Gross density of wood (Part 2)

As the mass of wood depends of the water content in wood, the value "gross density" depends on the humidity of the wood. In literature the value of gross density is indicated for the humidity of wood for the indoor usage or dry wood.

PN = gross density in indoor climate (about 12 % humidity)

PO = gross density with 0% humidity (dry wood)

The following schedule shows differences in gross density for some types of timber in dry state. These differences in density are based on the following facts: origin of a tree, location und environmental condition the tree is exposed to during growth. The differences of the gross density within one type of wood depend on the different width of the annual tree ring. In the Scandinavian countries, where the vegetation periods are much shorter, for example the annual tree rings of usual spruce grow are narrower than in the middle of Europe where the vegetation periods are much longer and the climate more moderate. This is the same reason why spruce in high mountains has narrower annual tree rings than in lowland. Good (warm and humid) or bad (cold and dry) years reflect in wide or narrow annual tree rings. That’ s the reason why literature does only show an average or margins for the gross density for one type of wood.

Specification about gross density for different types of timber in dry content (from…. till)

Quelle: Gesamtverband Deutscher Holzhandel / German Timber Trade Federation