Model of trade-off between overlapping and rework of design activities

An effective and well-known technique for earlier completion of construction projects is to overlap the project activities that normally would be performed in sequence. Overlapping, often called fast-tracking, is inherently risky because it increases uncertainties and can result in more changes and rework. In order to gain maximum advantages from early project completion, a trade-off between benefits and losses of activity overlapping is required. In this paper, a new model has been developed to (1) explain in detail the mechanism and characteristics of design activity overlapping and (2) formulate and discuss design activity overlapping time-cost trade-off. A qualitative research methodology including interviews and focus groups with experts was used to generate and refine the model. This model contributes to the body of knowledge of construction management by demonstrating (1) how to analyze multipath networks through introducing the multi-predecessor effect and (2) how to analyze concurrent overlapping through introducing the cascade effect. The results of this paper can generate insights for further research to solve the overlapping time-cost trade-off and determine the optimum overlapping degree.