Investigation of durability of wooden houses used for 100 years: State of moisture content of members and decay situation
2007
Nakatani, H.(Toyama-ken. Forestry and Forest Products Research Center, Imizu (Japan)) | Hata, M. | Wakashima, Y. | Sonoda, S.
To obtain methods to lengthen the life of houses, we investigated dismantled houses that used traditional construction methods that had been used for a long time in Toyama prefecture. This house was composed of parts that exceeded 100 years and a rebuilt part that was 32 years old. We inspected the moisture contents and Pirodlin value to measure the decay level for the primary members. Furthermore, we carried out bending tests for all columns. This house was constructed with a traditional structure called 'wakunouti' without any bearing walls. Therefore, this house possessed characteristics for a long-lived house, which can be inspected and decayed members can be easily exchanged, and room changes can be made corresponding to changes in the household life. The moisture content of members in the investigated house was high, because of the environment which had high humidity. The moisture content increased with the direction from the upper part of the house toward the ground. It was about 15% in the beams, 20% on average for the pillars, and it reached as much as 23% for members below the floor level. The columns on the inside of the house, and outer wall on the south and west were decayed slightly at the leg, though there was no decay in the upper part. On the other hand, the pillars of the outer wall on the north and east were notably decayed, and showed very high moisture content. It seems that the Pirodlin value was connected with the degree of the decay of the columns, and was correlated with moisture content. Although Pirodlin inspection is effective in quantitative evaluation of the degree of decay, it is thought that in situations of high moisture content it is possible to first check for decay.
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