Structural steel is steel that forms the frame itself: wide-flange beams, columns, HSS tube, channels, angles and plate, bolted or welded together. Rebar (reinforcing bar) is deformed steel bar cast inside concrete, where it carries the tension that concrete can't. Structural steel is designed to CSA S16 and is usually made to CSA G40.21 or ASTM grades. Rebar is made to CSA G30.18 and designed together with the concrete under CSA A23.3. They are both steel, but they are different products with different trades, drawings and standards.
Plenty of projects use both. A building can have a steel frame sitting on reinforced concrete footings, walls and slabs. Procut supplies both, so we see the boundary between them every day.
The short comparison
| Structural steel | Rebar (reinforcing steel) | |
|---|---|---|
| What it is | Rolled shapes, tube, plate and bars | Deformed round bar, 10M to 55M in Canada |
| How it carries load | On its own, as beams, columns and braces | Only inside concrete, as part of a composite member |
| Main design standard | CSA S16, Design of steel structures | CSA A23.3, Design of concrete structures |
| Material standard | CSA G40.21, ASTM A992, A36, A572, A500 | CSA G30.18 |
| Common grades | 350W, 345WM, 300W, A992 | 400W, 500W |
| Construction standard | CSA S16 and the welding standards | CSA A23.1, concrete materials and construction |
| Drawings | Shop drawings and erection drawings | Bar lists and placing drawings |
| Fabrication | Cut, drilled, fitted and welded into members | Cut and bent to shape, tagged and bundled |
| Joining | Bolts and welds | Lap splices, mechanical couplers, occasionally welding |
| Installed by | Steel erectors | Rodbusters (reinforcing ironworkers) |
The 2024 Ontario Building Code points to CSA S16 for structural steel and CSA A23.3 for reinforced concrete in its Part 4 design requirements, and it references CSA G40.21 and CSA G30.18 as the material standards.
How each one carries load
Structural steel works alone. A W-shape beam has flanges and a web shaped to resist bending. A column resists compression and buckling. An HSS brace carries tension and compression. Each member is designed for the forces it will see, then connected to the next member with bolts or welds. Once erected and connected, the frame stands on its own.
Rebar works in partnership. Concrete is strong in compression but weak in tension, and it cracks. Rebar is placed where tension will develop (the bottom of a beam or slab between supports, the top over supports, both faces of a wall) and the concrete is cast around it. The ribs (deformations) on the bar grip the concrete so the two act together. A single bar lying on the ground has almost no bending stiffness. Inside a properly designed concrete section, it makes a beam, slab or footing possible.
That is why comparing "strength" between the two misleads. Grade 400W rebar has a higher minimum yield (400 MPa) than typical 350W structural steel (350 MPa), but the bar alone can't do the job of a beam. Our article on rebar grades in Canada covers 400W and 500W in detail.
Different products, made and certified differently
Structural steel comes as shapes and plate rolled at a mill, or as tube formed from strip. Each shape has a designation (W250x33, HSS 102x102x6.4, C200x17, L102x102x9.5) and a grade. Common grades include CSA G40.21 300W and 350W for plate, channels and angles, ASTM A992 or CSA G40.21 345WM for wide-flange shapes, and 350W or ASTM A500 for HSS.
Rebar comes in standard metric sizes named by approximate diameter: 10M, 15M, 20M and up to 55M. The size tells you the area and mass. A 15M bar has a nominal area of 200 mm² and weighs 1.570 kg/m. The grade (usually 400W or 500W, where W means weldable) is rolled onto the bar. See types of rebar in Canada for coated and GFRP options.
What about "structural steel bars"? Flat bar, round bar and square bar used in steel fabrication are structural steel products, made to grades such as CSA G40.21 300W or 350W. A smooth round bar is not rebar, and rebar is not a substitute for structural bar in welded brackets, lifting lugs or frames.
Different drawings, shops and crews
The two materials follow parallel but separate paths from design to site.
Structural steel path:
- The engineer issues structural drawings showing members, sizes and loads.
- A steel detailer prepares shop drawings for each piece and erection drawings showing where they go.
