The Steel Section Cheat Sheet Every Builder Can Use

If you work around construction long enough, you quickly realise that steel has its own language.

UB. UC. PFC. RHS. SHS.

At first glance, it can feel like someone dropped a handful of abbreviations into a toolbox and decided you should somehow know what they mean.

The good news is that you don't need to memorise every steel section in existence. You do need to understand what the common sections are, what makes them different and, most importantly, why a particular section might be specified for a particular application.

That distinction matters because steel selection isn't simply about choosing something that looks strong. Structural performance depends on the section, dimensions, grade, loads, support conditions, connections and design requirements.

So, if you're ordering steel for a project, think of this as a practical cheat sheet—not a replacement for engineering design.

Start With the Application

Before you ask for a particular steel section, ask yourself a more useful question:

What does this steel need to do?

Is it spanning between supports? Supporting a vertical load? Forming a frame? Creating a post? Providing a bracket or connection? Supporting roofing?

Your answer immediately narrows down the possibilities.

The National Construction Code identifies common structural steel abbreviations including UB, RHS, PFC, SHS and CHS and points structural steel design toward AS 4100.

That is a useful reminder that section selection is fundamentally an engineering decision.

In other words, don't choose a beam because it “looks beefy enough.” Your eyeballing skills may be excellent, but they haven't replaced structural calculations yet.

1. UB — Universal Beam

A Universal Beam (UB) is one of the familiar structural steel sections you'll encounter in building work.

Its I-shaped profile has a relatively deep web and wider flanges, making it suitable for applications where a beam needs to span and carry loads according to the relevant design.

You may encounter UBs in:

• Structural frames
• Beams
• Openings
• Support structures
• Building modifications

But here's the important part: you don't select a UB simply because you need “a beam.”

The required size depends on the structural design, span, loads, support conditions and other factors.

Harding Steel lists Universal Beams among its structural steel products available in Brisbane.

2. UC — Universal Column

A Universal Column (UC) is another common hot-rolled structural section.

As its name suggests, it is commonly associated with column applications, where vertical loads need to be transferred through a structural member.

You'll often encounter UC sections when discussing:

• Columns
• Posts
• Structural supports
• Frames

The distinction between UB and UC isn't simply about one being “horizontal” and the other “vertical.” The actual structural behaviour depends on how the member is designed and used.

The Australian Steel Institute's structural steel resources include both UB and UC sections within its open-section design information.

3. PFC — Parallel Flange Channel

Now we come to the parallel flange channel, commonly shortened to PFC.

A PFC has a channel-shaped profile with parallel flanges. This geometry gives it different structural characteristics from an I-shaped UB or UC.

PFC steel can be used in suitable structural and fabrication applications, including:

• Frames
• Supports
• Brackets
• Lintels and structural members where specified
• General fabrication

Harding Steel lists Parallel Flange Channel (PFC) as part of its Brisbane product range.

The key lesson is simple: don't treat PFC steel as interchangeable with every other structural section. Even when two sections have similar dimensions, their shape and structural properties can be different.

4. RHS — Rectangular Hollow Section

If you've worked on steel frames, you've probably come across rectangular hollow section steel, or RHS.

Unlike open sections such as UB and PFC, RHS is a hollow rectangular profile.

That makes RHS particularly useful for applications involving:

• Steel frames
• Posts
• Structural supports
• Fabrication
• Architectural steelwork
• General rectangular framing

The Australian Steel Institute provides section-property information specifically covering rectangular hollow sections and square hollow sections.

Harding Steel also lists Rectangular Hollow Section (RHS) within its product range.

Why RHS sections can be practical

One advantage of RHS sections is their enclosed profile.

You don't have the exposed open shape of a channel or I-section. Depending on the project, that can make RHS useful where a cleaner rectangular appearance or enclosed section is desirable.

But again, appearance shouldn't drive a structural decision.

If an engineer has specified a particular RHS size and grade, that's the specification you should follow.

5. SHS — Square Hollow Section

SHS stands for Square Hollow Section.

Think of it as the square counterpart to RHS.

The four equal sides give SHS its symmetrical shape, which can make it useful in suitable framing, posts and fabrication applications.

You might encounter SHS in:

• Steel frames
• Posts
• Balustrades
• Fabricated structures
• Architectural applications
• General steelwork

Harding Steel lists both SHS and RHS, giving customers access to different hollow-section profiles.

The Australian Steel Institute's hollow-section resources also distinguish between RHS and SHS and provide design information for these section families.

RHS vs SHS: What's the Practical Difference?

This is one of the most common questions.

