Steel Purlins: 10 Things You Need to Know Before Buying

If you speak to someone in the construction industry, they will more than likely know what a steel purlin is. However, if you bring this up with someone outside the industry, you might only get a blank stare. That is because not everyone knows this term.

There are plenty of entities that have metal purlins for sale, and you might reach out to one if you need some for your next construction job. First, though, let’s go through a quick crash course on steel purlins for anyone who doesn’t know very much about them yet.

What is a Steel Purlin?

Let’s start with the basics. A purlin is a horizontal bar that is generally made of steel, though you can sometimes find them made of other metals or composite materials.

You will most often see them in buildings that are composed entirely or mostly of metal. They are meant to support the weight of the roof and whatever other materials are covering it.

Walls or Rafters Typically Support Them

Purlins are usually supported by walls or rafters. They run perpendicular to them. They form a crucial part of the secondary framing system.

It’s important to have them there. If you have a building composed primarily or mainly of steel, the weight of it can be an issue if you don’t have the secondary framework in place of which the purlins are a part. That’s why, if you look at the construction of any modern roof, you should immediately notice the purlins if you know what one looks like and the way they are usually situated.

The Steel is Shaped Using a Cold Form Process

Purlins are also usually made from a metalworking process commonly called cold forming. If you shape pieces of metal this way, what you are doing is working with them at or slightly above room temperature.

This allows you to bend the metal into the shape you want without heating or superheating it. This makes the process safer, since you’re not dealing with metal at higher temperatures, but it also means the strength and hardness of the finished product is a focal point. You usually need tools called dies and punches to press or strike the metal during the cold forming.

They Give You a Nailing Surface

If you add purlins to a roof, as happens so often in the construction of large buildings, part of what you are allowing to happen is the addition of pieces of structural support that give you a handy nailing surface. You can attach end panels of the roofing and the drip edge to the purlins.

When you do so, you get better overall structural strength. This is an aspect of engineering that has been around for decades, and no system or setup has been produced that’s superior to it.

You Can Add Finishes to Your Purlins

If you’re getting ready to buy some purlins that will be a part of a new building’s roof support system, you should also know that you can add finishes to them that will be beneficial in the long run. For instance, you might add galvanization, meaning you’re spraying on zinc for corrosion resistance.

That’s potentially useful, but spraying the purlins with red oxide is equally popular. This is where you coat them with a red layer of oxidized material that adds rust protection. It won’t keep the purlins from rusting forever, but you can usually get many years of use out of it.

There Are Better and Lesser Known Purlin Companies

If you’re getting ready to buy some purlins, you should also know that there are some companies that make them that are better known in construction circles, and others that are less so. This is true with virtually anything you can buy. In construction, though, the difference can be crucial.

Buying from a company that is known to make superior purlins might add a bit to the project’s total cost, but you’re getting enhanced stability. Most construction companies will agree that it’s worth it.

You Need to Install Them Correctly

When you buy your purlins, you need to install them correctly. Welding or hot cutting them is generally not considered to be advisable.

That is because you will damage the protective coating. You will also want to think about the impact you’re making on the steel’s properties when you’re using these installation techniques. If you’re losing stability and strength, which will almost certainly be the case, a roof caving in could be the eventual result.

You Must Consider the Purlin’s Relationship with Other Roof Elements

No less important is considering the purlin’s relationship with the other roof elements to which it will be attached or that will be positioned close by. Purlins are meant to work in conjunction with rafters. This forms the roof’s framework.

They also work with sheeting. This is common roofing material. If you don’t have the purlins configured in such a way that they work in conjunction with the sheeting and rafters, you risk the roof collapsing.

You Can Learn More About Purlins if You Get an Engineering Degree

You can learn a lot more about purlins if you get into engineering at the collegiate level. There are also several other areas of higher learning where you will be required to learn about them.

It’s by no means impossible to learn how to use purlins if you don’t have a degree in one of these disciplines. However, it’s at least worth considering getting this kind of education before you get into a profession where you will be using this kind of building material a lot.

You Can Often Save Cash By Buying in Bulk

One final thing you should know about purlins is that the more of them you buy, the more likely a company is to give you a discount. Much like virtually any other kind of construction material, the more of it you need, the more likely a supplier will be to give you a price reduction.