Timber Roof Purlins

The purlins are the large beams perpendicular to the rafters.

Timber roof purlins.

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. 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. 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.

They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. They meet at the top of the gable at a ridge beam which has extra bracing to attach it to the rafters. From this shot it appears that there are three purlins on either side of the roof. Purlins are a series of horizontal timbers laid across or connected to as depicted above the principal rafters and support the roof covering typically 2 6 tongue and groove boards conventional or structural insulated panels sips and roofing.

It is a horizontal bar that used to support building at the roof structurally. The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to. Purlins are installed horizontally under metal roofs. This is a very traditional concept in heavy timber roof framing.

Purlins are 2 by 4 feet and are installed much like metal roofing. Purlin is a well known material in the field of architecture structural building or structural engineering.