5. Grading structural wood

In fact, the properties of wood from trees are highly variable. This variability, which may disconcert engineers accustomed to artificial, homogeneous and isotropic materials, is the result of the history of the structural timber.

It depends on genetics, silviculture and environment (climate, soil, altitude, etc.).

It is the result of structural factors linked to the wood's anatomy (sapwood, heartwood, initial wood, final wood, etc.).

Lastly, it depends on the history of any treatments applied to the material (drying, moisture absorption, etc.).

This variability not only exists from one species to another (interspecific variability), but also within the same species (intraspecific variability) and within the same tree.

In the absence of classification, variations...