The cost-benefit of slack in production planning and control in construction projects

Production planning and control (PP&C) in construction projects addresses a wide diversity of variabilities that must be matched by a corresponding wide diversity of controls. These diverse controls might be accounted for by the concept of slack practices and resources (SPR), an extension of the buffer concept. Decision-making on the allocation of SPR often occurs under time pressure and without monetary data, demanding a suitable analytical approach. This paper introduces a method for assessing the cost-benefit of SPR in PP&C in construction. The method includes a questionnaire designed to be answered by practitioners involved in the creation of SPR. It enables the assessment of the net benefit value of each SPR, which - along with other data (e.g. monetary costs, if available) and consideration of contextual factors - supports decision-making regarding resource allocation. The application of the method in a construction project revealed 15 SPR, 11 of which should be maintained as they were. This suggests that the unstructured decision-making by employees was often effective, though not always. The findings also led to five propositions that guide the method's application, emphasizing the cost-benefit of opportunistic SPR, the different perspectives on SPR allocation, and the value of human-based slack.