Abstract
Since the Medieval Period, Japanese Buddhist arcitectures had the rafters precisely placed at regular intervals. And column spans were multiple of this length. This way to plase rafters called 'SHIWARI-SEF was closely connected with the whole planning method. Moreover, a measurements between rafters take fractional numbers. So there are important problems in this phenomenon for architectural planning method. This papers concerned with these problems, especially attempted to solve the problem regarding the fractional numerals which appear in inter-column and inter-rafter measurements as exemplified by Buddhist main halls. In the first half of the Medieval Period, We can confirm one of the basis for method of design for architectuer ; 1'JO' (丈), the absolute measurement, it is. The fractions that appear in measurements between rafters were brought by 1'JO' divided into numbers from 15 to 22 (excluding 21) equal parts. At least, we can recognize that these manipulasion existed in methods of design for Buddhist main halls in the first half of the Medieval Period.
