Commercial timber species number in the hundreds. A very smaller number are commonly specified and used. Like all plants, timber species are divided into different groups according to their defining botanical features, which are found in their leaves, fruit, bark and wood structure, and which may be seen with the naked eye. It is these botanical and biological features and the chemical characteristics of the wood species that determine how we specify and use different timbers.
The botanical and biological features of the wood species are taken into account when specifying timber for structural use.
Commercial timber species are divided into two groups, ‘Hardwoods’ and ‘Softwoods’.
A timber’s strength class is determined by its strength grade and species.
Moisture content is an important influence in the density of timber, which in turn is often a good guide to its properties.