跳到内容 Steel C purlins, also known as steel C channels, are crucial structural components widely used in roofing, wall framing, and other construction applications. Their distinctive “C” shape provides excellent strength, durability, and ease of installation, making them ideal for supporting building structures, especially in industrial and commercial buildings.
This article focuses on steel c channel sizes, providing a detailed overview of C purlin span tables, size selection criteria, and installation methods. The goal is to help B2B buyers, engineers, and contractors make informed decisions when selecting steel C channels for their projects. Our company, StrutcChannel.com, offers a wide range of steel C channels tailored to various structural needs.
What Are Steel C Purlins?
Steel C purlins are horizontal structural members with a cross-section shaped like the letter “C.” They support roof and wall cladding by spanning between rafters or columns. Typically made from cold-rolled or hot-rolled steel, C purlins come in various sizes and thicknesses and are often coated to resist corrosion.
Importance of the C Purlin Span Table
The C purlin span table is a critical tool that guides the selection of appropriate purlin sizes based on span length, load conditions, and spacing. It ensures structural safety, cost efficiency, and compliance with building codes.
Types of C Purlin Span Systems
- Single Span System: One purlin spans the entire length between supports.
- Double Purlin Span System: Two purlins share the span, supported at the center and ends.
- Double Lapped System: Two purlins overlap slightly in the middle for extra support.
- Continuous Lapped System: Multiple purlins are spaced and overlapped continuously for long spans.
Benefits of Using Steel C Purlins
- No need for drilling or cutting on-site.
- Strong and reliable with a high strength-to-weight ratio.
- Lightweight, reducing transportation and installation costs.
- Easy to install with standard tools.
- More economical than traditional structural steel beams.
Steel C Channel Sizes and Span Capacities
C purlins are available in various sizes, commonly identified by their depth (height of the “C”), flange width, and thickness. Typical sizes include 100 mm, 150 mm, 200 mm, 250 mm, and 300 mm depths.
Typical Span Capacities by Size
| Purlin Size (Depth) | Typical Maximum Span (Single Span, meters) | Typical Maximum Span (Double Span, meters) |
|---|---|---|
| 100 mm | 2.5 – 3.5 | 3.5 – 4.5 |
| 150 mm | 3.5 – 4.5 | 4.5 – 5.5 |
| 200 mm | 4.5 – 5.5 | 5.5 – 6.5 |
| 250 mm | 5.5 – 6.5 | 6.5 – 7.5 |
| 300 mm | 6.5 – 7.5 | 7.5 – 8.5 |
Note: Actual span capacity depends on load conditions, purlin thickness, and spacing.
C Purlin Span Table for 150 mm C Purlins
| Section | Wind Category | Spacing (mm) | Max Allowable Span (mm) | No. of Bridging Rows |
|---|---|---|---|---|
| C150-12 | TC1 | 900 | 5700 | 0 |
| 1200 | 6100 | 1 | ||
| 1500 | 6600 | 2 | ||
| C150-15 | TC2 | 900 | 7000 | 0 |
| 1200 | 7400 | 1 | ||
| 1500 | 7900 | 2 | ||
| C150-19 | TC3 & 4 | 900 | 8200 | 0 |
| 1200 | 8200 | 1 | ||
| 1500 | 9100 | 2 |
Table 1: Maximum Allowable Span for 150 mm C Purlins by Wind Category and Spacing
Factors Affecting C Purlin Span Selection
- Load Type: Dead loads (roofing materials, insulation) and live loads (snow, wind, maintenance).
- Purlin Spacing: Typical spacing ranges from 900 mm to 1500 mm.
- Wind Category: Higher wind loads reduce allowable span.
- Bridging: Installation of bridging increases span capacity and stability.
- Purlin Thickness: Thicker purlins support longer spans.
How to Determine the Right Size Metal Purlins for Your Project
Selecting the ideal metal purlin size for your metal building comes down to matching structural requirements with practical considerations. Here’s how you can simplify the process:
1. Identify Your Required Span and Load
- Begin by determining the distance your purlins need to span between supports and the expected loads—both live (like snow and maintenance workers) and dead (weight of roofing materials).
- Refer to manufacturer-provided span tables (such as the ones above) to narrow down suitable depths and thicknesses for your specific spans.
2. Understand Purlin Sizing Codes
- Metal purlins are usually identified by their depth (web height), flange width, section type, and material thickness.
- For example, a “C150-15” designates a C purlin with a 150 mm depth and a nominal thickness of 1.5 mm. These numbers help ensure the purlin you select matches architectural and structural plans.
3. Consider Section Type and Thickness
- Section types include C (channel), Z (with a “zig-zag” profile suitable for lapping), and other variations.
- Thickness is typically measured in millimeters or as “gauge/mil,” impacting both capacity and weight.
- Common C purlin thicknesses range from roughly 1.2 mm to 3.0 mm depending on structural demand.
4. Reference Industry Standards and Tables
- Use recognized span tables based on standards from organizations such as the Steel Stud Manufacturers Association (SSMA) or similar bodies in your region. These tables incorporate essential factors like wind category, spacing, and required number of bridging rows to help you select the right size for safe and efficient construction.
5. Confirm with Project Specifications
- Always cross-check your selection with the project’s architectural drawings and load calculations.
