Purlin

The Oxford Dictionary suggests a French origin, with the earliest quote using a variation of purlin in 1447, though the accuracy of this claim has been disputed.

Purlin plates are very commonly found in large old barns in North America.

"[2] Common purlins in wood construction, also called a "major-rafter minor-purlin system".

Common purlin roofs in North America are found in areas settled by the English and may have been a new invention in the Massachusetts Bay Colony.

Historically, these roofs are found in New England, the highest concentration in Maine, and isolated parts of New York and along the St. Lawrence River in Canada.

Purlins are most commonly used in Steel Framed Building Systems, where Z-shapes are utilized in a manner that allows flexural continuity between spans.

Note: The sketches in this section reference terminology commonly used in the UK and Australia.

A view of a roof using common purlin framing. The purlins are marked in red. This view is from the inside of the building, below the roof. 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. The sheathing boards are sometimes called the roof deck and are painted white.