Roof trusses consist of a network of members, joined in a way which can hold the roofing structure for longer spans, without the need of columns. Roof trusses are common in buildings of Steel with roof sheets. Steel trusses prove economical for span greater than 12 meter.
Rectangular Tubes, Angles of Steel can be used as members for trusses. Depending on the requirements, there are many types of trusses. Selection of truss also depends on the slope of the roofing. Minimum recommended slope is 1/6 for steel sheets. Spacing between the trusses is generally kept around 1/4 of the span, for span upto 15m and 1/5 of the span, for span between 15m-30m.
For an economical design, cost of trusses should be equal to twice the cost of purlins plus the cost of roof coverings.
Cost of Trusses = 2 x (Cost of Purlins) + (Cost of Roof Coverings)
Simple Google Images search for “Roof Trusses”, shows the types of trusses and basic examples for the same.
One of the primary advantage of a truss is that it uses less material to support a given load, when compared to a beam.