C purlins are essential steel members in prefabricated and PEB structures. Many people ask how to join c purlins, how to install them, what connection details to follow, what span to expect, and how much they cost. This guide gives you clear answers.
You will learn:
- C purlin installation preparation: hole alignment, coating, and transport checks
- Step-by-step installation guide: orientation, spacing, and tool checklist
- C purlin connection details: overlap, sleeve, butt, miter, and bracket methods
- Common mistakes and solutions: misalignment, torque, bracing, and corrosion issues
- C purlin sizes, span chart, and price guide: from 100mm to 300mm with factory-direct wholesale supply
- Manufacturer support: certified Steel Structures / PEB Structures Manufacturer & Producer with technical guidance
Whether you are a builder, contractor, or buyer, this article helps you avoid mistakes and get factory-direct certified C purlins at wholesale prices from SteelPRO PEB.
C Purlin Installation Preparation: Hole Alignment, Coating, and Transport Checks
Before starting c purlin installation, you must prepare carefully. The key checks are hole alignment, coating compatibility, and transport deformation. These steps prevent costly rework and ensure a smooth project.
1. Hole Alignment Tolerance
- Even a 2mm misalignment in pre-drilled holes can delay the project.
- If you use non-matching connectors, holes may not align and cause a full rework.
- Always use factory-punched C purlins for perfect fit.
- If sourcing parts separately, check hole spacing with a calibrated steel ruler before installation.
2. Coating Compatibility
- Mixing the wrong sealants or fasteners can damage the galvanized coating.
- In coastal or humid areas, corrosion happens in 6 months if coatings mismatch.
- Use neutral-cure sealants and zinc-friendly fasteners only.
- A coating thickness gauge ensures the purlins have enough protection.
3. Transport-Induced Deformation
- Cold-formed steel may bend slightly during transport.
- Small bends (up to 3°) usually recover during installation.
- Let purlins rest for 24 hours after unloading.
- If still bent, use controlled clamping—never force into place.
- Forcing bent purlins into place will cause rebound and later misalignment.
Use SteelPRO PEB factory-direct C purlins with pre-punched holes, certified coatings, and protected delivery to avoid all these risks.
Step-by-Step C Purlin Installation Guide: Orientation, Spacing, and Tools
Correct c purlin installation ensures structural stability, prevents misalignment, and extends building lifespan. The key steps are checking materials and tools, fastening purlins, aligning orientation, and adding bracing. Follow this guide to install with confidence.
Material and Tools Check
Before installation, make sure all purlins and tools meet the requirements.
- Inspect purlins for bends, cracks, rust, or coating defects.
- Verify thickness with a caliper (e.g., 1.5mm or 2.0mm).
- Check hole alignment with the blueprint. A 1mm mismatch per joint can lead to 10cm misalignment over 10m span.
Tool Checklist:
| Tool | Purpose |
| Electric screwdriver | Secure screws and bolts |
| Torque wrench | Tighten to correct torque (28 Nm) |
| Laser level | Keep alignment precise |
| Scaffolding/Ladders | Ensure safe access |
Installation Steps
- Secure Purlins to Frames
- Use Tek screws for thin steel and bolts for heavy loads.
- Keep screws 20mm from the edge to prevent tearing.
- Place two fasteners per joint, spaced 50mm apart.
- Align Purlins Horizontally
- Install with opening facing up for cladding and drainage.
- After every 3 purlins, check alignment with a spirit level.
- If misaligned, loosen screws, adjust with a rubber mallet, and retighten.
- Add Bracing for Stability
- Install steel straps every 4–6m as temporary bracing.
- Never stack roof panels on unbraced purlins—this causes warping.
Span and Orientation
Proper orientation and spacing prevent structural failure.
C Purlin Span Chart:
| Purlin Size | Max Span (m) | Recommended Use |
| 100mm | 4.0–4.5 | Light roofs, small sheds |
| 150mm | 5.5–6.0 | Standard warehouse roofs |
| 200mm | 6.5–7.0 | Heavy-duty roof structures |
| 300mm | 8.0+ | Long-span or industrial use |
- Rule of thumb: 1.2m spacing for light roofs, 1.8m for heavy snow or load conditions.
