Hamlets ( buble ) of eight to twelve dwellings, housing a total of thirty or more people, are built on hillocks on the sides of valleys. The houses ( bale ) are built on terraces close to rice fields. They and the granaries are made of timber and rest on four posts, with thatched roofs; the only difference in design between the two is that houses are larger and have hearths. There are also temporary buildings, such as houses for the unmarried, which are built on the ground. Houses once had a shelf for the skulls of enemies taken in battle. The typical household consists of the nuclear family; once children are old enough to take care of themselves, they go to live in boys' houses and girls' houses.