Planning for uncertainty: use of structural equation modelling to determine the causal structure of time buffer allocation

Construction personnel at every level of management are constantly planning and trying to figure out how to best deal with the uncertainty and variability of construction projects. The allocation of a time buffer in task planning is one method used to absorb variation caused by the inherent complexity and uncertainty present in construction. The research objective is to identify the causal structure used in planning for uncertainty and allocating a time buffer to construction project tasks. A time buffer questionnaire was developed and distributed to 175 companies across 37 states in the US. A structural equation modelling approach was used to develop mental models for field management personnel and upper management personnel based on both the frequency and severity response data collected. A total of 63 completed surveys from construction field managers were collected to validate the models. Contributions to the body of knowledge include (1) the development of causal structures for decision support through identification of risk areas, and the prioritization, prevention, and mitigation of those risks; and (2) the comparison of the field management models with the upper management models to identify both the shared key causes of buffer allocation and the differences in planning priorities. The contribution to practice is that the findings will help construction managers understand what drives the need for buffers in their construction schedules and allow them to focus efforts on strategically addressing the most critical areas of concern and uncertainty. Furthermore, the execution of a model survey serves to strengthen the findings of the data analysis and improve the overall models from a practical standpoint.