Deterioration of the Wall of a Historic Stone Building in a Cold Region and Measures to Protect it

In the northern part of Japan, the air temperature decreases to -10 degrees Celsius in the winter. The outside walls of historic stone buildings deteriorate due to frost damage. We studied the deterioration of historic buildings and their environmental conditions in Otaru and Sapporo in Hokkaido. This paper reports on the observation of the deterioration of the building materials of an important cultural property, the Nihon Yusen Building. We also measured the temperature and humidity inside and outside the building as well as the water content of the wall surface. From these observations, it was revealed that the main cause of deterioration was damage to and rusting of the roof and chimney, which allowed rain water and snow-melt water to enter the rooms. The speed of deterioration is considered to be increasing. In particular, parts of the outside stone wall made of Otaru tuff under the roof on the north, west and south sides have deteriorated; this phenomenon was not observed at the time of the previous restoration. Rain water had penetrated into the stone mainly through the deteriorated part of the roof and rain water gutters as well as through the deteriorated part of the outside wall. Part of the water that had penetrated remained under the roof, on the borders previously mentioned, and between the stone blocks. The freeze and thaw cycles of the water in these areas caused the deterioration of the building materials in winter. As a protective measure, it is necessary to prevent the penetration of water into the building materials so as to avoid frost damage in the winter. It is also necessary to restore the roof, chimney and rain gutters immediately to prevent further damage to the building materials.