Earth lodges were typically constructed using a wattle and daub technique with a particularly thick coating of earth. The dome-like shape of the earth lodge was achieved by the use of angled or carefully bent tree trunks, although hipped roofs were also sometimes used. During construction, an area of land was first dug a few feet beneath the surface, allowing the entire building to have a floor somewhat beneath the surrounding ground level. Posts were set into holes in the ground around the edges of the earth lodge, and their tops met in or near the middle. The construction technique is sturdy, and can produce quite large buildings (some as much as 60 feet across) although size is limited somewhat by the length of available tree trunks. Internal vertical support posts were sometimes used to give additional structural support to the roof rafters.
After a strong layer of sticks or reeds was wrapped through and over the radiating roof timbers, a layer of thatch was often applied as part of the roof, although the structure was then entirely covered in earth. This earth layer provides insulation against extreme temperatures, as does the partially subterranean foundation.
Earth lodges were a common dwelling for Native American tribes of the upper midwest. Most specifically the Mandan, the Hidatsa and Arikara.
The origin of the upper midwest Earthlodge is generally attributed to the Mandan tribe, who were a sedentary farming and trading tribe. Later when the Hidatsa and then the Arikara came into the area they adopted the earthern structures.
These structures were a familiar site to traders and explorers along the banks of the little missouri, and were found in city clusters of up to a 1000 thousand such earthern homes.
These structures consisted of a clay outer shell, over an inner shell of long grasses and a woven willow ceiling. The very middle of the Earthlodge was used as a fire pit and a hole was built into the center. This smoke hole was often covered by a bullboat during inclement weather.
Logs were generally gathered each spring as the ice receded and sheared them off, fresh logs were also cut. The most common wood used, traditionally speaking, was Cottonwood. Cottonwood being such a wet and soft wood meant that lodges often required re-building every 6-8 years.
Many would be surprised to learn that the men only raised the large logs, and the rest of back breaking work was left to the woman. As such a lodge was considered to be "owned" by the female who built it.
A vestibule of exposed logs marked the entrance and provided and entryway, these vestibules were often a minimum of 6' in length to about 9' in length, which was determined by the size of the lodge and resulting outer clay thickness.
Generally a winbreak was built on the interior of the lodge, blocking wind and giving privacy to the occupants. In addition, earthlodges often contained Cache pits, or root cellar type holes, lined with willow and grasses - within which dried vegetables were stored.
They were most often found alongside tribal farm fields as well, alternating with tipis - which were used during the nomadic hunting season of the year. An entire Earthlodge village can be seen at New Town, North Dakota.
The village consists of six family sized earthlodges and one large ceremonial earthlodge. In addition, a garden area and horse corrals have been built to add to the authenticity. This park is open to the public and located west of New Town at the Earthlodge Village Site. The family Earthlodges are roughly 40' in diameter, while the Ceremonial Earthlodge is 90' plus in diameter, it is also the largest such structure in the world. The park is the central point in a rebuilding and cultural renewal effort by the Three Affiliated Tribes of the Fort Berthold Indian Reservation. This is the only village of its kind to be constructed by the Mandan, Hidatsa and Arikara nations in over a 100 years.
In addition, a reconstructed earth lodge can be seen at the Glenwood, Iowa Lake Park.
In Kanabec County, Minnesota, there is a Groundhouse River. According to Newton H. Winchell in The Aborigines of Minnesota, the river was thus named due to the earth lodges of the Hidatsa, who lived in the area before being driven westward to the Missouri River by the Sioux. The Hidatsa lived in wooden huts covered with earth.