This paper is to describe the development process of architectural sheet metal technology and to clarify how to use sheet metal in modern detached houses designed by architects in Hokkaido.
In Hokkaido, architects should pay special attention to the details of exterior because frost damage and deterioration due to the large temperature difference between inside and outside of the building are very serious. Consequently, houses in Hokkaido have developed in harsh climatic conditions, differentiated from traditional japanese houses in other regions over the years. For instance roof tile is not applicable to avoid the snow slide from the roof and it is indispensable to take air tightness, weatherability and insulation under cold climate into account. While there are various materials nowadays, sheet metal is the most relevant material in Hokkaido by such reasons, as well as the advantage in low cost and lightweight. This paper assumes that sheet metal technology has made its own development inevitably in Hokkaido responding to the specific climate conditions ahead of other regions in the modern period after World War II.
The authors know that early works by Akihisa Endo, Fujio Adachi and Naoaki Ogaki reported about houses in Hokkaido before 1970's focusing on remarkable plan types, space configurations, roof shape and so on. On the other hand this paper examines charasteristics of the exterior since 1980's, the period that the progress was made in the insulation technology.
Sanko Metal Industrial Co., Ltd., a major steel manufacturer in Japan, appeared in 1949. Sanko lead sheet metal industry then advanced to Hokkaido in 1950. It promoted mechanization of sheet metal production by "taking full responsibility for construction process". As a result, some sheet metal companies including Sanko associated voluntary organizations and created a total production and construction system and made contribution to the modernization of sheet metal technology corresponding to the social situation.
In this paper, the authors report three major notable issues as follows:
(1) While there were some independent craftsman unions in major cities, for instance, Sapporo, Otaru, Muroran and so on, they need to organize an integrated system which dominates such local unions to cooperate with each other. Two features were required, such as a hierarchical and cooperation system among several companies of production, construction and sale. Kitasanyukai established in 1960 is the most characteristic union. It contributed to achieve stable supply of sheet metal in Hokkaido.
(2) To prevent rain leaking due to the heavy snow, it is inevitable that sheet metal technology was well-developed in Hokkaido. Densification of the city is another cause for the spread of sheet metal technology since the snow slide from the roof cause troubles with neighbors and damage the windows, walls and so on. Corresponding to such circumstance, Sanko invented molding machine for long metal plate roof. Since then, various sheet metal methods, which make possible to design pitched roofs even in densely populated area, was made, such as Snow Stopper Roof produced by Makita Co., Ltd..
(3) Houses with pitched roof, one of the main feature of the original landscape in Hokkaido, increased since the range of choices of roof shape and roofing method extended. Moreover, architects managed and improved to use sheet metal in each parts of exterior and started taking advantage of various light reflection and so on.
Finally the authors concluded that sheet metal technology and craftmanship as well as craftmans unions in Hokkaido took a leading role after World War II.