One of the fundamental requirements under the Construction Products Directive (CPD) stipulates that “a structure shall be designed and executed in such a way that it will sustain all actions and influences likely to occur during executions and use and that it will meet the specified serviceability requirements during its intended life”.

The concept of design life of a structure is explained with reference to EN 1990. Load situations expected during the design life of a structure is looked at and various types of loadings are described. The importance of duration of loading in terms of timber design is explained and the five different load duration classes defined in Eurocode are summarised.