For many reasons, subcontracting is prevalent throughout the construction industry. Multiple subcontractors each perform work on multiple projects simultaneously. Each subcontractor strives to win sufficient jobs so as to ensure a ready supply of available work; each project manager strives to control the subcontractors on his/her project to maintain cost- and schedule-compliance, often pushing them to perform even when conditions preclude efficient or quality work. Construction subcontracting suffers the ills of traditional push workflows, but the problem for individual projects is exacerbated by subcontractors optimizing their workload across multiple projects, creating a snowball effect of growing instability for each individual project. Much of the research and implementation of lean construction has been carried out within the conceptual boundary of a single project or a single value stream. This paper proposes a multi-project, multi-subcontractor approach aimed at developing better understanding of workflow from the subcontractors' point of view, and contributing to development of a multi-project and multi-sub-contracting theory of production in construction projects. It attempts to define the questions, scope and methods for the research. A solution approach using an economic model is proposed. The long-term goal is to enable development of sub-contracting relationships and management procedures that harness the potential for both contractors and sub-contractors to benefit.
Subcontracting, multiple projects, theory, resource allocation, lean construction.