Purlin is a well known material in the field of architecture structural building or structural engineering.
Traditional timber roof with purlins.
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.
They give added support to the roof and also provide a nailing surface for the end panels and drip edge.
Purlin plate principal purlin and common purlin.
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.
Is possible compared with about 5m.
In traditional construction spans of over 3 metres or so were often dealt with by adding a purlin.
In lightweight timber roof construction under purlins were used to support rafters over longer spans than the rafters alone could span.
A common arrangement is a rafter and purlin system which combines purlins and rafters.
Purlins are 2 by 4 feet and are installed much like metal roofing.
It is a very common form of 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.
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.
The collar ties and hangers are used to improve the overall strength and stability of the roof.
This is a large timber running at right angles to the rafters and usually positioned mid span.
They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top.
It is a horizontal bar that used to support building at the roof structurally.
Roof trusses can also span much greater distances without intermediate support than traditional beams purlins and joists.
Purlins are installed horizontally under metal roofs.
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 collar ties are used to connect the rafters preventing them from spreading outwards.
In traditional timber framing there are three basic types of purlin.
There is an available purlin for every type of roofing material including purlin span for metal roof which is the most common material type to use this item.
Video of traditional cut roof detail.
All the figures are based on roofing tiles or slates laid on.
3 lean to roofs less common.
A truss roof using factory made trusses which are delivered to site complete and just erected.
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.
Under purlins were typically propped off internal walls.
