Universal beam (UB)
Universal beam (UB) is the deep-web hot-rolled I-section that does the heavy lifting in residential: lintels, ridge beams, garage headers. AS/NZS 3679.1, Grade 300.
Ask Chalkline about this →A universal beam (UB) is a hot-rolled steel I-section produced to AS/NZS 3679.1, with a deeper web relative to its flange width than a universal column (UC). UBs are designated by nominal depth in millimetres and mass per metre in kg/m, e.g. 250 UB 31.4 is a 250 mm deep beam weighing 31.4 kg/m. The full residential range commonly used is 150 UB through 530 UB; 200 UB to 360 UB covers most house-scale spanning work. Standard grade is Grade 300 (300 MPa minimum yield stress), supplied with mill certificates referencing AS/NZS 3679.1.
UBs are the volume-residential steel-spanning section. Typical uses:
- Lintels over wide openings where a timber LVL is not deep enough.
- Ridge beams on cathedral ceilings and exposed-frame extensions.
- Garage door headers spanning double-car openings (commonly 5.5 to 6.5 m).
- Beams over courtyard openings in alterations and additions.
- Steel goalposts in moment-frame portals on alterations where bracing is constrained.
The section is sized by the structural engineer to AS 4100 (Steel structures) and is welded or bolted into the frame by a structural steel fabricator. Drilling, cutting or coping a UB on site without engineer’s approval can invalidate the design and is a defect at frame inspection.
Universal beam vs universal column. Both are I-sections to AS/NZS 3679.1. The UB has a deeper web (depth >> flange width), suited to spanning. The UC has a near-square section profile (depth ≈ flange width), suited to short loaded columns. Substituting one for the other without an engineer’s mark-up is a structural defect.
Also known as: UB; rolled steel joist (older British terminology, now non-standard in AU); I-beam (a loose term that also covers UCs and PFCs).
Category: Materials.
Related
See also
Last updated: 2026-05-15. Verified: 2026-05-15. Quarterly review for currency.