Design requirements for roof trusses
The design of a timber roof truss must accord with engineering principles and with AS 1720.1. This includes the wind design. AS 4440-1997 'Installation of nail plated timber roof trusses' provides details for correct practices when installing roof trusses.
Trusses are usually spaced at regular intervals, typically 600 mm, 900 mm or 1,200 mm apart. The spacing depends on the mass of the roofing material and local practice. A range of truss types can be configured to attain different shapes.