The ABCs of Structural Steel

Structural Steel is an important building material characterized by its shape and cross-section, as well as its mechanical and chemical qualities. Structural Steel includes:

• Angles
• Beams
• Channels

Structural Steel Shapes at a Glance

The shape of structural steel affects more than appearance. It changes how the material carries weight, how easily it connects to other pieces, and where it performs best on a job.

• Structural steel beams are built for span. Their wide flanges and central web help carry weight across open areas, which is why they are often used under floors, roofs, platforms, and other load-bearing sections.
• Channels are useful when one side needs to stay open. Their shape makes them easier to fasten to flat surfaces, tuck into frames, or use along edges where a full beam would be too bulky.
• Angles are often used when a project needs a corner, edge, brace, or reinforcement point. Their L-shape gives fabricators a simple way to add strength without adding much material.
• HSS tubing works well when a project needs strength, stiffness, and resistance to twisting. It comes in square, rectangular, and round profiles, including common options like square steel tubing and round structural tubing. Its closed shape makes it useful for posts, columns, railings, frames, bracing, and exposed designs where appearance also matters.

Structural Angle

Structural Angle Terms

Leg (Flange) Size: The measurement of each leg (see “A & B” in diagram).
Leg (Flange) Thickness: The thickness of the leg (“C”).
Other terms: Fillet radius: The curved portion, where the inside transition between the web and flange occurs, is called a fillet. The radius of the fillet is called the fillet radius (not always provided).

A structural angle is a steel bar that has an L-shaped cross section. It is a piece of structural iron or steel in the form of a 90-degree angle. It is ideal for all structural applications, general fabrication, and repairs. This item can have equal sized legs (or flanges); this is typically known as equal leg angle. Legs (or flanges) that are differently sized are typically known as unequal leg angle.

The size measurement of the structural angle is commonly specified using the length of each leg (flange) and the thickness of the leg (flange). Dimensions in North America are typically in inches, and in the UK, in millimeters.

Hollow Structural Steel Tube

HSS Rectangular Tube and Square Tube Terms

Outside Dimensions: The outer measurement of each side (see “A & B” in the diagrams below).
Wall Thickness: The thickness of the tube wall (“C”).

HSS Round Tube Terms

Outside Diameter: The measurement of the outer diameter of the tube (see “A” in the diagram below).
Wall Thickness: The thickness of the tube wall (“B”).

Hollow Structural Steel (HSS) Tubing has become an essential component of the construction industry. It is also used to a great extent in the fabrication of enclosures, automobiles, and many other structural applications. HSS Tubes are produced in three shapes – round, square, and rectangular. They are available in a broad range of sizes and gauges. Some of the benefits of HSS tubes are

• A high strength-to-weight ratio (less weight-per-foot)
• Uniform strength
• High resistance to torsional loading (excellent choice for bracing)
• Increased formability
• Less resistance to air or water flow
• Easier in fitting mating parts together (no notching)
• Particularly well suited for compression column applications

HSS Tube is commonly specified using the outside size measurements and the tube wall thickness (square tube example: 2.000” x 2.000″ x 0.250” wall / round tube example: 3.000” Dia. x 0.250” wall).

Structural Beam

Structural Beams come in various shapes and sizes, so it is important to use the correct terminology when measuring.

Beam Terms

Beam Depth: The distance from the top and bottom surface of the steel (see “A” in diagram).
Flange Width: The top and bottom flat horizontal sections width (“B”).
Flange Thickness: The thickness of the top and bottom flat horizontal sections (“C”).
Web Thickness: The thickness of the vertical center section of a steel beam (“D”).
Fillet radius: The curved portion, where the inside transition between the web and flange occurs, is called a fillet. The radius of the fillet is called the fillet radius (not always provided).

Structural Beams are also known as I-beams, H-beams, and W-beams for the wider flanged versions. Some construction companies refer to them as Universal Beams or Rolled Steel Joists (RSJ). Typically they are used in the construction of buildings for structural support. The part of the Structural Beam that provides resistance to shear forces (breaking, tearing apart, or collapsing) is the web, while the flanges resist the bending movement of the section.

In Canada and the United States, steel I-beams are commonly specified using the depth (in inches) and weight of the beam (in pounds per foot). For example, a “4 x 13” I-beam is approximately 4 inches in depth (the measurement taken from the outer face of the first flange to the outer face of the opposite flange). This beam would weigh approximately 13 pounds per foot (note that wide flange beams can often vary from the mill listed depth measurement).

In Canada, certain steel I-beams may be available in metric, and while the depth and weight of the beam are in metric terms, the way they are measured is very similar. An example would be a “W250x33” beam, which is approximately 250 millimeters in depth and weighs approximately 33 kg per meter.

In the United Kingdom, Universal Beams or Columns are commonly specified with a code consisting of the depth (the measurement taken from the outer face of the first flange to the outer face of the opposite flange), the flange width, and the kilograms per meter. The code can end with the section type (Such as UB – Universal Beam or UC – Universal Column). All measurements are in metric. Therefore, a 152x152x23 UC would be a Universal Beam of approximately 152 millimeters in depth x 152 millimeters in width and weighing approximately 23 kilograms per meter.

Structural Channel

Channel Terms

Channel Depth: The distance from the top and bottom surface of the steel (see “A” in diagram).
Flange Height: The top and bottom flat horizontal sections (flanges) width (“B”).
Web Thickness: The thickness of the vertical center section of a channel (“C”).
Fillet radius: The curved portion, where the inside transition between the web and flange occurs, is called a fillet. The radius of the fillet is called the fillet radius (not always provided).

