Non-wood building materials used in housing construction are dominated by a few domestic manufacturers, whereas products made by overseas manufacturers are rarely used. Although challenging to prove, an oligopoly keeps prices high. This study examines the impact of persistently high non-wood building material prices by analyzing their relationship with lumber prices. In addition, we discuss why non-wood building materials from overseas manufacturers have not been widely adopted by interviewing building contractors. The results of the analysis are as follows: (1) When the prices of fresh concrete, aluminum sashes, tiles, and metal kitchen sink sets that complement cedar, pine, and cypress lumber products decline, the price of lumber tends to increase. (2) Building materials are not imported due to a combination of market structure challenges, such as import duties and uncertain lead times, along with institutional barriers, including the difficulty overseas companies face in attaining Japanese industrial standards. While market structure issues can only be addressed by private companies, institutional issues can be resolved through policy changes. Increasing the possibility of importing building materials and reducing the oligopoly of building materials are crucial forestry policies.