Thatched roofs in Japan come with considerable merits in addition to the obvious aesthetic ones…
Among Japan’s rich and varied clutch of World Heritage Sites, there are the monumental and there are the natural. But the one site most closely related to the way of life of ordinary Japanese is that of Shirakawago and Gokayama. These areas of remote mountain villages in Gifu and Toyama Prefectures are noted for their huge traditional gassho-zukuri farmhouses—some over 250 years old. Gassho-zukuri means “constructed like praying hands,” and it aptly reflects the fact that the roofs are steeply pitched at 60°–70° to withstand the region’s extremely heavy winter snows. The villages are a popular tourist attraction, but the most fascinating time to see them is when over 200 villagers join collective force in the business of thatching.
That rethatching on a house has to be done about every fifty years, and it takes the villagers—men and women, young and old—a couple of days to tackle the 19-meter-high roofs with surface areas of around 600 square meters. Without this cooperative system involving all able-bodied villagers, even a big family would need several months to complete the job. The rethatching of the gassho-zukuri is a rare, spectacular sight, but what those villagers do on that scale was once commonplace, albeit as smaller operations, throughout Japan.
Until around the early sixties, thatched houses were often encountered in Japan’s countryside. But then, as the economy boomed, house owners started to trade traditional thatched elegance for modern convenience in the shape of ceramic-roofed houses. However, as with many things, convenience sadly does tend to come at the price of diminished character. It was in fact the Shirakawago villagers’ alarm at the ugly proliferation of steel, glass, asphalt and neon further down their valley that they decided to establish a charter whereby they pledged not to sell or pull down their houses, thus preserving their remarkable structures for posterity.
The prime material that goes into thatching—two types of plume grass known as susuki and ogi (species of Miscanthus)—was at one time specially grown for the purpose in communal fields on the outskirts of villages or on nearby steep slopes in more mountainous areas. Every autumn, the reedlike herb would be harvested and stored in bundles and dried in barns until needed for roofing.
A roof that has been thatched well requires little maintenance, though a common feature of traditional Japanese houses helped promote the longevity of that thatch. The open hearth known as the irori, which lacked a chimney, was often the only source of heat in such a building, and it functioned as the center of family life. As well as being used for cooking, the irori supplied the smoke that would rise and form a black carbon coating on the wooden latticework under the roof. That carbon layer preserved the wood by warding off invasions of termites and mold, and it also helped prevent rotting of the thatch. However, all that carbon also sees to it that people undertaking thatching work among the beams soon look as if they have just emerged from a long shift down the coal pit.
Thatched roofs in Japan come with considerable merits in addition to the obvious aesthetic ones. The excellent insulation provided by the pockets of air among the straw bundles in the thatch ensures that the building is warm in winter and cool in summer. And for anyone who has suffered the depredations of Japan’s hot summers or shuddered in its winters, it is a wonder that this is not now a nation of thatched-roof structures.
In addition to the energy savings in heating and cooling, there is a great deal to be said for thatching in this age of growing eco-awareness. The production of plume grass results in zero carbon dioxide emissions: instead, the plant absorbs the greenhouse gas as it grows. Such roofing materials as ceramic tiles require energy and emit carbon. And when the thatch becomes waste, it can be returned to the land, decompose and gradually become soil. Or even if it is burnt, as in a thermoelectric power station, the result is a zero-emission footprint through the carbon absorbed during growing.
David Capel is a journalist living in Tokyo.
This article first appeared in the April 2013 issue of the Japan Journal. Updated for TJJ ONLINE, April 20, 2021.