JAANUS / itabuki 板葺

itabuki　板葺

KEY WORD :　architecture / general terms / folk dwellings

Wood shingles. Widely used in Japan for buildings of many kinds, ranging from palaces, elite residences, shrines and temples to ordinary houses *minka 民家. Itabuki is believed to have been used at a high social level as early as the Asuka period. On vernacular houses, it was particularly used in mountainous areas where material for thatch was relatively hard to obtain. In urban districts it was gradually displaced during the last years of the Edo period by tile, which was both fireproof and longer lasting (itabuki roofs lasted about 30 years). Generally, the shingles were made from a log split first into quarters along the grain, and then cut or split (with wedges or a hatchet nata 鉈) into progressively thinner boards. These were less than 75mm thick, and their width was less than three times their thickness. The preferred materials were cedar *sugi 杉, sweet chestnut kuri 栗 and chamaeciparis pisifera sawara 椹. Reddish, sinuous lumber was preferred. Shingle types, in declining order of quality, included: tochi 栩, tokusa 木賊, masa 柾, koba 木羽, and kokera 柿. It is clear from a comparison of early medieval itabuki on vernacular houses, as depicted in illustrated handscrolls *emaki 絵巻, and itabuki shown in late Muromachi to Momoyama period painted screens *byoubu-e 屏風絵, that there was a general tendency for the shingles to get smaller. In the late Heian period, the distance from ridge to intermediate pillars *irigawabashira 入側柱, and from intermediate pillars to outer pillars *kawabashira 側柱 were each spanned with a single long shingle. In the Momoyama period, four or five shingles seem to have been enough to cover the distance from ridge to eaves, suggesting that the length of individual shingles was reduced by half. By the later Edo period, large shingles averaged between 45-85cm in length by 9-15cm in width by 1cm thick, while small ones averaged 30cm in length by 12cm in width by 3mm thick. Roofing undertaken with the larger type is called *naga-itabuki 長板葺, and with the smaller, ko-itabuki 小板葺. Doubtless dwindling timber resources led to this diminution in size. From medieval times, however, small shingles came to be used in more refined itabuki roofs on elite residences, shrines, and presumably developed to simulate the effects of cypress-bark roofing *hiwadabuki 桧皮葺. In these roofs, the lap of the shingle courses was far greater. A variety of names were used for such roofs, according to the detail and the type and thickness of the single, but the best known are *tochibuki 栩葺 and *kokerabuki 柿葺. Other forms of itabuki include sogibuki 殺ぎ葺, noshibuki 熨斗葺, *yamatobuki 大和葺, *odawarabuki 小田原葺, tontonbuki とんとん葺 and *ishioki itabuki 石置板葺. The character of itabuki roofs varied from the most curvaceous elegance possible, kokerabuki, which could be used for nearly any shape of roof, to the straight, shallowly pitched roofs of ishioki itabuki houses, which were almost invariably gabled *kirizuma yane 切妻屋根. Fixings as well as shingle size had much to do with this contrast: kokerabuki shingles were held in place with bamboo nails, while ishioki itabuki was held in place with stones. Roofs could not be steep or the stones would roll off.

Old Tanaka 田中 house (Gifu)
Hida minzokumura・Hida no sato　飛騨民俗村・飛騨の里 (Gifu)

REFERENCES:

*itabuki yane 板葺屋根, *kure 榑　

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