The design of a constructed facility involves all the large and small decisions required to determine its form, how its elements work individually and in combination to fulfil their functional requirements, what materials will be used in construction, how these are connected together, how the facility is to be constructed, and how it should be maintained and operated. It is the design that determines not only the form and nature of the construction, but also the economic characteristics of the constructed facility such as its durability, the ongoing operating and maintenance costs and ultimately its commercial life.

This paper discusses a number of aspects of structural design to explain the difference between design life and service life, an issue that may be important in the context of design and construct contracts. The “default” legal obligation to prepare a design with due skill and care is contrasted with the common contractual obligation for a constructed facility to be fit for purpose. These issues are illustrated by reference to recent case law.