Japan Prefabricated Housing Development History: What Is Worth Learning-Ehang Container House

This article explains Japan's prefabricated (precast) housing through its definition, development history, results, construction-method categories, key traits, role in disaster relief, and future directions.

What Is a Prefabricated House

A prefabricated house is a system in which structural components (columns, beams, roof trusses, walls, and more) are produced in a factory and then transported to the building site for assembly.

The main advantages are quality control plus shorter construction cycles.

Development History

After World War II, Japan's housing shortage reached $5,833,333 units, which required accelerating large-scale housing construction.

1960s

Japanese housing companies and some construction firms jointly developed mid- and high-rise housing with PC (precast concrete).

The government set public-housing standard housing plans.

These methods made it possible to build large volumes of public housing.

1960s (continued)

Many companies entered the real-estate industry.

Some companies developed new housing systems and began selling detached low-rise prefabricated houses.

1970s

To design and build high-rise buildings more effectively, various PC technologies were developed.

The government ran development projects for prefabricated houses with better performance and lower cost.

The government launched an evaluation system for prefabricated houses.

1980s-1990s

The JPA (Japan Prefabricated Construction Suppliers and Manufacturers Association) launched a PC component quality certification program and a PC structure inspection system.

In 1995, the Great Hanshin Earthquake occurred; that quake proved that prefabricated houses can be very strong in a major earthquake.

21st century

JPA launched a PC building management engineer qualification system.

Some prefabricated housing companies developed projects overseas, including in China, Southeast Asia, Australia, and the United States.

Prefabricated housing companies focused on high performance—seismic resistance, energy efficiency, design for older residents, and durability.

From 1963 to 2014, Japan built about $1,250,000 prefabricated houses. Of these, concrete-structure homes totaled $222,917, wood-structure homes $213,056, and iron-and-steel-structure homes $827,500. Housing construction peaked in 1993.

Results of Prefabricated Housing Development

In recent years, Japan has built about 150,000 prefabricated houses each year.

Categories of Prefabricated Houses

Japan classifies prefabricated houses as:

Iron-and-steel-structure prefabricated houses.

Modular prefabricated houses.

Wood-structure prefabricated houses.

Concrete prefabricated houses.

Iron-and-steel-structure prefabricated houses

The steel frame includes the main structural members, using wall panels with steel-frame columns and beams. The usual process is to prefabricate part of the structure and walls in a factory, then transport them to the site for assembly to complete the whole building.

Modular prefabricated houses

Modules (units) made with steel or wood frames are produced in a factory and joined together on site. Interior finishing of the modules is completed in the factory. The share of industrialized production is high.

Wood-structure prefabricated houses

Structural members are wood panels and other wood products.

Concrete prefabricated houses

Structural members are precast concrete panels or other precast concrete products.

Traits of Prefabricated Houses

Stable quality with high precision.

—Cutting-edge technologies such as computers and robots strictly control factory quality.

Because components are standardized, simple yet high-quality work can be done on the construction site.

Construction schedules are greatly shortened.

—Less dependence on worker skill. Less on-site work. Owners can move in sooner.

Project costs can be reduced.

—Bulk purchasing of materials and standardized production work.

Valuable technologies and performance features are easier to adopt.

—Technologies and finishes that are hard to apply on site, such as special processing and coating.

Japanese prefabricated building cases

Prefabricated Houses in Disaster Relief

At the request of prefectural governors, the Japan Housing Federation builds temporary housing for disaster victims.

—Examples include the Great Hanshin Earthquake, the Mount Usu eruption, and the Great East Japan Earthquake.

The Japan Housing Federation has signed disaster-period temporary housing construction agreements with Japan's 47 prefectures. The table below summarizes the number of disaster-relief homes built each year since 1995.