In unstable environments, characterized by frequent client-driven changes in design criteria and by huge pressure to compress project delivery times, practitioners must search for innovative ways to structure the design-build process. Involving specialty contractors from project inception onwards, helps to satisfy client needs. Based on empirical research in the semiconductor industry, this paper presents a product-process model that reflects the joint system of designing and building a facility component. The model expresses, in a parametric fashion, critical design, procurement, and construction decisions as the design-build process unfolds. A model implementation that uses discrete-event simulation contrasts the effects of early vs. late specialty-contractor involvement in design. Results show that early contractor involvement benefits the average project duration but increases the duration variability and may significantly increase the waste of construction resources if improperly implemented. Postponement of design decisions helps to reduce waste without penalizing the project duration much. Results also show that fabrication decisions should not be neglected in early design efforts when expediting a project.
design-build development process, design postponement, specialty contractor knowledge, design criteria change, discrete-event simulation, early commitment, postponement