The shrine buildings at Naiku and Geku, as well as the Uji Bridge, are rebuilt every 20 years as a part of the Shinto belief of the death and renewal of nature and the impermanence of all things (wabi-sabi) as a way of passing building techniques from one generation to the next. The next scheduled rebuilding of Ise Shrine is due in 2013.
These portable shrines are made by carpenters (Miya Daiku) on leisure time.
Miya Daiku: So-called "Miya Daiku", translated into English as "shrine carpenters" are traditional carpenters who design and construct shrines and temples in Japan. Miya Daiku is a profession separate from conventional house carpenter.