Using the last planner system and lean principles to improve workflow in BIM-based building design projects

Several studies have found that traditional design planning to be unreliable and a cause of workflow variability during design development. The reason given for this is that traditional design planning lacks a mechanism to control workflow. Other studies have shown that the Last Planner system (LPS) of production planning and control reduces workflow variability during the construction stage of building projects by increasing planning reliability through greater collaboration in the planning of construction tasks and better coordination of work between the building trades. It is believed that LPS can also reduce workflow variability during the design stage by increasing planning reliability through greater collaboration in the planning of design tasks and better coordination of work between the design disciplines. In recent years, there has been a move toward collaborative and coordinated working practices in design firms, which has necessitated the formation of architectural/engineering (AE) firms, where all the design disciplines are involved in developing a design, aided by Building Information Modeling (BIM) tools. It is believed that, as processes that promote collaboration and coordination, LPS and BIM can be combined to improve design workflow beyond the degree to which it might be improved by the application of either of these innovations independently. It has also been suggested that there are synergies between Lean and BIM that can be exploited during design development to remove waste, reduce workflow variability and thus improve design workflow. These theories need further testing. Using action research (AR) and working closely with thirty-three design practitioners, the researcher facilitated the implementation of LPS weekly work planning (LPS WWP) and the realization of lean principles through BIM during the design development phase of a seven-story hotel and a six-story apartment at two different AE firms in Florida. Implementation of LPS WWP focused on increasing planning reliability to reduce workflow variability. The realization of lean principles focused on reducing waste in the BIM process through greater collaboration and better coordination between the various design disciplines. A Lean/BIM interaction matrix developed by Sacks et al. (2009) was used as a framework for exploring positive interactions between twenty-four lean principles and seven BIM functionalities. Percent Plan Complete (PPC) measurements taken before and after the implementation of LPS WWP suggest that LPS WWP was effective in improving workflow in both design projects: PPC increased by an average of 12.1% in the hotel project and by an average of 13.9% in the apartment project after LPS weekly work planning was implemented, representing an upward trend in PPC and continual improvement in design workflow. Eight lean principles were realized through the seven BIM functionalities used in both design projects, resulting in thirty-three discernible positive interactions in the hotel project and twenty-nine discernible positive interactions in the apartment project and contributing to the overall improvement in design workflow. This research has demonstrated that LPS WWP can reduce design workflow variability by increasing design planning reliability and that lean principles can be realized through greater collaboration and better coordination between the various design disciplines during the BIM process to reduce waste and improve design workflow during design development. It recommends that future implementation of LPS in design projects should consider LPS at the WWP level only and during the design development phase only. It also recommends that BIM should be used during design development as a design tool and not just as a visualization tool so its lean potential can be fully exploited. Further research is suggested for identifying and addressing causes of variability in design workflow other than poor design planning.