What Structural Timber Do I Need?

The structural timber you need depends on what the timber is supporting, the span involved and the construction of the project.

There is no single timber size that suits every structural job. Work from the project drawings, structural specification or other relevant design information before ordering.

Advice by Andrew Tsaroulla, Director of TSAR Building Supplies

Last updated: 10th October 2026

Start With the Timber Grade

Structural timber is strength graded.

TSAR supplies C24 carcassing timber for a range of building applications.

If a drawing or specification states C24, the grade should not be changed without checking the project requirements.

Check the Timber Dimensions

Structural timber is available in different:

Widths
Depths
Lengths
Grades

For example, a 47 x 100mm section is not equivalent to a deeper 47 x 200mm section.

The dimensions required depend on the job.

Nominal Size and Finished Size

Timber can be described using nominal dimensions, while the finished dimensions may be smaller after processing.

When checking your materials list, confirm whether the measurements refer to nominal or finished sizes. This matters where timber needs to fit particular connections or match an existing structure.

Send us the dimensions exactly as shown on your specification and ask us to confirm the supplied size before ordering.