Timber Roof Purlins

It is a horizontal bar that used to support building at the roof structurally.

Timber roof purlins.

From this shot it appears that there are three purlins on either side of the roof. 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. 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.

Under purlins were typically propped off internal walls. In lightweight timber roof construction under purlins were used to support rafters over longer spans than the rafters alone could span. Purlin is a well known material in the field of architecture structural building or structural engineering. This is a very traditional concept in heavy timber roof framing.

They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to. Purlins are 2 by 4 feet and are installed much like metal roofing. They give added support to the roof and also provide a nailing surface for the end panels and drip edge.

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. Do all roofing projects require purlins.