Universal Beams (UB) and Universal Columns (UC) are the workhorse steel sections in South African construction. They look similar but are optimised for different jobs. Specifying the wrong one is a common cost error.
Key differences
- UB: tall, narrow, deep web — optimised for bending
- UC: roughly square cross-section — optimised for axial load
When to use a UB
- Floor beams
- Roof beams
- Lintels over openings
- Any horizontal member resisting bending
When to use a UC
- Columns
- Short stocky members carrying axial load
- Wall studs in steel-framed buildings
- Stub columns at beam supports
Why not always UC for compression?
UCs have similar flange and web sizes for buckling resistance in both axes — important for columns. UBs have deep narrow webs that buckle easily about the weak axis.
Common South African sizes
Universal Beams (UB)
- 127×76 UB 13 kg/m (small)
- 203×102 UB 23 kg/m (typical residential)
- 254×146 UB 31 kg/m (medium)
- 356×171 UB 51 kg/m (large residential / small commercial)
- 610×229 UB 113 kg/m (commercial)
- 914×419 UB 388 kg/m (heavy commercial)
Universal Columns (UC)
- 152×152 UC 30 kg/m (small)
- 203×203 UC 46 kg/m (typical residential)
- 254×254 UC 73 kg/m (commercial)
- 305×305 UC 97 kg/m (large)
- 356×406 UC 235–634 kg/m (very heavy)
Naming convention
e.g. "203×102×23 UB" = nominal depth × nominal width × kg per metre run.
What this means in practice
If your contractor proposes a UC where a UB is needed (or vice versa), the design is wrong. Engineers specifying for residential extensions almost always use UBs for horizontal members and UCs for any required posts.
MCFAR specifies appropriate steel sections on every project.
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Request a QuoteFrequently Asked Questions
What's the difference between UB and RSJ?
RSJ (Rolled Steel Joist) is older terminology, mostly superseded by UB. They are similar in appearance but different section properties.
Are PFC or RHS sections used for beams?
Yes — Parallel Flange Channels (PFC) for trimming and edge beams; Rectangular Hollow Sections (RHS) where appearance matters or torsion is significant.