A reasonable-skill-and-care obligation requires competent professional performance, while an express fitness or performance obligation may require the promised result. The contract must be construed before deciding which obligation applies

A professional designer, such as an architect or consulting engineer, ordinarily owes only reasonable skill and care: the design is not negligent merely because it fails, and the designer is judged by the competent professional of the day, with a state-of-the-art defence. A design-and-build contractor may assume an express or implied obligation to achieve a result fit for a disclosed purpose. Whether that obligation exists, and its extent, depend on the contractual words and the circumstances in which any term is implied. In MT Hojgaard, the Supreme Court construed the twenty-year design-life requirement and the J101 obligation together. Compliance with J101 did not answer the separate design-life requirement on those contractual documents. The standard forms often reduce a contractor's fitness duty to reasonable skill and care, in part because fitness for purpose is hard to insure.