Sengu (遷宮)
A sengu is the temporary transfer of a shintai (an object of worship housed in a Shinto shrine and believed to contain the spirit of a deity). Sengu is conducted when the honden (main building) of a shrine is being built and repaired or when a new honden is being constructed. It refers to the construction, repair and reconstruction of the honden as well as its rites and festivals. Shosengu is a planned sengu. A karidono sengu is the transfer to a tentative building when a honden needs unexpected repair or reconstruction due to a natural disaster or other catastrophe. A rinji sengu is an extraordinary transfer, in which the same rituals are conducted as in a shosengu in order to transfer shintai to a newly built honden due to unforeseen circumstances. Sometimes, the sengu is classified as described above. The term "sengu" often refers to the jingu shikinen sengu of Ise-jingu Shrine (Ise City, Mie Prefecture). At all other shrines, sengu is sometimes differentiated from the concept of senza.
The main buildings of both the shogu (main shrine) and betsugu (auxiliary associated shrines) of Ise-jingu Shrine are in general subject to regular rebuilding efforts every 20 years; such renewals are called "shikinen sengu." The word "shikinen," when used in the context, means a fixed year. Sengu used to be conducted at Sumiyoshi-taisha Shrine (Sumiyoshi Ward, Osaka City), Katori-jingu Shrine, Kashima-jingu Shrine, Usa-jingu Shrine, Kasuga-taisha Shrine and Suwa-taisha Shrine (=>Onbashira-sai Festival). Yet the main building of Sumiyoshi-taisha Shrine has not been rebuilt since 1810, merely repaired on the occasion of the transfer of its shintai to a temporary structure. However, the term shikinen sengu is still in use today.
(The main building of Sumiyoshi-taisha Shrine has been designated as a national treasure, so it can't be reconstructed.)
Shikinen sengu is considered to be part of Shiki nen sai (religious festivals held on fixed years).
Small shrines also conduct sengu, as exemplified by Shinmei-jinja Shrine in Ago-cho, Shima City, Mie Prefecture, which has conducted a sengu every 20 years since 1764 in the mid-Edo period.