What Is Purlin in Roof?

Roof purlins are horizontal roof beams that run perpendicular to the roof trusses or rafters and are used to support the rafters or roofing materials. Purlins are transverse bending (usually two-way bending) members that are typically designed as single-span simply supported Purlins. Purlins that are commonly used are solid web type and light steel truss type.

There are different types of roof purlins:

1. Channel steel purlin

Ordinary channel steel purlins and light channel steel purlins are the two types of channel steel purlins. Because the thickness of ordinary channel steel purlins is greater, the strength cannot be fully exerted, and the amount of steel used is relatively large. Although the light channel steel purlin outperforms the standard channel steel purlin, it is still not ideal.

2. Angle steel purlin

Angle steel purlins and ordinary angle steel purlins are easy-to-obtain materials, but their rigidity is poor and the amount of steel used is relatively large, limiting their use to situations with small spans, purlin distances, and loads.

3. Combined channel steel purlin

Two-angle steels are used to weld the combined channel steel purlin. The amount of steel used is less than that of standard channel steel, but the welding workload is greater, and it is suitable for spans of up to 4m.

4. Combined Z-shaped steel purlin

Similar to the combined channel steel purlin, the combined Z-shaped steel purlin is welded by two-angle steels. It is more reasonable than the channel steel section when the roof slope is 1/3.

5. Hot-rolled thin-walled H-shaped steel and high-frequency welded thin-walled H-shaped steel purlins

Hot-rolled thin-walled H-shaped steel and high-frequency welded thin-walled H-shaped steel (collectively "thin-walled H-shaped steel") are a new type of light-weight steel with thin webs, good bending stiffness, and relatively close moments of inertia in the directions of the two major axes. The flange plate is straight and simple to install.