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Are you planning to build a new shed or cabin? Are you unsure about which material would be best for you? 

Flat steel sheets when rolled into specific shape and thickness that range between 1mm to 3mm is called Purlins. In the construction industry, purlins are used to build roofs and support the deck. Purlins are also known as rolled-form or cold-form steel. High-quality tensile galvanized steel is used to make purlins.

Why should galvanized steel matter to you?

Galvanized steel is a result of steel dipped in a liquid Zinc coating that keeps the material from rusting. This makes the purlins more durable, safe in the worst of rains, and easier maintenance.

Based on the shape, purlins are of two types- C and Z Purlins. The C purlins are in the shape of a ‘C’, whereas the Z shape of purlins is in the shape of a ‘Z’.

Generally, C purlins are used to make the main portal frames of a purlin shed. Purlins are best suited for sheds that are less than 12 meters. But some manufacturers sell designs up to 24-meter in span. But the increased length decreases the strength, making it less resistant to nasty weather.

Purlins provide additional support for the roof: They create a horizontal “diaphragm” that supports the weight of your building’s roof deck – whatever material you use for the roof itself. They also help make your entire roof structure more rigid.

A metal purlin is a lightweight, horizontal beam or bar that is used for structural support in roofing. In addition to providing support, metal purlins also increase a building’s resistance to heavy winds.

Purlin is a horizontal beam or bar used for structural support in structures, most often below the roof. Purlins are supported either by the building’s rafters or its walls. These are most commonly used in metal buildings, but in wood-frame structures, these also replace closely packed rafters.

What is Purlin in PEB?

Purlins are steel elements that are used as support structures in pre-engineered buildings, mainly below the roofs. Purlins provide extra roof support, creating a horizontal diaphragm that provides support to the weight of the roof and deck. Purlins are installed parallel to the building eave and are supported by rafters or walls. The raw material used to fabricate purlins is cold-formed steel. It can span a length of up to 30 feet or longer. The length and width depending on the dimensions of the primary frame of the building, its usage, and engineering design. Added stiffness can be given to purlins to prevent loss of structural strength, as required. Purlins are therefore an important part of the roof structure.

C and Z Purlins are the steel structures used in the secondary framing of pre-engineered buildings. These provide support to the roof and also transfer the load to the primary structure. The purlins are in turn supported by roofs or walls.

In pre-engineered buildings, steel purlins are widely used. They are lightweight, durable structures that are built to precision, having consistency in dimensions.

Comparison In Between CR Steel Purlin & HR Steel Purlin 

CR Steel Purlin ( Cold Rolled Steel )

HR Steel Purlin  ( Hot Rolled Steel )

Very high strength-to-weight ratio

Low strength-to-weight ratio

Sections provided with painted galvanized coated surface finish depending on customer’s requirements

Available without any surface finish

Sections are maintenance-free owing to the application of proper surface finish

Sections require frequent maintenance

Light sections reduce dead load and consequently and its supports lighter sections for structures and supports. Thus, the load on the foundation is minimum

Self-weight requires heavier sections for the structures thereby increasing the load on the foundation

Sections are factory-finished to avoid wastage

High wastage since sections are available only in standard lengths and shapes

Factory-finish sections drastically & pre punching facility available in the factory to reduce installation time

Installation time is high since sections need to be cut to length and fabricated & punching at the site

Optimum sections to meet exacting design specifications: as per cut to length available as customer requirement no over-design possible.

Only standard sections are available

An additional factor of safety is due to increase in yield strength by cold forming

Factor of safety as per specifications

We really hope this gives you a clear picture of C and Z purlins and how you can use them smartly. Like with every other thing, the purlins have its limitation. But it is important to notice which one outweighs the other.



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