What is difference between purlin and rafter?

What is difference between purlin and rafter?

Both rafters and purlins are beams. And they both occur mostly in roofs. The difference is that, if you stand facing the ridge of a roof, purlins span left to right, and rafters span down to up. Rafters can also be trussed rafters, so they might form a triangular shape and have triangulated sections within.

Can purlins be used as rafters?

Purlins traditionally support the roof deck / cladding / sheeting and are in turn supported by the principal rafters / steel beams etc. In some instances, either 6″ or 8″ “C” purlins back to back can be used as rafters. This is known as a lightweight steel system.

What are steel purlins used for?

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. Purlins are a key component to the secondary frame of commercial, residential and industrial metal buildings.

Why do you need purlins?

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.

Do roofs need purlins?

you only need perlins to support the rafters if they will not support the span needed. so a rafter of 150 x 50mm at 400 centers would be adequate.

How far can steel purlins span?

A four-inch purlin can span 12 feet. A six-inch purlin can span 18 feet. An eight-inch purlin can span 25 feet. A ten-inch purlin can span 30 feet.

What is the purpose of the purlin in a roof truss?

Purlin plates are beams which support the mid-span of rafters and are supported by posts. By supporting the rafters they allow longer spans than the rafters alone could span, thus allowing a wider building.

Does metal roof need purlins?

So, What Are Purlins? According to Elite Steel and Supply, metal roof purlins are an important part of achieving excellent metal roofing installations that last for decades with low maintenance and unlikely repairs.

What is the most common spacing for rafters?

Builders aren’t bound by standard rafter spacing measurements. But they do tend to space rafters in one of several industry-standard increments, typically either 12, 16 or 24 inches apart.

Does a metal roof need purlins?

In general, purlins are used instead of traditional decking when it comes to metal roofs. Decks can help support the enormous weight of roofing more easily, and therefore are recommended for larger projects, like industrial and commercial metal roofing.

What is a purlin in construction?

Definition of Purlin in Construction. A purlin is a small structural member that spans between larger structural members. In a metal structure, the purlins can be in the walls or ceilings, and are used to attach the exterior skin of the metal structure, the interior finishes, or support the wall and ceiling installation.

What is purlin bracing?

The rafters are the beams of wood angled upward from the ground. They meet at the top of the gable at a ridge beam, which has extra bracing to attach it to the rafters. The purlins are the large beams perpendicular to the rafters; from this shot, it appears that there are three purlins on either side of the roof.

What is a purlin roof?

In architecture or structural engineering or building, a purlin (or purline) is a horizontal structural member in a roof.