What a C purlin is, and where it wins
A C purlin is a cold-formed channel: a web of height h, two equal flanges and a small stiffening lip. In a steel building it carries the roof sheet between frames as a roof purlin, or the wall cladding between columns as a wall girt. We roll nine C heights from C80 to C250 on three cold-forming lines.
C sections are the simpler of the two purlin families. Both flanges are the same width, so the profile is symmetric, it stacks flat, and it lands on a cleat as a plain butt joint. That makes C the default choice for wall girts, eave and edge members, and roofs where the runs are broken up by frames.
Where a C purlin is the right answer
- Short single spans. Typically 4.5 to 6 m at 1.2 to 1.5 m purlin spacing, where a plain butt joint is cheaper and faster on site than a lap.
- Wall girts. The flat face takes cladding directly and the fixing line stays straight along the wall.
- Eave beams, edge members and door headers. Straight, symmetric and easy to bolt to a bracket.
- Transport. C sections stack flat without the handed sorting that a nested Z run needs.
C80 to C250 · nominal dimensions
| Model | Web h | Flange b1 | Flange b2 | Lip c | Punching |
|---|---|---|---|---|---|
| C80 | 80 | 40 | 40 | 15 | No punching |
| C100 | 100 | 50 | 50 | 20 | 40 mm |
| C120 | 120 | 50 | 50 | 20 | Adjustable |
| C140 | 140 | 50 | 50 | 20 | Adjustable |
| C160 | 160 | 60 | 60 | 20 | Adjustable |
| C180 | 180 | 60 | 60 | 20 | Adjustable |
| C200 | 200 | 60 | 60 | 20 | Adjustable |
| C220 | 220 | 70 | 70 | 20 | Adjustable |
| C250 | 250 | 70 | 70 | 20 | Adjustable |
Punching is set to your drawing. “Adjustable” means hole diameter and spacing are made to order.
Mass, Ix, Wx and Iy for every thickness
| Model | Thickness mm | Mass kg/m | Ix cm⁴ | Wx cm³ | Iy cm⁴ |
|---|---|---|---|---|---|
| C80 | 2.0 | 2.98 | 38.57 | 9.64 | 10.07 |
| C80 | 2.5 | 3.73 | 47.60 | 11.90 | 12.65 |
| C80 | 3.0 | 4.47 | 56.39 | 14.10 | 15.26 |
| C100 | 2.0 | 3.77 | 76.51 | 15.30 | 20.06 |
| C100 | 2.5 | 4.71 | 94.66 | 18.93 | 25.17 |
| C100 | 3.0 | 5.65 | 112.42 | 22.48 | 30.32 |
| C120 | 2.0 | 4.08 | 117.12 | 19.52 | 21.42 |
| C120 | 2.5 | 5.10 | 145.20 | 24.20 | 26.89 |
| C120 | 3.0 | 6.12 | 172.80 | 28.80 | 32.40 |
| C140 | 2.0 | 4.40 | 168.14 | 24.02 | 22.58 |
| C140 | 2.5 | 5.50 | 208.74 | 29.82 | 28.36 |
| C140 | 3.0 | 6.59 | 248.78 | 35.54 | 34.19 |
| C160 | 2.0 | 5.02 | 255.32 | 31.91 | 35.67 |
| C160 | 2.5 | 6.28 | 317.29 | 39.66 | 44.77 |
| C160 | 3.0 | 7.54 | 378.54 | 47.32 | 53.96 |
| C180 | 2.0 | 5.34 | 336.25 | 37.36 | 37.05 |
| C180 | 2.5 | 6.67 | 418.21 | 46.47 | 46.52 |
| C180 | 3.0 | 8.01 | 499.34 | 55.48 | 56.07 |
| C200 | 2.0 | 5.65 | 430.78 | 43.08 | 38.27 |
| C200 | 2.5 | 7.07 | 536.12 | 53.61 | 48.06 |
| C200 | 3.0 | 8.48 | 640.54 | 64.05 | 57.95 |
| C220 | 2.0 | 6.28 | 587.24 | 53.39 | 56.21 |
| C220 | 2.5 | 7.85 | 731.18 | 66.47 | 70.56 |
| C220 | 3.0 | 9.42 | 873.97 | 79.45 | 85.04 |
| C250 | 2.0 | 6.75 | 793.37 | 63.47 | 58.35 |
| C250 | 2.5 | 8.44 | 988.43 | 79.07 | 73.27 |
| C250 | 3.0 | 10.13 | 1182.18 | 94.57 | 88.32 |
Computed from the nominal dimensions for Q235 strip. The same values drive the online span calculator and the downloadable span tables.
How to size one
Four steps. The online calculator does all of them for the whole range in one pass.
Open the span calculatorSteel grade, coating and thickness
- Grade. Q235 / S235 is standard for purlins; Q355 / S355 is available where the design calls for it.
- Coating. Z275 galvanised is the normal export specification. Heavier coatings are worth specifying for coastal or high-humidity sites.
- Thickness. 2.0, 2.5 and 3.0 mm are the standard gauges in the tables above. Other gauges are quoted on request.
- Standard. Cold-formed sections to GB 50018; tolerances and hole positions confirmed on the approved drawing before rolling.
Punching, sag rods and cleats
Holes are punched to your layout or to our standard pattern, whichever you prefer — the dimension tables above show where a fixed pattern exists. Sag rods, cleats, sleeves and angle brackets are cut and drilled to match the same drawing, so a pack arrives ready to bolt rather than ready to modify.
Documentation and quality
Every shipment ships with mill test certificates, a packing list and a certificate of origin. The plants work to ISO 9001, ISO 14001 and ISO 45001, and copies of the certificates are available on request. Third-party pre-shipment inspection can be arranged if your buyer requires it.
Packing, loading and order quantity
Purlins are bundled and steel-strapped, with each bundle marked to the packing list so site can match it to the erection drawing.
We build the loading plan before packing: lengths, bundle count and the container mix are worked out together, because purlin bundles are what usually decide whether a 40HQ closes properly.
Order quantity depends on the section, the gauge and how the mill run is set up. Send the schedule — lengths, sections and total tonnage — and we will confirm what can be rolled together in one run.
Get a price on C purlins
Send the section, gauge, lengths and total tonnage — or just the drawing. You get a priced offer with the packing and loading plan, normally within one working day.
C purlin questions we get asked
Z if the roof run is long enough for lapping to pay off, C for wall girts, eave members and short single spans. The full comparison is in our C versus Z guide.
It depends on span, purlin spacing and load, not on preference. A 6 m span at 1.5 m spacing under a normal roof load usually lands on 2.0 or 2.5 mm; longer spans push you to 3.0 mm or to a deeper section. Run the numbers in the span calculator.
Yes. Send the hole diameter, spacing and edge distances with the order, or attach the erection drawing and we will confirm the pattern back to you before rolling.
Yes — sag rods, cleats, sleeves and angle brackets are made to the same drawing, so the whole fixing package ships together.