- Always confirm with local building codes.
For certified factory-direct C purlins with precise punching and reliable span performance, contact SteelPRO PEB manufacturer for wholesale supply.
How to Join C Purlins: Connection Details and Best Methods
Many builders ask how to join c purlins together. The most common connection methods are overlap, sleeve, butt, miter, and bracket connections. Each method has its own use, strength, and limitations. This section explains each type with steps, best practices, and a comparison table.
Overlap Connection
- Best for long spans and heavy loads.
- Extend overlap to 600mm for high snow or wind zones.
- Fix with staggered Tek screws (No. 12 gauge) at 75mm intervals.
- Torque: 15–20 Nm.
Example: A warehouse with 500mm overlaps and 8 screws per joint resisted 80kg/m² snow load without deflection.
Sleeve Connection
- Best for aesthetic projects (office, retail).
- Sleeve length: 600mm total (300mm per side).
- Leave a 2mm thermal gap between purlins.
- Fix with M12 bolts, 4 per side.
Advantage: Creates seamless joints while allowing thermal expansion.
Butt Joint with Splice Plates
- Best for short spans (<4m) where overlap is not possible.
- Use 6mm-thick splice plates, 150mm beyond each end.
- Drill holes 50mm from plate edges.
- Use M12 bolts with lock nuts.
Limitation: Carries 25% less load than overlap—avoid in heavy loads.
Mitered Connections for Sloped Roofs
- Best for pitched roofs (up to 30°).
- Use CNC factory-cut purlins to avoid misalignment.
- Bolt with 4 M12 bolts; shim gaps >1mm with galvanized strips.
Angle Bracket Connections
- Best for high-stress junctions (e.g., beams supporting HVAC).
- Use L-shaped 5mm steel brackets, every 1.2m.
- Torque: 35 Nm (to beam), 25 Nm (to purlin).
Prevents twisting and long-term deflection.
| Method | Best Use | Strength | Limitation |
| Overlap | Long spans, heavy load | Very strong | Needs longer material |
| Sleeve | Aesthetic projects | Medium | Requires thermal gap |
| Butt Joint | Short spans <4m | Medium-low | 25% weaker than overlap |
| Mitered | Sloped roofs | Strong if CNC | Errors with manual cutting |
| Brackets | High-stress junctions | Reinforced | Extra material needed |
Less Common Connection Types
- Welded C Purlins: Permanent, high-strength connections requiring skilled execution. Best for heavy-duty loads, but not ideal in coastal areas without corrosion-resistant coatings.
- Bolted Connections for Flexibility: Modular and easy to disassemble, often used where structures require adjustments over time.
- Clamp Connections:A no-drill, quick-install solution for temporary structures like event tents.
- Interlocking Sleeve Connections: Provides hidden joints for architectural purlins, but is limited to axial loads only.
- Hybrid Approaches: Mixes different connection types for custom applications, such as using overlaps at mid-span and sleeves at the ends for a combination of strength and aesthetics.
What is the best way to join C purlins for long spans?
Overlap connections with 600mm extension and staggered screws provide the highest load capacity.
Can C purlins be welded instead of bolted?
Welding is possible but not recommended in coastal or humid areas because welds corrode faster. Bolted or sleeved joints are safer.
Choose factory-direct C purlins with pre-cut overlaps, sleeves, or splice kits from SteelPRO PEB to save time and ensure certified strength.
