Purlin Roof Support

Purlin plates are beams which support the mid span of rafters and are supported by posts.

Purlin roof support.

A purlin plate in wood construction is also called an arcade plate in european english under purlin and principal purlin. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. 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. By supporting the rafters they allow longer spans than the rafters alone.

The purlins of a roof support the weight of the roof deck. When made of wood it is usually covered with some sort of weatherproofing and sometimes an insulation material. 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. They give added support to the roof and also provide a nailing surface for the end panels and drip edge.

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. E purlin is an engineered lvl roof underpurlin to support stick roofs for tile and metal sheet cladding. Purlin plates in wooden construction. The term plate means a major horizontal supporting timber.

A common arrangement is a rafter and purlin system which combines purlins and rafters. Metal roof purlins are installed horizontally under metal roofs.