Modular construction is popular, yet architects and engineers often lack knowledge about manufacturing, supply, and assembly, hindering implementation. To help to address this issue, the study proposes using “configurators” to customize building layouts based on design requirements, building system constraints, and available options. These configurators use computational design processes to optimize, evaluate and frame aspects throughout early construction stages. The study conducted a literature review to identify domains involved in the configuration system for each stage of an Off-Site Construction project and tested configurators available in the market against criteria for modular construction projects. Finally, the study proposes a customized BIM-based configuration system to address the found limitations, that could be enriched with different databases to evaluate design options. The research focuses on applying configurators for modular construction systems for medium-density residential buildings to address Canada’s housing crisis.