Impacts of the social subcontract and last planner system interventions on the trade-crew workflows of multistory residential construction projects

Despite empirical evidence of the effects of the Last Planner System. (LPS), the mechanisms by which it works are less well understood. Its strengthening of the social networks within construction projects implies the possibility of enhancing collaboration using means other than or in addition to the LPS. Inspired by Rousseau's Social Contract, a new management artefact called the Social Subcontract (SSub) was devised to test this hypothesis. The impacts of SSub and LPS interventions on the workflow in eight residential construction projects were studied using action research over periods from 7 to 16 months. The results provide anecdotal evidence that application of SSub together with LPS improves coordination and workflow more than application of LPS alone. SSub also appears to motivate the general contractor to perform the make-ready process, which otherwise is often not implemented. The research provides new understanding of how the LPS functions. It contributes to industry and academia by relating theory to practice, potentially strengthening the confidence with which practitioners can apply such interventions to improve production flows.