Traditional Purlin Roof Construction

There are three types of purlins in wood construction.

Traditional purlin roof construction.

Every member of a traditional cut roof is individually cut and assembled on site. There are two basic methods of pitched roof construction. 3 lean to roofs less common. In architecture or structural engineering or building a purlin or purline is a horizontal structural member in a roof.

Purlin in architecture structural engineering or building a purlin or historically purline purloyne purling perling is any longitudinal horizontal structural member in a roof except a type of framing with what is called a crown plate. In traditional construction spans of over 3 metres or so were often dealt with by adding a 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. This is a large timber running at right angles to the rafters and usually positioned mid span.

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. Traditional roofs work by distributing loads from the rafters down through to the wall plate and then through to the walls below. Once the purlins are in place the panels can be craned in in a matter of minutes. The longitudinal horizontal beam that is sitting on a post or the principal rafter of a truss and used to support common rafters.

Purlin plate principal purlin and common purlin. A common arrangement is a rafter and purlin system which combines purlins and rafters. Nails bolts and screws create a mechanical fixing to stop uplift through wind etc. 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.

The beams will typically be placed along the ridge at the eaves and halfway between the two where they are known as purlins. Sips panels these panels are from sipco need to be craned into place. It is a very common form of construction. 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.

Purlin plates under purlin principal purlins and common purlins. In traditional timber framing there are three basic types of purlin. The rafters are the main load bearing elements of the roof. They span from the wallplate to the ridge board providing a platform for the underlay battens and tiles.

The best way to transfer load is with a timber to timber joint a compression fixing. Exposed rafters are a feature of some traditional roof styles. 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.