Issues related to the formulation of the theory of construction are considered. The roles of a theory in science and in practice are discussed. It is argued that many theoretical problems related to construction are due to general deficiencies of engineering and production theories, caused by one of their conceptual foundations, the conversion model. The origin and evolution of the conversion model are discussed. The shortcomings of the conversion model are illustrated by the case of project management. The beginning of a transition from the conversion model to alternative models is observed in a number of engineering and production disciplines. A similar paradigm shift is needed also for construction.