Two steel sections turn up on most residential and light-commercial drawings in Brisbane: the parallel flange channel (PFC) and the universal beam (UB). Both are hot-rolled structural steel and both carry load, but they are shaped differently, fix differently and suit different parts of a build. Knowing the difference makes it easier to read your engineer’s schedule and to order the right stock the first time.
What a PFC is
A parallel flange channel is a C-shaped section: a flat web with two flanges running off one side. The flat back is its biggest practical advantage. It sits hard against timber, masonry or another steel member, so it is easy to bolt through and easy to pack. That is why PFCs are common as lintels over widened openings, as bearers fixed alongside timber, and as edge members where one face needs to finish flush.
What a UB is
A universal beam is the familiar I-section: a central web with a flange on each side, symmetrical top to bottom and left to right. Because the material sits evenly around the centre, a UB is efficient in bending and stable for its weight, which is why it is the usual choice when a beam has to span further or carry more, such as a floor beam where a load-bearing wall is coming out.
How the choice is actually made
On any structural job the section, size and length come from your engineer’s design, not from a rule of thumb. The engineer weighs the span, the loads above, how the member is restrained and how it connects at each end. What you can do is understand why a particular section has been specified:
- Fixing and fit: a PFC’s flat back suits members that bolt to something alongside them.
- Span and load: a UB’s symmetrical shape usually suits longer, heavier spans.
- Space: ceiling depth and wall thickness can decide between a deeper or a wider section.
- Finish: where the steel sits (inside, under a deck, near the bay) affects the coating it needs.
If you are unsure what a callout on your drawings means, ask before you order. A beam that is the right section but the wrong length or finish costs just as much time on site as the wrong beam.
Ordering from Ace Posts and Beams
We hold parallel flange channels and universal beams at our Eagle Farm yard and cut them to the lengths on your schedule, so what arrives on site matches the drawings. Send us the schedule or the member list and we will quote the sections, lengths and finish. See our steel beams in Brisbane page for what we stock, or send us your enquiry.