For timber, the classical meaning of density as the “mass of a substance per unit volume”, requires some clarification, as the term is used in different ways depending on the trade and the context. As timber is also a hygroscopic material, any density value is affected by the moisture content at the time of measurement.
Timber density is not only relevant for determining self-weight. It is often used to characterise wood quality in forestry, it is used to determine fastener strength when designing structures, and it is also used to describe the charring rate of timber members in fires. This technical note summarises the various definitions of density used both in forestry and timber engineering and relates these to the commonly used timber design standards used in New Zealand, Australia and Europe.
