Traditional Purlin Roof Construction

The best way to transfer load is with a timber to timber joint a compression fixing.

Traditional purlin roof construction.

3 lean to roofs less common. The use of purlins as opposed to closely spaced rafters is common in pre engineered metal building systems and both the ancient post and beam and newer pole building timber frame construction methodologies. Nails bolts and screws create a mechanical fixing to stop uplift through wind etc. Traditional roofs work by distributing loads from the rafters down through to the wall plate and then through to the walls below.

In traditional construction spans of over 3 metres or so were often dealt with by adding a purlin. This is a large timber running at right angles to the rafters and usually positioned mid span. There are two basic methods of pitched roof construction. Sizes used in traditional roofing construction.

All the figures are based on roofing tiles or slates laid on. Roofs and not for traditional purlin and rafter roof construction. In architecture or structural engineering or building a purlin or purline is a horizontal structural member in a roof. Common purlins in wood construction also called a major rafter minor purlin system.

Building control guidance note purlin and rafter roofs timber sizes and construction details. Common purlins are typically trenched through the top sides backs of principal rafters and carry vertical roof sheathing the key to identifying this type of roof system. A truss roof using factory made trusses which are delivered to site complete and just erected.