections are described by serial size and mass, for example 203 x 133 x 25 UB or 152 x 152 x 23 UC. The first number is the nominal depth in millimetres, the second is the nominal flange width, and the third is the mass in kilograms per metre. UK sizes follow BS 4-1, so the same designation means the same section from any UK stockholder.
A quick way to tell them apart on paper: if the first two numbers are close (152 x 152, 203 x 203) it is a column. If the depth is clearly bigger than the width (203 x 133, 254 x 146) it is a beam.
Where each one is used
- UBs: lintels and beams over knocked-through walls, rear extensions, loft conversions, floor joists and roof steels.
- UCs: posts and columns supporting beams, goalpost frames, and situations where headroom is limited and a shallow, stocky section is preferred.
Columns are sometimes used horizontally too, for example where an engineer needs a shallower section to keep a ceiling flush. That is a design decision, which is why the engineer’s drawing should always lead.
Which one do I need?
Your structural engineer will specify the exact section, length and any connection details such as end plates, bolt holes or padstones. Bring us the calculations or drawing and we can supply exactly what is specified, cut to length.
From our yard
We stock universal beams and universal columns in standard UK sizes, plus saw cutting, drilling and priming or galvanising.
This guide is general information only. The size and grade of any structural member must be specified by a qualified structural engineer or building control-approved design.
Not sure which section your engineer has specified? Upload your calculations and we’ll quote the exact beam or column sizes, cut to length and ready to go.