 Additional kinds of housing, especially for unmarried people, include boarding houses (which are popular among college students), dormitories (common in companies), and barracks (for members of the Japan Self-Defense Forces, police and some other public employees).An unusual feature of Japanese housing is that houses are presumed to have a limited lifespan, and are generally torn down and rebuilt after a few decades, generally twenty years for wooden buildings and thirty years for concrete buildings – see regulations for details.Figures from the 2012 Housing and Land Survey conducted by the Ministry of Internal Affairs and Communications indicate that Japan had 53,890,900 housing units at the time.