Before peaceful contact and sedentation on reservations the Ache lived in small nomadic bands that were highly flexible in composition, generally changing membership several times per year. The median size of precontact bands was about 50 individuals, with residential bands ranging from 3 to about 160 individuals on any particular day. These bands generally moved their campsite almost every day, but would occasionally stay in one place for a few weeks before moving on. Individuals knew the approximate location of neighboring bands and would visit them to share large kills or to search for romantic opportunities. The only time most of the members of the twelve or so Northern Ache bands would come together in one place was at prearranged puberty ceremonies and club fights. Campsites were located almost anywhere throughout the home range of a group, and fully adult members of the Northern group report foraging over an area of about 18,500 square kilometers in their lifetime. Despite their nomadic character, most Ache bands did have core areas that were exploited more frequently than the entire range of the group.
Campsites were generally located within 50 meters of good patches of palm trees that could be exploited for their fiber and heart. When large animals were killed, however, camp might be set up within a few meters of the kill site so as to avoid transporting the game. Water is abundant throughout eastern Paraguay and does not generally constrain the choice of a camping spot. Forest camps generally consist of five to ten fir hearths laid out in a circle with about 2 meters between each. The Ache sleep on the bare ground, on palm leaves and ferns, or on palm-leaf woven mats. Closely related family members or friends sleep together at the same hearth. Sleeping arrangements vary daily and are highly flexible. In precontact times, adolescent males were sometimes made to sleep in the center of a camp.
Small huts are made only when rain is imminent. These consist of four corner posts, two crossbeams, and a few dozen palm leaves laid flat across the crossbeams to shelter occupants from the worst of the rain. Current Ache reservation settlements have several hundred inhabitants, and wood-board-or bamboo-walled houses are spread out over several hundred meters. Each dwelling at the reservation houses one or more nuclear families and, often, visiting children, adolescents, relatives, or friends. Current reservation household composition changes almost weekly, and many individuals do not reside with their own nuclear family members.