According to production process theory, customization is directly related to cost and inversely related to volume, efficiency, and productivity. However, customers generally desire products that are individually tailored to their wants and needs. For this reason, as residential contractors grow, they struggle to meet customers' demands for flexibility. This struggle to increase customization is not unique to the construction industry and many other industries have studied this problem in depth. While the inverse relationship between customization and cost is generally true, mass customization can enable increased customization with limited or no increased cost. The residential construction process employs many mass customization enabling principles, including modularity and product family design. However, the preconstruction process fails to employ these same principles. The purpose of this study was to explore how mass customization principles can simplify customization in the residential preconstruction process. Two rounds of interviews were conducted with residential construction industry preconstruction experts. Using their input, a process for implementing mass customization was developed. The results demonstrate that implementing mass customization principles can greatly simplify the purchasing, estimating, and option pricing processes for residential contractors. However, mass customization also significantly affects company structure, cost control strategies, trade relationships, and leanness. This research is enlightening to residential contractors struggling to manage customization. It also provides direction for software developers targeting the residential construction processes.