Empirical determination of the smallest batch sizes for daily planning

Level of development (LOD) 400 is the level of building information modeling (BIM) defined for fabrication and, hence, the level appropriate for defining the daily scope of construction work. However, when a supervisor needs to define which LOD400 objects to build on a specific day, they are faced with the problem of high granularity (number of objects, occlusions, and small size of objects), which complicates the selection of objects. To address this problem, this research explored the idea of forming a small batch that represents a building block of a construction task, which can be used to group a set of LOD400 objects and reduce the granularity a supervisor needs to interact with. Because this batch size may differ between trades, field observations were done on 56 construction tasks for 24 trades at 5 sites. Based on an analysis of these observations, the main contributions of the paper are the identification of nine types of smallest batch sizes and the definition of the concept of a smallest workface boundary (SWFB). The batch sizes form volumetric boundaries that group a set of LOD400 objects. This volumetric boundary, referred to as a SWFB, reduces the granularity a supervisor has to interact with when using LOD400 objects for defining daily scopes of work. Applications of the nine types of smallest batch sizes in the form of SWFBs to sample LOD400 models showed that the granularity a supervisor has to interact with was reduced by 94.0% and 99.5% for the number of objects and occlusions, respectively, and small objects (<200 mm) were eliminated.