Correlation between Size and Productivity for Modular Buildings

Abstract Construction productivity has remained stagnant for decades, prompting interest in modular construction as a more standardized and efficient method of delivery. However, little is known about how productivity differs across modular building categories or how it scales with project size. This study analyzed 491 modular projects (303 permanent and 188 relocatable) to examine these relationships across major sectors, including multifamily housing, dormitories, workforce housing, education, healthcare, office, retail, and special applications. Productivity was defined as gross square meters completed per day, and was assessed using descriptive statistics, Kendall’s tau- b correlations, and simple linear regression. The results show that permanent modular projects are more common and substantially larger than relocatable projects, and education is the most frequent category. Productivity varies widely across sectors, and categories characterized by standardized, repetitive layouts, such as workforce and multifamily housing, consistently achieve the highest productivity levels. Kendall’s tau- b analysis revealed significant positive correlations between project size and productivity in most categories, confirming that larger projects tend to operate more efficiently. Exceptions occur for permanent hotels and relocatable healthcare and retail, for which productivity does not increase meaningfully with size. Regression models reinforced these findings, showing that project size explains a considerable share of productivity variation, although the strength of this relationship differs by category. Overall, the study provides clear, category-specific evidence that economies of scale and learning effects are strongest in modular sectors with higher levels of standardization. These insights offer practical benchmarks for forecasting productivity, selecting suitable project types, and guiding strategic decisions in modular construction.