Hot-rolled steel C-channels in Canada are usually supplied to CSA G40.21 grade 350W or 300W, or to the US grades ASTM A36 or A572 Grade 50, and a single channel is often certified to more than one of these at once. The grades differ in minimum yield strength: 350 MPa for 350W, 345 MPa for A572 Grade 50, 300 MPa for 300W and 250 MPa for A36. The drawings set the grade. Your job when ordering is to make sure the mill certificate shows it.
This article covers the material. For channel dimensions and weights, see our C-channel size chart.
Channel grades at a glance
| Specification | Grade | Also written as | Minimum yield strength | Notes |
|---|---|---|---|---|
| CSA G40.21 | 350W | 50W | 350 MPa (about 50 ksi) | Common Canadian structural grade for shapes |
| CSA G40.21 | 300W | 44W | 300 MPa (about 44 ksi) | Lower-strength Canadian structural grade |
| ASTM A572 | Grade 50 | A572-50 | 345 MPa (50 ksi) | US high-strength low-alloy grade |
| ASTM A36 | Single grade | A36 | 250 MPa (36 ksi) | US carbon structural steel; tensile strength 400 to 550 MPa (58 to 80 ksi) |
A few things about the names:
- CSA grades are named by minimum yield in megapascals. 350W means 350 MPa minimum yield. The W means weldable steel.
- 44W and 50W are the older imperial names for 300W and 350W, based on yield in ksi. Canadian mills still list both: Algoma Steel's published plate grade list, for example, shows 44W (300W) and 50W (350W). You'll hear "44W" a lot in fabrication shops, especially for plate and flat bar.
- ASTM A36 and A572 are US specifications that are widely used in Canada, particularly on drawings from US designers and on steel that is rolled in the US.
- A T after a CSA grade (350WT, for example) means the steel has also been impact tested for toughness, which some projects require for cold-weather or dynamically loaded members.
Yield strength: what "C-channel yield strength" really means
People often search for "the" yield strength of C-channel. There isn't one. Yield strength belongs to the grade of steel, not the shape. The same C200x17 can be rolled from A36 steel with a 250 MPa minimum yield or from 350W with a 350 MPa minimum yield. The second is 40% stronger in yield, with the same dimensions.
What carries load is the combination of the grade and the section properties. A channel's bending resistance, roughly, is the yield strength multiplied by a section modulus from the steel tables, then reduced by factors in CSA S16 for things like lateral buckling and the channel's tendency to twist. That calculation is the engineer's job, not something to estimate from a yield number.
Two practical points follow:
- A higher grade does not make a channel stiffer. Every structural steel grade has essentially the same modulus of elasticity, about 200 GPa. If a channel ledger or lintel is sized by deflection (which is common for long, lightly loaded members), switching from A36 to 350W changes nothing. Only a deeper or heavier section reduces deflection.
- A lower grade can make a design fail. If an engineer designed a channel as 350W and it is supplied as A36-only steel, its yield strength is about 29% lower than assumed. That is why the mill certificate matters.
Multi-grade certification
Much hot-rolled structural steel sold in North America is produced to meet several specifications at once, and the mill test report lists every grade the steel satisfies. Nucor-Yamato, a US mill that ships into Canada, describes its wide-flange mill certificates as listing ASTM A992, ASTM A709 and CSA G40.21 grades together. Channel and angle can be multi-certified too, and which combinations you get depends on the mill. The certificate is the only reliable way to know.
For you, this means:
- Ask for the mill test certificate (MTC or MTR) when your project needs one. It shows the heat number, the grades certified, the measured yield and tensile strength, elongation and chemistry.
- Check that the specified grade appears on it. If the drawing says 350W, "A36" alone is not enough, even if the measured yield happens to be high. The certified grade is what counts.
- Keep the certificates with the job file. Inspectors, engineers and owners may ask for them, especially on commercial and institutional work.
What about wide-flange beams, HSS and angles?
