Purlins, widely used in construction, support the roof deck of steel buildings, extending their lifespan. They are essential in pre-engineered steel structures, passing through rafter beams. If you wish to learn about the main types of Purlins, then this blog is for you.
What is a Purlin?
Purlins are horizontal beams that give structural support for buildings, usually located under the roof. They are supported by the structure’s walls or rafters and can be used in place of the closely spaced rafters in wooden buildings. Roof purlins are meant to hold the weight of the roof deck, which is built of weatherproofed and insulated materials such as panels or sheet metal.
Types of Purlins
Currently, manufacturers produce two different types of purlins:
- C Shaped Purlins
- Z Shaped Purlins
C Shaped Purlins
C purlins, as the name indicates, are formed in the same way as the C letter and are generally used for wall and floor support. C-section purlins, also known as cee-section purlins, are manufactured to form the walls and floor joists of a building shell construction, making them appropriate for supporting the flooring beams.
Advantages of C Purlins
- Durable.
- No need for drilling on the sides.
- Can cover long distances easily.
- Assured straightness.
- No need for cutting.
Z Shaped Purlin
Z purlins are a stronger alternative to C purlins. They are often employed in joint and overlap areas of buildings. They are used as horizontal beams to shape the roof and wall joists, provide support for roofing sheets, and ensure a solid connection.
Z purlins are commonly used in industrial and agricultural structures due to their flexibility and lightweight qualities, making them adaptable to a broad range of sizes and uses.
Advantages of Z Purlins
- Z purlins can be placed on top of each other.
- Very strong.
- Saves a lot of material by making the purlins shorter in height.
What Purpose Do Purlins Serve in a Steel Building?
To understand the purpose of purlins, let’s start with the fundamentals of roof purlins in metal construction.
Purlins are an essential component of a pre-engineered steel structure. They run perpendicular to the rafters and support the roof. They have three primary functions: they protect the roof, reinforce the frame by connecting the rafters, and give additional support between framing parts. Purlins also help to increase the structure’s resistance to excessive rainfall.
Spacing for Purlins
Metal purlin spacing is important for a strong and reliable roofing system. The weight of the structure should normally determine the distance between purlins and rafters, which is normally 12-24”. However, this varies.
Building rules and manufacturers often suggest spacing purlins 30” apart for steel framing and 38” for carrying sheathing.
In Conclusion
Understanding the different types of purlins available is important for making the right choice for your construction project. If you have any questions about the type of purlin you should use for your project or need pricing estimates, please call Fort Bend Steel Supply at (281) 499-5800.