The traditional construction method, widely used for Japanese wooden houses, is the framework system developed mainly for sukiya (tea-ceremony houses) and minka (private houses). The sukiya-style is designed to prevent deformation of columns and beams connected by carefully worked joints, nuki (batten) and uchinori-nageshi (heat jamb). The design allows the construction of y~~e~~~e (hip roof) or irimuya (jerkin-head roof), which are not dependent on other structures and are free from deformation. The uchinori-nageshi offers moderate partition and overlap to the flexible and portable space of the Japanese houses as well as to the lifestyle and culture. On the other hand, the minka style was developed in a variety of sturdy construction systems with regional characteristics. The frameworks skilfully limit the number of planes of the structure in order to conform to the unique Japanese concept of living space and lifestyle. For example, there is a construction system called wakuno-uchi used in the Hokuriku region of Japan in which the design can be varied by having a structural frame unit of centrally-placed nuki and sashikamoi (mortice and tenon head-jamb), around which geya (lean-to roofs) are constructed. In contrast to these traditional construction systems, contemporary construction methods for Japanese wood-framed houses are simple and safetyoriented against ho~zontal loads such as earthquakes and winds; the two-storey houses are the mainstream now in the wood-framed houses, and the methods are generally accepted in the large areas. However, wood members are slender and the joints are mainly designed to support vertical loads, with the failure of members prevented by metal straps, and deformation of the planes of the structure prevented by struts. While both the sukiya and minka styles have flexible or semi-rigid joints and cope with loads by the deformation of the materials or the joints, the contemporary system is a mixed flexible-rigid system necessitating a balanced placement of struts. It should be pointed out that this leads to inadequate fire resistance, especially of the structural members. It has been said that the construction of Japanese wood-framed houses is stagnating technologically because of too much standardisation of the construction methods, which was prompted among carpenters and architects, but did not give them any room to develop their own designs and construction methods. The two-by-four frame-and-panel construction system became popular because of the circumstances outlined in the preceding paragraph. Several attempts had been made to diffuse this construction system in Japan in the past, but only with the latest attempt about 10 years ago did it start to pervade the Japanese market. There were various reasons for its popularity, such as the stagnation of wood-frame construction technology in Japan, a shortage of materials, the maturity of housing industry organisations, and so on. Recently, the two-by-four construction system has been developing as a large-panel system with computer-aided design and manufacturing (CAD/CAM). This construction