Excerpts from the Shelter, copyright 1973 by Shelter Publications, PO Box 279, Bolinas CA 94924, a synopsis of material available from a number of publications.
The Mandans and Minnetarees of the Upper Missouri constructed a timber framed house ... the houses were circular in external form, the walls being about 5 feet high, and sloping inward and upward from the ground, upon with rested an inclined roof, both the exterior wall and the roof being plastered over with earth a foot and a half thick. These houses are about 40 feet in diameter, with the floor sunk a foot or more below the surface of the ground, 6 feet high on the inside at the line of the wall and from 12 to 15 feet high in the center. An opening was left in the center, about four feet in diameter for the exit of the smoke and for the admission of light. The interior was spacious and tolerably well lighted although the opening in the roof and a single doorway were the only apertures through which light could penetrate. There was one "Eskimo" doorway; that is by a passage some 5 feet wide, 10 to 12 feet long and about 6 feet high, constructed with split timbers, roofed with poles and covered with earth. The fire pit was about five feet in diameter , a foot deep and encircled with flat stones set up edgewise. Such a lodge would accommodate 5 or 6 families embracing 30 or 40 persons.