This thesis researches if the traditional Japanese woodworking technique, Kigumi, can offer a solution for a circular and biobased building industry. The construction sector is currently responsible for about 37% of global CO2 emissions. Although wood is a sustainable alternative to concrete and steel, circularity in modern construction is often limited by the use of glue and steel screws. These methods make it difficult to take buildings apart without damaging the wood, which makes reuse difficult.
Kigumi offers a unique solution by using complex, pure wooden joints without glue or metal. In this research, five case studies are analyzed from the ancient Hōryū-ji temple to modern projects like the Tamedia office building and the Expo 2025 ring. The research looks at the technical quality, the level of demountability, and the seismic resistance of these joints. An important part of the thesis is the
transition from handwork to modern technology.
While Kigumi could previously only be made by specialized carpenters (Miya-daiku), 5-axis CNC milling now ensures that these joints can be produced quickly, precisely, and on a large scale. The conclusion of this research is that the combination of old Japanese wisdom and modern robotics is a realistic path toward a sustainable future. It makes buildings fully demountable, allowing wood to be reused at a high level and drastically reducing the impact on the environment.