Steel Channel is a Hot Rolled product (typically grade ASTM A36). When looking at a cross section, it has a vertical web with horizontal top and bottom flanges. It comes in a wide varying range of sizes and web thicknesses. The shape of this type of product provides a great amount of structural strength, making it an ideal product for making frames and bracing. Typically it is used in the manufacturing of machinery, enclosures, and vehicles. It is also used in the construction of buildings for structural support. The Structural Channel, also known as a C-channel, is distinguished from the I-beam, H-beam, or W-beam, which has flanges on both sides of the web.

In Canada and the United States, steel channels are commonly specified using the depth (in inches) and weight of the channel (in pounds per foot). For example, a “6 x 13” channel is approximately 6 inches in depth and weighs approximately 13 pounds per foot.

In the UK, a steel channel (or C-section) can also be called a parallel flange channel. They are measured very similarly to universal beams: the depth, the flange width, and the kilograms per meter.

The only exception to the above method in channel measurement would be U-Channel or Bar Channel, which are measured by the depth, then the flange height, and lastly the web thickness. Dimensions in North America are typically in inches, and in the UK, in millimeters.

Steel Channel has the following categories:

• Structural Channel – Used in varied construction and manufacturing projects.
• Ship & Car Channel – A set of sizes that were developed for use in the construction of Marine Vessels and Automobiles.
• Stair Stringer Channel – A set of sizes that were developed for use in the construction of Stair Casings
• U-Channel or Bar Channel – A set of smaller channel sizes (depth 0.750” minimum to 2.500” maximum).

Disclaimer: Please note this information is not to be used for design purposes, and in no event shall MSFFC be liable for any damages arising from the misuse of this information.

How to Choose the Right Structural Steel

Start With the Job It Needs to Do

Choosing the right structural steel starts with the purpose of the piece. Before comparing shapes, think about the load, span, connection points, location, and how the steel will be installed. These details often matter more than the shape name alone because they affect how the material will carry weight, connect to other parts, and perform once it is in place.

Match the Shape to the Load

For projects that need support across an open span, structural steel beams are often the starting point. For frames, brackets, bracing, and smaller supports, channels and angles may be easier to work with. For posts, columns, railings, and structures that need strength in more than one direction, HSS tubing may be the better fit.

Consider the Environment

The location of the project can affect which structural steel products make sense. Steel used indoors may not need the same finish as steel exposed to rain, moisture, road salt, or changing temperatures. Outdoor projects may benefit from galvanized steel, primer, paint, or another protective finish, so it helps to think about exposure before you order.

Plan for Fabrication and Handling

Think about how the steel will be cut, drilled, welded, or fastened, and how each piece will be moved and installed. Some structural steel products are easier to work with than others, and long or heavy pieces may need extra help or equipment to position safely. Planning these details early helps avoid awkward joints, extra cuts, and fit-up problems later. The pre-order checklist below covers the specific details to confirm.

What to Know Before Ordering Structural Steel

Before ordering structural steel, gather the details that affect cutting, fit, and delivery. This helps the supplier prepare the material correctly and reduces the chance of delays, wrong cuts, or extra work.

• Final dimensions: Confirm the exact lengths, widths, thicknesses, and quantities needed for each piece. Do not choose steel based on appearance alone, since two pieces can look similar but differ in thickness, weight, grade, and strength.
• Cutting requirements: Note which pieces need to be cut to size and which lengths should be left standard. A beam that is too long may need extra cutting, while a piece cut too short may not work for the project.
• Hole locations: Mark where holes need to be drilled or punched, including spacing, diameter, and distance from the edge. A hole in the wrong spot can slow down installation or require rework.
• Connection details: Identify which pieces will be bolted, welded, or fitted together so the material can be prepared for the final layout. This is especially useful when structural steel fabrication is needed before installation.
• Finish and surface requirements: Confirm if the steel needs grinding, deburring, primer, paint prep, galvanizing, or another protective finish before use. Bare steel may be fine for some indoor uses, but outdoor or damp settings may need added protection.
• Pickup or delivery details: Check the length and weight of the structural steel products so you can plan the right vehicle, unloading area, and handling support. Long or heavy pieces may need special transport, lifting equipment, or more than one person to move safely.

FAQs

Can I choose structural steel beams by size alone?

No. Beam depth, flange width, web thickness, weight, span, load, and connection points all affect performance. A beam may look strong but still be wrong for the project if those details are not considered. The same beam can behave differently depending on how far it spans, how it is supported, and what type of load it carries. A beam supporting a simple platform is not the same as one supporting a floor, roof, or building frame. For load-bearing work, confirm the beam size with a licensed structural engineer or architect before ordering.

Do I need an engineer to choose structural steel beams?

For load-bearing work, it is best to confirm sizing with a licensed structural engineer or architect before buying structural steel beams. A supplier can help you compare available products, but beam selection depends on more than length and appearance. Span, load, spacing, support points, deflection, connection details, and local building requirements can all affect the correct size. This is especially important for floors, roofs, platforms, mezzanines, or building frames where the beam is part of the structure.

Why do hole locations matter when ordering structural steel?

Hole locations affect how the steel connects to other parts during installation. If a hole is too close to an edge, spaced incorrectly, or placed on the wrong side, the piece may not line up on site. Even a small mismatch can create problems with bolts, brackets, base plates, or adjoining steel pieces. This can lead to drilling changes, delays, extra labor, or additional structural steel fabrication work before the material can be installed.

What finish should I choose for structural steel?

The right finish depends on where the steel will be used. Bare steel may be fine for dry indoor projects. Steel used outdoors, near moisture, or in harsher conditions may need galvanizing, primer, paint, or another protective finish. The key is to confirm the finish early, especially if the steel will be cut, drilled, welded, or handled outdoors. Changing the finish later can add time, extra handling, or touch-up work.