Roofing timber design

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.

How to use graphs

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:

Roof Concrete tiles 38 & 50mm

Roof Concrete tiles 76mm

Roof Concrete tiles Laminated 32 & 45mm

Roof Concrete tiles Laminated 70 & 100mm

For metal sheeting (IBR, Chromadek etc) use the following tables:

Roof Metal Sheeting 38 & 50mm

Roof Metal Sheeting 76mm

Roof Metal Sheeting Laminated 32 & 45mm

Roof Metal Sheeting Laminated 70 & 100mm


Manufacturing a truss on site ?

The following tables give basic top chord and bottom chord sizes.

Basic truss design tables:

Trusses Concrete tiles

Trusses Metal Sheeting