Float types in construction spatial scheduling

Earlier studies investigated spatial scheduling to link schedules of construction activities to workspace availability and constraints. However, previous models lacked the ability to quantify criticality in a manner similar to the critical path method. Previous spatial scheduling models did not provide seamless integration with site logistics planning of material staging and temporary facilities. This paper therefore extracts various float types that can exist in a spatial schedule. Three activity float metrics are defined using singularity functions: shift, rate, and combined floats. An algorithm is established to generate space float contours for a construction site. A validation example demonstrates the new float concepts and space float contours. This research makes two contributions to body of knowledge of construction scheduling. First, activity float metrics expand the capabilities of spatial scheduling models to assess the criticality of activities. Second, the concept of space float enables a direct integration between scheduling and other project management tasks like site layout, material logistics, and trades coordination.