Implications of Even Flow Production Methodology for U.S. Housing Industry

Production building in the residential sector is often described as the portion of the construction industry that is most like the manufacturing sector. In modern tract construction in the United States, a small number of models are generally repeated several times in a relatively confined area, using specialized trade contractors to complete each phase of each home. Management of the handoffs between predecessor and successor trade contractors is therefore a critical component in the successful completion of a residential project. In order to bring more reliable planning to this process, a workflow-leveling strategy known as even flow production has come into use in the industry in recent years. Even flow production is a strategy intended to reduce the variability in the workflow for trade contractors in the process, thereby gaining production efficiencies. In practice, different operational definitions are in use. This paper describes a series of simulation experiments to identify the management implications of two common strategies (activity-based versus start-based). A special-purpose simulation template was built for the Simphony environment for this purpose. The pace chosen for the flow of activities was found to significantly affect the speed at which the subdivision was completed. The even flow strategy was found to affect the subdivision completion time only slightly, but to have a significant impact on workflow variability and management effort. Control of the pace of starts of only the first activity exhibited nearly the same degree of variability as if the pace of starts were matched to a sales pace.