Channels are one of several hot-rolled shapes, and each has its usual grades.
| Shape | Grades you'll usually see in Canada | More detail |
|---|---|---|
| W-shapes (wide-flange beams and columns) | ASTM A992, CSA G40.21 345WM or 350W, often multi-certified | Canadian W-shape chart |
| C and MC channels | CSA G40.21 300W or 350W, ASTM A36, A572 Grade 50 | This article |
| Angles | The same family of grades as channels | Same as channels |
| HSS (tube) | CSA G40.21 350W Class C or H, ASTM A500 Grade C | HSS steel grades |
| Plate | CSA G40.21 300W or 350W, ASTM A36, A572 Grade 50 | Steel plate grades |
345WM deserves a note. It is a CSA G40.21 grade added in the 2013 edition (the edition the 2024 Ontario Building Code references) to line up with ASTM A992, the US grade for wide-flange shapes, which has a 345 MPa (50 ksi) minimum yield and a capped yield-to-tensile ratio. Mills that roll for both markets can now certify one beam to both. You'll see 345WM mainly on wide-flange beams and columns, not on channels.
Hot-rolled vs cold-formed channels
Not every "C-channel" is a hot-rolled structural shape. Cold-formed channels are bent from flat sheet or strip: steel studs and track, many purlins and girts, and light "C-sections" sold for framing. They are much thinner, they are made to sheet steel specifications rather than the structural grades above, and in Ontario they are designed under a different standard. The 2024 Ontario Building Code requires structural steel members to conform to CSA S16 and cold-formed steel members to conform to CSA S136, the North American specification for cold-formed members.
So when a drawing shows C200x17, it means the hot-rolled channel, with a grade from the table above. A cold-formed C of the same outside size is not a substitute. The size chart linked above explains how to tell the two apart.
Which grade should you order?
The one on the drawings. Structural drawings or the general notes normally state the grade for each shape, for example "W-shapes to ASTM A992 or CSA G40.21 345WM; channels, angles and plate to CSA G40.21 350W". If your drawing shows a channel without a grade:
- For engineered work, ask the engineer. Don't assume.
- For non-structural items such as trim, guards for equipment, or brackets that carry no real load, the grade is usually less critical, but someone responsible for the design should still say so in writing.
- For substitution, a higher-strength grade can often replace a lower one, but the engineer confirms it. Weld procedures, bolt bearing and other details may be affected, and the reverse (lower grade in place of higher) is never automatic.
Ordering checklist for channel:
- Full designation, for example C250x23 (C10x15.3).
- Grade, exactly as specified.
- Whether you need mill test certificates.
- Cut lengths and quantities, or the shop drawings.
- Holes, copes, mitres, welded clips and finish.
Our guide on where to buy C-channel in Ontario walks through the ordering side in more detail.
Channel supplied to the right grade
We supply hot-rolled C-channels cut to length or fabricated to your drawings, with holes, copes and welded plates as detailed. Shop welding is CWB certified and shop drawings are prepared in-house, so the grade on your drawings carries through to the pieces that arrive on site.
Send your drawings or channel list for a free quote, or see the C-channels and other steel products we supply.
Frequently asked questions
What grade of steel is C-channel?
Hot-rolled C and MC channels in Canada are commonly supplied to CSA G40.21 grade 300W or 350W, or to ASTM A36 or A572 Grade 50, and it is often certified to more than one of these. The grade you need is the one on the structural drawings.
What is the yield strength of C-channel?
It depends on the grade, not the shape. CSA G40.21 350W has a minimum yield of 350 MPa, 300W has 300 MPa, ASTM A572 Grade 50 has 345 MPa (50 ksi) and ASTM A36 has 250 MPa (36 ksi).
Is A36 the same as 350W?
No. A36 is a US specification with a minimum yield of 250 MPa (36 ksi). CSA G40.21 350W is a Canadian grade with a minimum yield of 350 MPa. A channel certified only to A36 should not be used where 350W is specified without the engineer's approval.
Does a higher grade make a channel stiffer?
No. All structural steel grades have about the same stiffness (a modulus of elasticity of about 200 GPa), so a higher grade raises strength but does not reduce deflection. If deflection governs, you need a bigger or heavier section, not a stronger grade.
