PV Mounting C Channel Steel: Sizes, Materials and How to Specify the Section

Release Tme: 2026-10-21

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C channel — also called C-section, C purlin, and in its smaller sizes strut channel — is the cold-formed open section most photovoltaic mounting frames are built from. GNEE STEEL makes the section.

How the Section Is Made

The route is short: coated steel coil is slit to the developed width, run through a roll-forming mill, punched if the drawing calls for holes or slots, cut to length and bundled.

Every stand in the mill bends the strip a little further. The number and arrangement of those passes — not the steel grade — decides how tight the corner radius comes out and how much the coating is stretched at each fold. A section rolled in too few passes is where corner cracking and twist come from, and neither shows up on a drawing.

Reading the Designation

A callout such as C100 × 50 × 20 × 2.5 reads as web height, flange width, return lip, and thickness, all in millimetres. The lip is what turns a plain angle into a C: it stiffens the free edge of the flange and gives the section most of its resistance to local buckling.

Section	Web × flange × lip (mm)	Thickness range (mm)	Where it usually turns up
C41 × 41	41 × 41	1.5–2.5	Light rooftop rails, module support runs
C80 × 40 × 15	80 × 40 × 15	1.5–2.5	Rooftop rails, light ground-mount members
C100 × 50 × 20	100 × 50 × 20	2.0–3.0	Ground-mount rails and posts
C120–C160 × 50–60 × 20	120–160 × 50–60 × 20	2.5–3.0	Longer spans, heavier wind or snow regions

These are the sizes most often requested. We also roll to a drawing. The section is only standard to the extent your design makes it standard.

One thing to know before changing a size: the developed width decides which coil width the mill needs. A small change to the flange or the lip can push an order onto a different coil width, or onto slitting with the edge waste that comes with it. If you are considering a section change to save steel, send both drawings.

The Steel Underneath

Base material is normally Q235B or Q355B under GB/T, with EN 10346 grades S250GD through S550GD, AS 1397 G350 and G550, and ASTM A653 SS Grade 50 and 80 available for projects written to those standards. Cold-formed sections are produced to GB/T 6725.

Two details cause most of the friction at quotation stage.

Total thickness or base metal thickness. A section called 2.5 mm is usually sold on total thickness, coating included. A Z275 coating adds roughly 20 µm per side, so the steel underneath is nearer 2.46 mm. State which one your drawing is dimensioned on.

Weight basis. Sections are normally traded on theoretical weight calculated from the developed width and thickness, not weighed on a bridge.

Frequently Asked Questions

1. Do you supply complete mounting systems?
No. We produce the C channel section, and where a customer wants it, we punch and cut it to their drawing. System design, assembly and installation sit with the racking manufacturer or the EPC.

2. Can you punch holes and slots to our pattern?
Yes. Send the pattern and the pitch tolerance. Hole pitch accumulates over a length, so a small error per pitch becomes a real misalignment by the far end of a six-metre section.

3. What lengths do you ship, and is there a trial quantity?
Standard lengths and cut-to-length are both available, and trial quantities are accepted for a new section. Send the drawing and we will confirm tooling and schedule.

Send us the section drawing, the grade, the coating and the lengths. We will confirm what we can roll from stock coil and what needs tooling, and quote on a stated thickness and weight basis so your numbers reconcile with ours.

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Choosing Steel Grade by PV Mounting Member: Posts, Rails, Braces and Base Plates

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