Mitsui Home’s “One Day Lock-Up” Construction Standard
Mitsui Home builds more than 6,000 custom-designed single-family homes per year in Japan. Virtually all of these homes are supplied on a “demolish and rebuild,” in-fill basis. In Japan’s residential areas, the streets are narrow and the lots are small. The space required to set materials for a conventional “stick-frame” construction process simply does not exist. Prefabricating as much as possible, combined with a world-class JIT delivery system, allows Mitsui Home to erect most of their custom homes to a “lock-up” condition in just one day. In many of Mitsui Home’s factories, the windows are also pre-installed in the wall panels. This “systemized” approach ensures (1) the highest possible construction quality; (2) the fastest delivery of the home to the home-owner; (3) the most efficient use of materials; (4) the most efficient use of site-labor; and (5) the least disruption to the community during construction, with heavy equipment at the site for only one day. Construction methodologies are evolving in many jurisdictions of the world. Prefabrication is a foundation element of systemization; and in systemization, design detail and accuracy is paramount.