Traditional Timber Roof With Purlins

This is a large timber running at right angles to the rafters and usually positioned mid span.

Traditional timber roof with purlins.

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. Of course if there is intermediate support you can get away with a lighter and cheaper truss. The purlins are supported by struts which in turn are supported on an internal load bearing wall. 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. Video of traditional cut roof detail. Purlins are 2 by 4 feet and are installed much like metal roofing. Under purlins were typically propped off internal walls.

The collar ties are used to connect the rafters preventing them from spreading outwards. 3 lean to roofs less common. There are two basic methods of pitched roof construction. Roofs and not for traditional purlin and rafter roof construction.

The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction. Purlin plate principal purlin and common purlin. 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. It is a very common form of construction.

It is a horizontal bar that used to support building at the roof structurally. Building control guidance note purlin and rafter. The collar ties and hangers are used to improve the overall strength and stability of the roof. 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.

A common arrangement is a rafter and purlin system which combines purlins and rafters. In traditional timber framing there are three basic types of purlin. For example an 8 x 4 under purlin would support the center of a row of 6 x 2 rafters that in turn would support 3 x 2 roof purlins to which the roof cladding was fixed. Roof trusses can also span much greater distances without intermediate support than traditional beams purlins and joists.

In lightweight timber roof construction under purlins were used to support rafters over longer spans than the rafters alone could span. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. Purlin is a well known material in the field of architecture structural building or structural engineering. All the figures are based on roofing tiles or slates laid on.

Is possible compared with about 5m.