Purlins
A metal building is only as strong as the framework holding it together. When roof panels, wall girts, and cladding systems need reliable secondary structural support, the purlin is the component that carries the load. Without properly sized purlins, panels sag between primary frames, fasteners lose holding power, and the entire building envelope is compromised.
Triple-S Steel® stocks a full range of steel purlins in both C and Z configurations, manufactured from 14-gauge steel in Red Primed and Galvanized finishes. Whether you are framing a warehouse roof, supporting wall cladding on a commercial facility, or building out an agricultural structure, our metal purlins provide the load-bearing capacity and dimensional consistency your project requires. We carry standard stock lengths and offer custom sizing for projects that demand exact specifications.
C Purlin (Cee Purlin)
The cee purlin is one of the most widely used secondary framing members in metal building construction. Its C-shaped cross section creates a rigid channel that resists bending under roof and wall loads while providing a flat, consistent surface for fastening PBR panels, Max-Rib panels, and other cladding systems.
Triple-S Steel® stocks C purlins in 14-gauge steel with a Red Primed finish. Galvanized C purlins are available by special order for projects that require additional corrosion protection in high-moisture or coastal environments.
Our C purlins are stocked in 25 FT lengths and available in seven sizes to accommodate a wide range of span and load requirements:
|
Item # |
Size |
A |
B |
Finish |
|
PN3 |
3" x 1 1/2" |
3" |
1 1/2" |
Red Primed |
|
PN42 |
4" x 2" |
4" |
2" |
Red Primed |
|
PN4 |
4" x 1 1/2" |
4" |
1 1/2" |
Red Primed |
|
PN6 |
6" x 2" |
6" |
2" |
Red Primed |
|
PN8 |
8" x 2 1/2" |
8" |
2 1/2" |
Red Primed |
|
PN8312 |
8" x 3 1/2" |
8" |
3 1/2" |
Red Primed |
|
PN10 |
10" x 2 3/4" |
10" |
2 3/4" |
Red Primed |
The "A" dimension refers to the web depth (the vertical face of the purlin), while the "B" dimension refers to the flange width. Selecting the right combination depends on your span distance, design load, and the spacing of primary frames. For projects where stock sizes do not align with your engineering requirements, contact our team about custom dimensions.
Z Purlin (Zee Purlin)
The zee purlin features an angled, Z-shaped profile that allows sections to nest and overlap at splice points along continuous spans. This overlap capability makes the Z purlin the preferred choice for multi-bay buildings where purlins must carry loads across two or more frame bays without interruption.
Where the C purlin works best in single-span applications, the Z purlin delivers superior performance in continuous-span framing by distributing loads more efficiently across lap connections. This results in fewer total purlins needed per bay and reduced material costs on larger structures.
Triple-S Steel® stocks Z purlins in 14-gauge steel with a Red Primed finish. Galvanized Z purlins are available by special order. Our Z purlins come stocked in 21 FT, 27 FT, and 30 FT lengths and are available in four sizes:
|
Item # |
Size |
A |
B |
Finish |
|
PN4ZEE |
4" x 2" or 2 1/2" |
4" |
2" or 2 1/2" |
Red Primed |
|
PN6ZEE |
6" x 2" or 2 1/2" |
6" |
2" or 2 1/2" |
Red Primed |
|
PN8ZEE |
8" x 2" or 2 3/4" |
8" |
2" or 2 3/4" |
Red Primed |
|
PN10ZEE |
10" x 2" or 2 3/4" |
10" |
2" or 2 3/4" |
Red Primed |
Z purlins offer variable flange widths (the "B" dimension) to accommodate different lap configurations and attachment requirements. Your building designer or engineer will specify the appropriate flange width based on the overlap needed at each splice point.
Roofing Purlins: How They Work in a Metal Building
Roofing purlins span horizontally between the primary rigid frames (rafters or trusses) of a metal building, creating the secondary structure that directly supports roof panels. They transfer wind uplift, dead loads from the panels themselves, and live loads such as snow and rain down into the primary frames and ultimately into the foundation.
In a typical metal building, purlins are spaced at regular intervals along the length of the roof, usually between 4 FT and 6 FT on center, depending on panel gauge, profile type, and local design loads. The purlin size, gauge, and spacing all contribute to the load capacity of the roofing system.
Triple-S Steel® also carries purlin caps for 4", 6", and 8" purlins, which provide a finished closure at the open end of C purlins at the eave line of a building.
Related Components and Accessories
Purlins are one part of a complete metal building components system. Triple-S Steel® stocks the full range of framing and finish components that work alongside purlins to complete your building envelope:
- Base Angle: Available in 14-gauge, Red Primed and Galvanized finishes. Stocked in 4" x 2" (20 FT and 25 FT lengths) and 2" x 2" (20 FT lengths). Base angle secures the bottom of wall panels to the concrete slab or foundation.
- Steel Open-Face Channel: Available in 14-gauge steel, Red Primed or Galvanized, in four sizes ranging from 4 3/16" to 10 3/16". Stocked in 25 FT lengths. An open-face channel serves as a receiver channel or framing support for door and window openings.
- Carport Rakes: Available for 4", 6", and 8" purlins. Carport rakes provide a finished edge at the open sides of carport and canopy structures framed with C purlins.
For panel, trim, gutter, and fastener options that pair with our purlin inventory, explore our full metal building components catalog or request a quote for a complete materials list.
Get Purlins for Your Next Project
Triple-S Steel® has been supplying steel to builders, fabricators, and contractors since 1960. Our metal building components inventory is stocked at locations across Texas and Tennessee, which means shorter lead times and lower freight costs for your project. Most components are made to order with lead times of just 2 to 3 days.
When stock lengths and standard sizes do not fit your design, our team can work with you on custom purlin solutions that match your engineering specifications. For large-scale or repeat orders, we offer competitive volume pricing.
Call us at 1(800) 231-1034 or request a quote to get pricing on C purlins, Z purlins, and the full range of components for your next project.
Frequently Asked Questions
A C purlin has a channel-shaped cross section with both flanges pointing in the same direction. A Z purlin has flanges that point in opposite directions, forming a Z-shaped profile. The Z shape allows adjacent sections to overlap at splice points, making Z purlins ideal for continuous multi-span framing. C purlins are typically used in single-span applications or where a simple channel profile is needed for wall girts and framing.
C purlins are stocked in 25 FT lengths, and Z purlins are stocked in 21 FT, 27 FT, and 30 FT lengths. The standard finish is Red Primed, which provides a protective base coat for field painting or interior use. Galvanized purlins are available by special order for projects that need enhanced corrosion resistance. If your project requires a length outside of our standard stock, contact our sales team to discuss custom options.
Yes. The same C purlin and Z purlin sections used for roof framing also serve as wall girts. When installed horizontally between columns on the sidewalls and endwalls of a metal building, purlins function as girts that support wall panels and transfer lateral wind loads into the primary frame.
Our Commitment To You
For more than 60 years, we've stayed committed to fair trade and long-term thinking, providing great products and unwavering service. Our team's flexibility and entrepreneurial spirit ensure tailored solutions that create opportunities for your success within our Triple-S Steel® family.