Common Mistakes When Installing or Joining C Purlins
Many failures in c purlin installation and joining come from simple mistakes. The most common are misalignment, wrong torque, no expansion gap, missing bracing, and using the wrong connection type. This section lists the errors, problems they cause, and the correct solutions.
| Mistake | Problem | Solution |
| Misaligned purlins | Causes cladding fit issues and weak joints | Use adjustable clamps and laser level; factory-punched purlins prevent mismatch |
| Under- or over-torqued screws | Loose joints (too low) or coating damage (too high) | Tighten to 15–20 Nm using torque wrench; mark screws with paint for check |
| No thermal expansion gap | Purlins buckle or crack with temperature change | Leave 1.5–2mm expansion gap at sleeves; use expansion bolts in hot regions |
| Misaligned bolt holes | Increases tear-out risk under load | Drill holes 50mm from plate edge; use 6mm splice plates extending 150mm |
| No angle brackets in high-stress zones | Twisting or deflection under heavy loads (e.g. HVAC) | Install 5mm steel brackets every 1.2m; torque 35 Nm (beam), 25 Nm (purlin) |
| Manual miter cutting | Creates 2–3° misalignment in sloped roofs | Use CNC pre-cut purlins; shim >1mm gaps with galvanized strips |
| Welding in humid/coastal areas | Welded joints corrode faster | Use bolted or sleeved joints with corrosion-resistant coatings |
| Wrong connection type | Weak joint or load failure | Use overlap for strength, sleeve for looks, butt joints only for <4m spans |
Bonus Tips:
- Even a 3mm misalignment can cause serious issues over long spans.
- Skipping temporary bracing may cause collapse under strong wind.
- Factory-direct C purlins reduce these risks by ensuring correct punching, coating, and joint kits.
Avoid costly rework. Order certified SteelPRO PEB C purlins with factory-prepared holes, coatings, and connectors for faster, error-free installation.
C Purlin Sizes, Span Chart, and Wholesale Price Guide
Many buyers search for c purlin sizes, span charts, and prices before ordering. This section gives you a quick reference to common sizes (100mm–300mm), their span capacity, and typical wholesale price ranges. All sizes are available factory-direct from SteelPRO PEB with certified quality.
C Purlin Sizes and Span Chart
Different sizes of c purlins carry different loads. Use the span chart below as a general guide:
| Purlin Size | Thickness Range | Max Span (m) | Typical Application |
| 100mm | 1.5–2.0mm | 4.0–4.5 | Light roofs, sheds, small canopies |
| 150mm | 1.8–2.5mm | 5.5–6.0 | Standard warehouse roofs |
| 200mm | 2.0–3.0mm | 6.5–7.0 | Medium to heavy-duty roofs |
| 300mm | 2.5–3.5mm | 8.0+ | Long-span or industrial projects |
Always confirm span with project-specific design loads and local building codes.
C Purlin Wholesale Price Reference
Prices vary by size, thickness, and coating. Below is a general FOB reference range (for bulk orders):
| Purlin Size | Approx. Price (USD/ton) | Notes |
| 100mm | $620–680 | Light duty, fast-moving stock |
| 150mm | $640–700 | Popular for warehouses |
| 200mm | $660–720 | Stronger for heavy roofs |
| 300mm | $680–750 | For industrial applications |
Bulk orders enjoy lower prices. Factory-direct supply ensures stable quality and certified coating (Z275 or higher).
Factory-Direct Supply of C Purlins，Steel Structures Manufacturer Support
Our Factory Advantages
- Factory-direct wholesale supply: Lower cost, consistent quality
- Certified production: Laser-cutting with ±1mm tolerance, Z275+ galvanized coating
- Custom kits: Pre-drilled holes, labeled components, ready-to-install packages
- On-site support: Installation coaching and technical consultation
Proven Project Results
- 60m warehouse: Double-fastened end brackets, zero uplift after 3 typhoons
- Coastal resorts: Hybrid stainless purlins (AZ150), 5+ years corrosion-free
- Industrial factory: Angle-bracket reinforced joints, prevented long-term deflection
Why Partner With SteelPRO PEB
- Reliable PEB Structures Manufacturer & Producer
- End-to-end support: From load calculation to final assembly
- Bulk supply with international certification
- Lifetime technical consultation
Contact SteelPRO PEB engineers today at [peb@SteelPROgroup.com] to get your factory-direct quotation for C purlins and complete steel structure solutions.
Related Reading: Joists and Rafters: What’s the Difference and Why It Matters
