Timber Roof Purlins

Purlins are 2 by 4 feet and are installed much like metal roofing.

Timber roof purlins. Purlin is a well known material in the field of architecture structural building or structural engineering. In lightweight timber roof construction under purlins were used to support rafters over longer spans than the rafters alone could span. Purlins are non pressure treated 1 x 4 x 12 lumber that is installed on to the roof in a specific layout pattern and screw pattern. It is a horizontal bar that used to support building at the roof structurally.

There is an available purlin for every type of roofing material including purlin span for metal roof which is the most common material type to use this item. They meet at the top of the gable at a ridge beam which has extra bracing to attach it to the rafters. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. The purlins are the large beams perpendicular to the rafters.

The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to. They give added support to the roof and also provide a nailing surface for the end panels and drip edge. From this shot it appears that there are three purlins on either side of the roof. The rafters are the beams of wood angled upward from the ground.

Do all roofing projects require purlins. Under purlins were typically propped off internal walls.