Roofing timber design
It is vital that the correct structural timber is used for your roof.
Please note that the following graphs are provided as information only and we accept no liability for the use of these graphs.
We recommend that a structural engineer assists in the design of timber structures.
Consult with your roof sheeting supplier to determine the correct purlin spacing. A number of factors determine roof construction design: Weight of ceiling, beams, insulation, windows. Wind loading. Roof pitch etc.
For concrete tiles and fibre cement roof sheeting use the following tables:
For metal sheeting (IBR, Chromadek etc) use the following tables:
Manufacturing a truss on site ?
The following tables give basic top chord and bottom chord sizes.
Basic truss design tables: