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.

  • Quality

    Optimizing a building’s framing solution is best achieved through today’s best-in-class prefabrication software. Full consideration of seismic, MEP and backing requirements, EWP optimization, and infeasibility discovery are high-value benefits.

  • Quality

    In today’s five- and six-story wood-frame buildings, there is no room for imprecise construction. The demand for precision in load-path design, seismic imbed systems, and framing is much higher than it used to be – which it absolutely should be.

  • Quality

    Wall panels have been available to wood-frame construction projects for decades. But prefabrication can go so much further with stair panels, floor panels, and prefabricated roof-sections. Preinstalled windows in wall panes is a well-proven system.

  • Quality

    Backing for handrails, grab-bars, cabinets, and bathroom fixtures can be preinstalled in panels to provide another level of value and time-saving in the construction process. All factories have an abundance of short material so adding backing optimizes overall material use.