Abstract
The timbers as structural members in traditional Japanese wooden buildings provide important information at the time of construction such as the cultural and historical background. The main hall of Jyosho-ji Temple in Onomichi City, Hiroshima Prefecture (National Important Cultural Property), one of these traditional Japanese wooden structures, was built approximately 500 years ago, and its structural members have been used as they were when the temple was built. We conducted an investigation of 127 removed timbers considered no longer useful as structural members during the restoration of the main hall of Jyosho-ji Temple. The wood species, apparent density and annual ring width of each of these removed timbers were investigated, and cross-sectional photographs and optical micrographs of the three sections (transverse, radial, and tangential sections) of these removed timbers were taken.Of the 127 pieces examined, 118 were JI-DARUKI, 5 were TOSHI-HIJIKI, and 4 were HIEN-DARUKI. All the pieces were assumed damaged by Anobiidae. The results of wood species identification using optical micrographs showed that 119 of the 127 removed timbers were Japanese red pine (Pinus densiflora Sieb. et Zucc.) and the remaining 8 removed timbers were Japanese cypress (Chamaecyparis obtusa (Sieb. et Zucc.) Endl.). The apparent density of these removed timbers was similar to or higher than that of commonly distributed timbers of Japanese red pine and cypress. The mean annual ring width of the removed timbers was slightly wider in the red pine and almost the same for cypress compared to commonly distributed timbers. Among the Japanese red pine timbers, 55% were without pith, whereas most of the Japanese cypress timbers contained pith. An examination of the positions of the removed timbers in the main hall revealed that they were mostly located on the western and northern sides.
