What Are the Most Common Purlin Profiles? Types, Sizes & Uses
Purlins are one of the most important structural components in steel buildings, and they are almost always manufactured using roll forming. The most common purlin profiles are designed to provide strength, load support, and efficient installation in roofing and wall systems.
The main types used worldwide are C purlins, Z purlins, Sigma profiles, and hat channels, with variations depending on region and application.
C Purlins (Most Common and Versatile)
C purlins are the most widely used profile globally.
Key characteristics:
- “C” shaped cross-section
- Straight web with equal flanges
- Easy to manufacture and install
Typical sizes:
- Web height: 100 mm to 300 mm
- Thickness: 1.5 mm to 3.0 mm (can be heavier)
Applications:
- Roof purlins
- Wall girts
- Secondary structural framing
C purlins are popular because they are simple, cost-effective, and suitable for a wide range of building types.
Z Purlins (Best for Overlapping Systems)
Z purlins are very common in larger steel buildings.
Key characteristics:
- “Z” shaped profile
- Asymmetrical flanges
- Designed for overlapping installation
Typical sizes:
- Web height: 120 mm to 350 mm
- Thickness: 1.5 mm to 3.5 mm
Applications:
- Large-span roofs
- Industrial buildings
- Warehouses
The main advantage of Z purlins is that they can overlap at joints, creating stronger and more continuous structural systems.
Sigma Profiles (Heavy-Duty Structural Use)
Sigma profiles are used in heavier structural applications.
Key characteristics:
- Complex “Σ” shape
- High strength-to-weight ratio
- Designed for longer spans and higher loads
Typical sizes:
- Larger and thicker than C/Z profiles
- Used in heavy-duty structures
Applications:
- Large industrial buildings
- Infrastructure projects
- High-load roofing systems
Sigma profiles are less common than C and Z but offer higher performance.
Hat Channels / Top Hat Purlins
Hat channels are smaller, lighter profiles.
Key characteristics:
- “Hat” or “top hat” shape
- Lightweight
- Easy to install
Typical sizes:
- Smaller web and flange dimensions
- Thin material (often 0.8 mm to 2.0 mm)
Applications:
- Light framing
- Cladding support
- Ceiling systems
These are not used for heavy structural loads but are widely used in secondary applications.
Lipped vs Unlipped Purlins
Most modern purlins include lips (small return edges on the flanges).
Lipped purlins:
- Increased strength
- Better resistance to bending
- More commonly used
Unlipped purlins:
- Simpler design
- Lower cost
- Used in lighter applications
Regional Variations
Different regions use slightly different standards and naming:
- Africa → IBR-compatible purlins, C/Z profiles
- USA → Cee and Zee purlins (often heavier gauge)
- Europe → Cold-formed sections with stricter standards
- Asia → Wide range of C/Z profiles for industrial buildings
Which Purlin Profile Is Most Common?
Globally:
- C purlins → most common overall
- Z purlins → most common in large industrial buildings
Most steel building systems use a combination of both.
Why These Profiles Are Popular
These purlin types dominate because they offer:
- High strength with low material usage
- Easy roll forming production
- Standardized sizes
- Compatibility with roofing systems
They are also easy to transport and install, which is important for construction efficiency.
Frequently asked questions
What is the most common purlin type?
C purlins are the most widely used globally.
What is the difference between C and Z purlins?
C purlins are symmetrical, while Z purlins can overlap for stronger systems.
Are purlins always roll formed?
Most modern purlins are cold roll formed for efficiency and consistency.
Which purlin is strongest?
Sigma profiles and overlapping Z purlins provide the highest strength.
Can one machine produce both C and Z purlins?
Yes, many modern roll forming machines can produce both with adjustments.
Summary
The most common purlin profiles are:
- C purlins (most widely used)
- Z purlins (best for overlapping systems)
- Sigma profiles (heavy-duty applications)
- Hat channels (light framing and support)
These profiles are essential in steel construction and represent one of the most important and profitable product categories in roll forming.