The basic difference is the shape:

RHS: rectangular
SHS: square

That sounds almost too obvious, but the geometry affects how you use the section.

If you need a rectangular profile for a particular frame, RHS may suit the application. If equal dimensions on all sides are desirable, SHS may be more appropriate.

But don't turn this into a “RHS is better than SHS” debate.

There isn't a universal winner.

The appropriate section depends on the structural requirement, design and application.

6. Don't Forget Angles and Bars

The steel section conversation doesn't end with beams and hollow sections.

Your project may also require:

• Equal angles
• Unequal angles
• Flat bar
• Square bar
• Round bar
• Steel plate
• Steel sheet
• Pipe
• Purlins

These products can play very different roles.

An angle can be useful for brackets, frames and connections. Flat bar may suit fabrication and general steelwork. Square bar can be used in suitable fabrication applications.

Harding Steel's product range includes angles, flat bar, square bar, pipe, purlins, sheets, mesh and other steel products alongside structural sections.

This is why you should build your steel order around the actual project requirements, rather than simply asking for “some steel.”

A Simple Section Cheat Sheet

Here's a quick way to remember the main categories:

Remember: this is a general guide, not a structural design table.

The actual suitability of a section depends on the project.

Why Your Cut List Matters

Once you've identified the required sections from your plans or specifications, the next challenge is getting the material in useful lengths.

This is where a proper cut list can save headaches.

Instead of saying:

“I need some RHS.”

You might provide:

• RHS — specified size
• Quantity — 6 pieces
• Length — 2,400 mm each

That's much easier for a supplier to work with.

Harding Steel states that it can supply full mill lengths as well as cut-to-size steel, and customers can provide a cut list for specified lengths.

For busy builders, that can make the difference between a material delivery that is ready to work with and a pile of steel that still needs another afternoon of cutting.

Nobody has ever put “cut everything twice” on a project schedule.

Don't Choose Steel From a Photo

This sounds obvious, but it's worth saying.

A photograph can show you the shape of a steel section. It cannot tell you whether that section is structurally suitable for your project.

Two pieces of steel can look almost identical while having different:

• Dimensions
• Thicknesses
• Grades
• Section properties
• Design capacities

The Australian Steel Institute maintains design resources covering both open structural sections and hollow sections, reinforcing the importance of using appropriate technical information when steel is designed and specified.

So, if your project is structural, work from the drawings, engineering specifications and applicable standards.

Ask Your Steel Supplier Better Questions

When you contact a supplier, you don't need to sound like you've memorised an engineering textbook.

You just need to provide useful information.

Tell them:

1. What you're building
2. Which section has been specified
3. Required size and grade
4. Quantity
5. Required lengths
6. Whether cutting is required
7. Whether you need collection or delivery

If you're unsure about the product itself, explain the application and ask what information they need from you.

For builders and trades working around Brisbane, a local supplier can also make the logistics easier. Harding Steel operates from Geebung on Brisbane's northside and supplies structural and general steel products, including UB, UC, PFC, RHS and SHS.

Where the Cheat Sheet Has Limits

Here's where I should be clear about the limits of a general article like this.

I can explain what a parallel flange channel, RHS or PFC steel section is and where these products are commonly encountered. I cannot tell you that a particular section is structurally safe for your building without the necessary project information and professional design.

Things such as span, load, restraint, connections, member orientation, deflection and the surrounding structure can all affect the answer.

That's why a good supplier and a qualified structural professional have different but complementary roles.

Your supplier helps you source and prepare the material.

Your engineer determines what the structure requires.

Keeping those responsibilities separate is a good thing.

What This Means for Your Next Steel Order

The easiest way to make steel selection less confusing is to stop thinking of the products as a giant list of abbreviations.

Think of them as tools with different shapes and characteristics.

A UB isn't simply “big steel.”

A UC isn't simply “another beam.”

A PFC isn't just a smaller UB.

RHS sections aren't interchangeable with SHS just because both are hollow.

And rectangular hollow section steel isn't selected purely because it looks neat in a frame.

The shape, dimensions and specification exist for a reason.

The Future of Steel Selection

Steel ordering is becoming increasingly connected to digital drawings, detailed cut lists, fabrication workflows and better project planning. As these processes improve, you may have more precise information available before you even contact a supplier.

That could mean less waste, more accurate cutting and fewer last-minute surprises.

But the basic principle probably won't change.

You still need to choose the material according to what the structure is designed to do.

So the next time someone throws a list of UB, UC, PFC, RHS and SHS numbers at you, don't panic.

Start with the application.

Then check the specification.

Then order the right steel.

That three-step approach will get you much further than guessing—and probably save you from having a very awkward conversation with a tape measure.