Traditional Purlin Roof Construction

Every member of a traditional cut roof is individually cut and assembled on site.

Traditional purlin roof construction.

The rafters are the main load bearing elements of the roof. Sips panels these panels are from sipco need to be craned into place. A cut roof this is the traditional method of cutting the timber on site and building up the roof using rafters ridge boards joists and purlins etc the exact details being determined by the size of roof size of timbers etc. Once the purlins are in place the panels can be craned in in a matter of minutes.

A common arrangement is a rafter and purlin system which combines purlins and rafters. There are three types of purlins in wood construction. Parts of a traditional queen post roof truss. Purlin plates under purlin principal purlins and common purlins.

The beams will typically be placed along the ridge at the eaves and halfway between the two where they are known as purlins. The roof support system is a ridgepole and either rafters which run perpendicular from the top of the walls to the ridge or purlins which run parallel to the ridge. In traditional construction spans of over 3 metres or so were often dealt with by adding a purlin. A truss roof using factory made trusses which are delivered to site complete and just erected.

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. Exposed rafters are a feature of some traditional roof styles. There are two basic methods of pitched roof construction. Purlin plate principal purlin and common purlin.

Purlins support the loads from the roof deck or sheathing and are supported by the principal rafters and or the building walls steel beams etc. In architecture structural engineering or building a purlin is any longitudinal horizontal structural member in a roof except a type of framing with what is called a crown plate. The best way to transfer load is with a timber to timber joint a compression fixing. It is a very common form of construction.

In architecture or structural engineering or building a purlin or purline is a horizontal structural member in a roof. Nails bolts and screws create a mechanical fixing to stop uplift through wind etc. 3 lean to roofs less common. The longitudinal horizontal beam that is sitting on a post or the principal rafter of a truss and used to support common rafters.

In traditional timber framing there are three basic types of purlin. They span from the wallplate to the ridge board providing a platform for the underlay battens and tiles. The overall construction of a traditional cut roof is to ensure that the load of the roof is evenly transmitted to the walls below.