Module: Construction principles Unit: Principles of design with timber

Date Published

15 August 2022

Document Type



Timber is, in many respects, the ideal construction material. It is strong in both tension and compression, has a high strength-to-weight ratio, it is light (compared with most alternative materials), can be easily worked and is easy to handle. Overall it presents few problems during construction.

In most design circumstances it is common for the design life to be specified as 50 years. However, a properly designed and maintained timber building can last for centuries.

For less permanent structures a 10-year design life may be assumed and it may also be considered that some elements of a structure have a shorter design life and will be replaced as part of the maintenance management.

Key Information

The structural properties of timber are highly variable, dependent upon density, moisture content, temperature, grain deviation and knots.

The moisture content of timber varies with relative temperature and humidity. This variation results in radial and tangential movements, but it is relatively stable along the grain.

Changes in temperature can cause short-term differential movement in timber. The coefficient of thermal expansion of timber along the grain is smaller than that of steel or concrete and it has lower thermal expansion characteristics than those of masonry and steel.

Case studies

When the nuclear power plant at Chernobyl exploded in 1986, it devastated the land and people of Belarus with radioactive fallout, contaminating a quarter of the country. A new timber chapel commemorates the thirtieth anniversary of that terrible event, which forced thousands of people to evacuate their homes and land and settle elsewhere.

Wintringham Primary Academy is a three-form entry primary school that uses cross laminated timber to create an inspiring learning environment, built to impressive sustainability standards.