As the objccts of present study the writer has selected Bittschu area, lying the west of Okayama Prefecture and having the Takahashi River in its central part. He has studied its rural houses from the point of materials for thatching, roof forms, the arrangement of rooms and the difussion of techniques in thatching.
1) Materials for thatching roofs
This area can be classified into miscanthus thatching, miscanthus and straw thatching and straw thatching areas. Miscanthusthatched houses are found in the Chugoku Mountains and in the northern part of the Kibi Tableland, where miscanthus can be most easily obtained. Miscanthus grows in the tracts commonly owned by the people. They make it practice to co-operate in thatching their houses. In most of the Kibi Tableland where a straw is grown better than a miscanthus and a miscanthus alone is not sufficient for thatching, miscanthus and straw thatching can be seen, while in the plains of the south where there is no miscanthus but plentiful straw, straw thatching is generally practiced.
We can find a close connection between the geographical features …………… the Chugoku mountains, the Kibi Tableland and the plains in the south ………… and the materials for thatching roofs.
2) The roof forms
There are three classes of roof forms ……… irimoya roof, yosemune roof and gable roof. In Okayama Prefecture, many irimoya roofs mixed fewer yosemune roofs, and here and there tiled gables, but hardly straw-thatched ones are seen. Irimoya roofs are chiefly found in the Chugo kuMountains and the Kibi Tableland, while in the middle and southern section of the Kibi Table-land irimoya roofs are mixed with yosemune. The further toward the south wego down, the smaller gables become, and in the Kojima Peninsula, the extreme south, only yosemune roofs are found. In regard to the roof ornaments, they are simple in the Chugoku Mountains, complex in the Kibi Tableland and simple again in the plains of the south. The most striking ornaments of gables are openworks of a letter “water” or of a family crest found in the Chugoku Mountains and the north-west section of the Kibi Tableland.
3) The arrangement of rooms
Ordinarily four rooms are common, but here and there irregular ones are also found. In the north there is a hearth. In the central part also, once there must have been a hearth. That is testified by the presence of a wooden floor. Formerly a barn was established within a house. But later, it was built independently outside the house, leaving a large earth floor behind. A wooden floor was fixed where the earth floor had been. Thus the hearth, which had been in the middle room, was moved to a newlymade woden floor.
In Okayama Prefecture cattle have been kept in a main house except in the central and southern parts of West Bittschu.
As for pillars in a house, chestnuts are chiefly used as materials in miscanthus and straw thatching area as well as in miscanthus area, while Japan ceders or pine trees are used in straw thatching area. Pine trees are generally used for the upper part of a house. An old style buildig, in which pillars are directly erected on the foundation, still remains along the coast of the Inland Sea.
4) Diffusion of the technique in thatching roofs
It seems that they thatched their roofs in co-operation. Since Meiji Era so-called Geishu Roofers, ……… most of them were natives of Hiro village ……… have been working all over Okayama Prefecture away from their home. Some of them have settled down and been training their apprentices. Carpenters also diffused all over the prefecture. Many of the shrines were built by Shiaku carpenters, who, the writer supposes, have had some effect upon rural house type. However, only small number of them have penetrated deep into the north, so

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