C-channel steel is a structural steel section with a flat web and two flanges that point the same way, so its end view looks like a squared-off letter "C". Hot-rolled channels are made at a steel mill to the same structural grades as beams, and in Canada they're named by depth and mass, such as C200x17 (about 203 mm deep, 17 kg/m). Builders use them where one flat face needs to sit against something: stair stringers, opening frames, ledgers, lintels and bracing.
This guide covers what a channel is, how it differs from other steel shapes, and where you'll see it on a building. For sizes, weights and load tables, follow the links to our more detailed posts.
What C-channel looks like and what the parts are called
A channel has three parts:
- The web. The tall, flat plate. Its outside face is the "back" of the channel.
- Two flanges. Narrow plates along the top and bottom edges of the web, both projecting on the same side.
- The toes. The free edges of the flanges, pointing away from the web.
On standard hot-rolled channels, the inside faces of the flanges are tapered rather than parallel, and the corners where the flanges meet the web have rolled fillets. That's normal, and it's one way to tell a mill channel from a bent-up sheet product. Where bolts pass through a sloped flange, the detailer may call for bevelled washers so the nut sits square.
On Canadian drawings, channels are written with the letter C, the nominal depth in millimetres and the mass in kg/m. The same physical section has an imperial name too: a C200x17 is a C8x11.5. Standard Canadian channels run from C75 to C380. The C-channel size chart explains the naming and lists every standard size.
How a channel differs from beams and angles
Steel channel sits between the angle and the W-beam in the family of structural shapes.
| Shape | End view | Symmetry | Typical role |
|---|---|---|---|
| Angle (L) | L | None | Lintels, clips, bracing, frames |
| Channel (C, MC) | C | One axis | Stringers, opening frames, ledgers, girts |
| W-beam | I or H | Both axes | Beams and columns |
| HSS | Square, rectangle or round tube | Both axes | Posts, columns, bracing, frames |
The important difference is symmetry. A W-beam is symmetrical about its web, so a load applied through the web bends it straight down. A channel's flanges are all on one side, so the point through which a load must pass to avoid twisting (the shear centre) sits outside the web, behind the back face. Load a lone channel through its web and it wants to roll as well as bend.
In practice, designers deal with this by bracing the channel, pairing channels back to back or toe to toe, connecting the web to something stiff (a wall, a slab edge, a stair tread), or simply choosing a different shape for a long free-spanning beam. Our comparison of C-channel vs I-beam strength and span puts numbers on the difference.
Where C-channel is used in construction
Channels earn their place because of the flat back and the easy connections to the web and flanges. Common uses:
In houses and small buildings
- Steel stair stringers. Channel stringers with welded tread brackets or pans are one of the most common steel stair designs. The flat back faces the wall or the open side. See steel stair stringer sizes.
- Lintels and headers. A channel can carry masonry or framing over an opening, sometimes paired with an angle to support brick.
- Ledgers. A channel bolted to a foundation wall or beam can carry joists or decking.
- Trimmers around openings. Channels frame stair openings, skylights and chimney openings in steel or mixed floor systems.
In commercial and industrial buildings
- Floor and roof opening frames. Channels frame openings for ducts, hatches and rooftop units, sitting between the main beams.
- Equipment supports and platforms. Channels make tidy frames for mechanical units, tanks and catwalks.
- Girts and bracing. Light channels serve as wall girts that carry cladding, as struts and as secondary bracing.
- Slab edge and pour stop members. Channels and bent plates finish slab edges on steel framing.
- Built-up members. Two channels laced or plated together make a stiffer post, column or beam, a detail common in older buildings and still used for heavy or special members.
- Trailer frames, skids and machine bases. Outside buildings, channel is a staple for frames that need flat mounting faces.
Types of steel channel: C, MC and cold-formed
"Channel" covers more than one product, and ordering the wrong one is a common mistake.
- Standard C-channel. The hot-rolled section described above, made in the standard C sizes.
- MC (miscellaneous) channel. Also hot rolled, but with proportions outside the standard C series, often with wider or thicker flanges for the same depth.
- Cold-formed channel. Bent from thin sheet or strip at room temperature: steel studs, track, light C-purlins and similar. It has sharp, uniform-thickness bends with no fillets, and the 2024 Ontario Building Code sends cold-formed members to a different design standard (CSA S136) than hot-rolled structural steel (CSA S16). A cold-formed C is not a substitute for a hot-rolled C of the same outside size. The C-channel vs purlin and Z-channel post explains the difference.
- Strut channel. The slotted, lipped channel used to hang pipes and conduit is a separate product again.
- "U-channel". Sometimes just another name for C-channel, sometimes a formed or European section. Check before ordering.
What to watch for when using channel
A few practical points come up again and again:
- Orientation. Which way the toes face changes how the channel connects and how it carries load. The drawings should show it, and the fabricator needs to know.
- Twisting under load. A lone channel spanning freely with a load on top is the case most likely to be under-designed by guesswork. Use the size and bracing the designer specifies.
- Grade. Channels in Canada are usually supplied to CSA G40.21 300W or 350W, or ASTM A36 or A572, often multi-certified. If the drawing names a grade, it needs to arrive with a mill certificate.
- Corrosion. Channels used outdoors or in damp areas need a coating. Channel toes and the inside of the flanges can trap water, so detail drainage where the toes face up.
- Structural use needs a design. Channels used as stringers, lintels or beams are structural members. In Ontario that usually means a designer or engineer and a building permit.
How much load a particular channel can carry depends on span, bracing and how it's loaded. Our C-channel load capacity guide walks through the method.
Ordering C-channel cut and fabricated
To quote channel accurately, a fabricator needs the designation (for example C250x30), the grade if specified, lengths, which way the toes face at each connection, holes, copes, welded clips or plates, and the finish. We cut, drill and weld C-channels to order in our CWB certified shop, prime or galvanize them to suit, and deliver across the GTA and Ontario. For miscellaneous items such as stair stringers, we fabricate and deliver, and installation is by your installer or contractor.
Send your drawings or a cut list for a quote, or see the steel products we supply.
Frequently asked questions
What is C-channel used for in construction?
Hot-rolled C-channel is used for stair stringers, framing around floor and roof openings, lintels and headers, equipment supports, girts and bracing, ledgers at walls and slab edges, and built-up posts and beams made from two channels. It suits jobs where one flat face has to sit tight against a wall, a slab edge or another member.
What does C-channel look like?
It is a flat web with a flange along each edge, both flanges pointing the same way, so the end view looks like a squared-off letter C. The back of the web is flat. On standard hot-rolled channels the inside faces of the flanges are slightly sloped and the corners have rolled fillets.
Is C-channel the same as an I-beam?
No. An I-beam or W-beam has flanges on both sides of the web, so it is symmetrical and bends without twisting when loaded through the web. A channel has flanges on one side only, which leaves its shear centre outside the web, so it tends to twist under load unless it is braced, paired or connected to prevent it.
Is C-channel strong?
For its job, yes, but a channel is generally less efficient as a long-span beam than a W-shape of similar weight because of the twisting tendency and its narrow flanges. Channels are chosen for their flat back and convenient connections, not because they beat a beam on strength.
