Middle area. In upper class residences especially from the Momoyama period and through the Edo period, seating was determined by rank. The highest place was called *jōdan 上段. The middle area was below the highest step but above the lowest step *gedan 下段. This arrangement established seating strictly arranged according to rank, with the highest ranking persons occupying the uppermost level, those holding middle ranks sat in the chūdan, and the lowest ranks in the gedan.
The difference in height amounts to about 15 cm. The system of stepped-floors was already in use in the Momoyama period. The names, chūdan and jōdan are found on a drawing, dated 1588, of the plan of the large reception hall Ōhiroma 大広間 in the Jurakudai 聚楽第, a castle built for Toyotomi Hideyoshi 豊臣秀吉 (1536-98). The drawing is in the collection of the Kishigami 岸上 family. Further examples of the large reception hall in the main compound *honmaru 本丸 of Edojō 江戸城 are seen in a cross section drawing at Nishi Honganji 西本願寺 in Kyoto. The Shiroshoin 白書院 actually contains floors in three steps but the term chūdan does not appear.