Structural timber span tables

Structural timber span tables

It is vital that the correct structural timber is used for your structure.

Please note that the following graphs are provided as information only.
We accept no liability for the use of these graphs.
We recommend that a structural engineer assists in the design of timber structures.

Somerset Timbers Joist span table for decking and flooring – summary for S5 Pine and Garde 8 Laminated beams.

How to use graphs


Detailed graphs for flooring: 

SA Pine 22mm flooring must be supported every 450mm.

Floor joists 38 & 50mm

Floor joists 76mm

Floor joists Laminated 32 & 45mm

Floor joists Laminated 70 & 100mm


Detailed graphs for roofing:

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.

Roof Concrete tiles 38 & 50mm

Roof Concrete tiles 76mm

Roof Concrete tiles Laminated 32 & 45mm

Roof Concrete tiles Laminated 70 & 100mm

Roof Metal Sheeting 38 & 50mm

Roof Metal Sheeting 76mm

Roof Metal Sheeting Laminated 32 & 45mm

Roof Metal Sheeting Laminated 70 & 100mm


Basic truss design tables:

Trusses Concrete tiles

Trusses Metal Sheeting