Rafter And Purlin Roof

A common arrangement is a rafter and purlin system which combines purlins and rafters.

Rafter and purlin roof.

Purlin and rafter roofs timber sizes and construction details keywords. The support system for the roof is comprised of ridgepole and rafters or purlins. Hip rafters are simply called hips and are shown here as brown. This type of roof is exactly right as it has a steep pitch and lots of clear space between the timber framework.

In architecture or structural engineering or building a purlin or purline is a horizontal structural member in a roof. 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. Hip roofs have hip rafters which are oriented diagonally to the ridge and outside walls. Besides providing support for the roof rafters and purlins add to the interior beauty so you often see log purlins and rafters that match the wall logs.

Rafter and purlin style roofs are usually found in properties built before the mid 1960s and they are absolutely ideal for those property owners who are looking to convert their loft. Stabilization typically involves installation of a purlin system. Using a combination of rafters and purlins is common. With rafters it runs in perpendicular from the walls to the ridge while with purlins it runs to the ridge in parallel.

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. 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. A rafter and purlin roof and shows the dimensions referred to in the tables above. The main difference between rafter and purlin is that the rafter is a structural members in architecture and purlin is a structural member in a roof.

If you see sagging rafters recommend stabilization by a qualified contractor.