Kiwarijutsu is a Japanese system for building based on set proportions and modules. The dimension of any one member is related to all of the others in the design. For example, the width of a ken –the distance between pillars–would determine the width of all of its component parts (the pillars, for example) based on predefined ratios. The width of those components would, in turn, define the width of their components based on standard proportions.
The size of rooms were defined by the number of tatami mats needed to cover the floor space. The actual size of tatami mats varied from region to region and changed over time, but was consistent within the same building.
Using kiwarijutsu, carpenters could be assured that the proportions of the components in a building were architecturally harmonious. Moreover, the system promoted standardization of parts enabling daiku to work more effectively. According to Nishi and Hozumi, carpenters had considerable leeway in applying these rules. Kiwarijutsu provided carpenters with “guidelines to be learned, then creatively applied.”
Rules for building were recorded in books called kiwarisho beginning in the Muromachi period (1336 to 1573). These books were passed down as trade secrets within carpenter families.
