This paper presents a new design methodology for improving the installation of large size and long life cycle goods that need to be assembled in the field. The approach integrates a modified design for assembly (DfA) methodology. A new approach is proposed for integrating different DfA methodologies and tested in a real case study of a machine room-less (MRL) elevator. A tool for analyzing and quantifying the proposed solutions is developed. Improvements of approximately 20 pp are achieved during the elevator installation and on-site assembly process, which could mean a potential reduction in assembly time of 11 h or 6%. Additional extensions and guidelines are recommended to improve the methodology and the tool.