Module: Structural characteristics Unit: Choosing timber species

Date Published

27 August 2022

Document Type




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.

Key Information

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.

Case studies

A new workshop/shelter for project work at the Architectural Association’s Hooke Park campus has been built and designed by the students themselves. The workshop is the latest in the collection of innovative timber buildings at Hooke Park.

The Great Barn at Harmondsworth is the largest timber-framed medieval building in the country and one of the few surviving:
a magnificent and remarkably preserved Grade I-listed building which is nearly a thousand years old.