- The fabricator cuts, drills, fits and welds the members. In Canada, companies welding structural steel designed to CSA S16 need certification by the Canadian Welding Bureau to CSA W47.1.
- Steel is delivered and erected by a steel erection crew, then bolted and field welded.
Rebar path:
- The engineer issues structural drawings showing bar sizes, spacing, cover and laps.
- A rebar detailer prepares bar lists and placing drawings, usually following the RSIC Manual of Standard Practice.
- The rebar fabricator cuts and bends bars to the standard shapes, then tags and bundles them by location.
- Bars are delivered and placed and tied by a rodbusting crew before the concrete pour.
Welding is a good example of how separate these are. Welding of reinforcing bar is covered by CSA W186, not the structural steel welding standards, so a shop certified to weld beams isn't automatically qualified to weld rebar. Our weldable rebar guide explains when rebar welding is allowed.
Where structural steel and rebar meet
The two systems connect at specific points, and these are the details that cause the most coordination problems:
- Anchor rods and base plates. Steel columns sit on base plates bolted to anchor rods cast into concrete footings or piers. The rods have to land in the right place among the footing rebar. See embedding steel posts vs base plates.
- Embed plates. Steel plates with welded studs or anchors cast into concrete walls or slabs, so steel beams or ledgers can be welded or bolted on later.
- Beam pockets and bearing. Steel beams bearing on concrete or masonry walls need the right bearing length and sometimes a bearing plate.
- Composite floors. Steel beams with welded shear studs and a concrete slab on steel deck, where the slab is reinforced with rebar or mesh.
- Fire and corrosion. Concrete cover protects rebar from fire and corrosion. Exposed structural steel may need its own fire protection or coatings. See concrete cover for rebar for the CSA A23.1 cover rules.
When one supplier handles both packages, these interfaces are easier to coordinate, because the people detailing the anchor rods and the people detailing the footing bars can talk to each other directly.
Which one does your project need?
You don't choose between them so much as use each where it fits:
- Foundations, slabs, walls and concrete structures need rebar (or another reinforcement the engineer approves).
- Beams over openings, basement beams and posts, steel frames, mezzanines and canopies are structural steel.
- Most commercial and many residential buildings need both: rebar in the concrete below, structural steel above or within it.
In a house, for example, the footings and foundation walls may contain rebar, while the main beam carrying the floor across the basement is often a steel W-shape on steel posts. Whether a house footing needs rebar at all is a separate question for the designer: the Ontario Building Code's Part 9 footing rules don't require it for plain strip footings.
Both from one supplier
Procut supplies and fabricates both. On the rebar side we detail, cut and bend bar from 10M to 55M, including dowels and stirrups, and supply GFRP rebar. On the steel side we fabricate beams, posts, lintels, plates and channels in a CWB certified shop with in-house shop drawings. We deliver across the GTA and Ontario and can supply and install both.
Send your structural drawings for a free take-off and quote covering the rebar, the steel, or both. See our rebar products and steel products.
Frequently asked questions
Is rebar considered structural steel?
Not in the usual trade sense. Structural steel means rolled shapes, plate and tube that form a frame on their own, designed to CSA S16. Rebar is reinforcing steel that only works inside concrete, made to CSA G30.18 and designed with the concrete under CSA A23.3.
What is the difference between structural steel and reinforcing steel?
Structural steel members (beams, columns, HSS, channels, angles, plate) carry loads by themselves and are bolted or welded together. Reinforcing steel is deformed bar cast into concrete to carry tension and control cracking. They are different products, standards, trades and drawings.
Is rebar stronger than structural steel?
Common Canadian rebar grade 400W has a minimum yield of 400 MPa, higher than the 350 MPa of typical CSA G40.21 350W structural steel. But strength per kilogram isn't the point: a bar on its own has almost no bending stiffness. It only works as part of reinforced concrete.
Can rebar be used as a structural steel bar?
No. Rebar is made and certified for concrete reinforcement. Flat bar, round bar and other bars used in steel fabrication are structural steel bars made to grades such as CSA G40.21. Using rebar for brackets, lifting points or welded frames is a substitution an engineer would not normally accept.