- When in doubt, consult with a structural engineer or your steel supplier for guidance. Over-specifying may unnecessarily increase cost, while under-specifying could compromise safety.
By following these steps, you’ll be able to confidently choose the correct purlin size, ensuring both safety and value in your metal building project.
Difference Between C Purlins and Z Purlins
While C purlins and Z purlins may look similar at first glance, their profiles and structural applications set them apart.
- C Purlins feature a straightforward, “C”-shaped cross-section with parallel flanges. This makes them ideal for use as horizontal supports in roofs and walls, and they can also serve as floor joists. C purlins are easy to install and are often chosen for simple spans between rafters or columns where support is required without overlap.
- Z Purlins, on the other hand, are shaped like the letter “Z.” This distinctive profile allows Z purlins to nest together and overlap at joints. As a result, Z purlins provide enhanced strength and continuity across longer spans, making them the preferred choice for larger roofing projects or when multiple purlins must be lapped for added stability.
In summary, C purlins are best suited for straightforward applications with shorter spans, while Z purlins excel in situations requiring longer spans or continuous structural support through overlapping.
Galvanized vs. Red Oxide Purlins: What’s the Difference?
When choosing steel C purlins for your project, one of the first decisions you’ll face is the type of protective coating. The two most common finishes you’ll encounter are galvanized and red oxide. While both serve to protect the steel and enhance its longevity, they differ in several key ways:
- Galvanized Purlins:
These purlins are coated with a layer of zinc through a hot-dip galvanizing process. The zinc coating provides robust corrosion resistance, making galvanized purlins ideal for outdoor use or humid environments where moisture protection is a priority. Think warehouses, factory roofing, or agricultural buildings exposed to the elements. - Red Oxide Purlins:
Red oxide purlins, on the other hand, are treated with a red oxide primer—a paint-like coating applied to bare steel. This primer helps prevent rust during fabrication, shipping, and short-term storage. Red oxide purlins are often chosen for projects where purlins will be sheltered from direct weather or where additional painting and finishing will be done after installation (such as in interior structures).
In summary:
- Use galvanized purlins when long-term corrosion resistance is needed, especially for exterior applications.
- Choose red oxide purlins for cost-effective interior framing or when further painting and finishing are expected on site.
Selecting the right finish ensures your steel C channels stand the test of time—regardless of where they’re installed.
Additional Resources for Learning About Metal Roofing and Purlins
If you’re interested in deepening your knowledge of metal roofing systems and the crucial role of purlins, there are several top-notch educational resources available online:
- Video Tutorials: Platforms like YouTube host a wide range of installation demonstrations and walkthroughs from industry experts. Look for channels from building material suppliers such as BlueScope Steel and Tata Steel, which often share best practices and helpful tips.
- Technical Blogs: Reputable sources like the Metal Construction Association (MCA) and the American Iron and Steel Institute (AISI) regularly publish guides and articles covering span tables, proper installation, and recent advances in purlin technology.
- Interactive Span Calculators: Many steel manufacturers, including StruM.I.S and Simpson Strong-Tie, provide free online tools to help you select the right steel C channel for your specific load requirements.
- FAQs and Whitepapers: Standards organizations like ASTM International frequently release technical documents, case studies, and answers to common questions about steel structure design and safety criteria.
- Design Guides: Books such as “Design of Cold-Formed Steel Structures” by ECCS are excellent references for those seeking in-depth engineering insights.
Whether you prefer watching, reading, or using interactive tools, these resources make it easier to understand the key factors influencing metal roof and purlin selection—empowering contractors, engineers, and DIY enthusiasts alike to make more informed decisions.
Installation Guidelines
- Install purlins perpendicular to rafters or beams.
- Maintain consistent spacing as per design.
- Use bridging when spans exceed recommended lengths.
- Secure purlins with appropriate fasteners.
- Avoid cutting or drilling purlins on-site to maintain structural integrity.
Advantages of Using Span Tables
- Ensures safety and compliance with engineering standards.
- Optimizes material usage, reducing costs.
- Simplifies design and construction planning.
- Provides clear guidance for installers and engineers.
Summary Table: C Purlin Sizes and Span Capacities
| Size (mm) | Thickness (mm) | Typical Spacing (mm) | Max Span (m) | Typical Applications |
|---|---|---|---|---|
| 100 | 1.5 – 2.0 | 900 – 1500 | 2.5 – 3.5 | Small sheds, verandahs |
| 150 | 2.0 – 2.5 | 900 – 1500 | 3.5 – 4.5 | Garages, industrial buildings |
| 200 | 2.5 – 3.0 | 900 – 1500 | 4.5 – 5.5 | Medium warehouses, workshops |
| 250 | 3.0 – 3.5 | 900 – 1500 | 5.5 – 6.5 | Large commercial buildings |
| 300 | 3.5 – 4.0 | 900 – 1500 | 6.5 – 7.5 | Heavy industrial structures |
Conclusion
Selecting the correct steel c channel sizes based on span tables is essential for structural safety, cost efficiency, and durability. Understanding the span capabilities of different purlin sizes, considering load conditions, spacing, and wind categories ensures optimal performance.
At StrutcChannel.com, we provide a comprehensive range of steel C channels, backed by expert guidance and customization options to meet your project’s specific requirements.
