Jomon Pit Dwellings

Jomon pit dwellings are the semi-subterranean houses of Japan's Jomon period (about 13,000 to 400 BCE). In Japanese they are called tateana (竪穴) dwellings, also written dateana tatemono. A shallow oval or round pit was dug, posts were set in the floor, and a roof framed on those posts was brought down to the edge of the pit. The type was not new to the Jomon: pit dwellings have been traced back to Palaeolithic sites in Hokkaido and Kyushu.

Sannai-Maruyama

The Sannai-Maruyama site in Aomori was occupied from the Early to Middle Jomon, about 3900 to 2200 BCE. With 648 pit dwellings it is one of the largest Jomon settlements known. Early dwellings were usually about 3-4 m (10-13 ft) across.

Around 2900 BCE the settlement added other building types:

• Raised storehouses on pillars, without fire pits, replacing storage pits.
• Longhouses, large oval buildings, the longest about 32 m (105 ft) long, used while pit dwellings continued.
• A six-pillar structure, built around 2600 BCE, of six chestnut posts about 1 m (3.3 ft) in diameter in two lines 4.2 m (13.8 ft) apart, set in holes 2 m (6.6 ft) wide and deep. Only the waterlogged bases survived.

Goshono and earth-covered roofs

At the Goshono site in Iwate, from around 2500 BCE, more than 800 pit dwellings have been found. Most were supported by four or six pillars set in an oval pit, with eaves reaching the upper edges of the pit so that the house looked like a low mound. Each had a hearth, and some may have had a loft-like storage space.

Jomon pit dwellings were long assumed to be thatched. Studies of burned houses at Goshono suggest that some instead had roofs of packed earth laid over the timber frame. The charred remains of one dwelling about 4,200 years old are displayed under a glass floor in the Goshono Jomon Museum, and several houses have been rebuilt on the site with earth roofs.

World Heritage

Sannai-Maruyama and Goshono are among the Jomon Prehistoric Sites in Northern Japan, inscribed on the UNESCO World Heritage List on 27 July 2021.

Significance for roofing history

The Goshono evidence is a reminder that reconstructions often default to thatch because it is familiar, while the archaeological traces can point elsewhere. Earth over timber, as in the later Plains earth lodge and in turf-roofed houses of northern Europe, gives insulation and fire resistance at the cost of a heavy load on the frame.