The gasshou zukuri, or simply gasshou, are a type of minka, a general term used during the Edo Era to refer to any house belonging to the non-samurai classes. Gasshou usually applies to the farmhouses built in this style, but other structures not intended for living quarters may be built in the style too. The earliest examples are dated to the 17th century and are associated with the picturesque villages of Gifu Prefecture, like Shirakawa and Gokayama.
It was thought that the steep roofs provided practical protection against snowy weather, but it turns out there’s another reason for it. The spacious area under the roof was perfect for raising silkworms, and multiple slatted lofts were installed just for this purpose. The silkworm argument is further supported by the fact that re-thatching the enormous roof is an extremely labor-intensive process, requiring much more time, money and effort than it would to keep snow off a more modest roof.
Some gasshou zukuri may have had an additional loft for sleeping, but for the most part living quarters were located on the lowest floor, bungalow style. This is all the more impressive considering it was common for large extended families to live together in one unit. In some cases, as many as 30 people lived there together. Most gasshou-style farmhouses are now considered Important Cultural Properties, and some of the villages where they are found, like Shirakawa, have been designated UNESCO World Heritage Sights.