As for the survey of Civil Engineering Heritage in Japan, it was started since 1989 for the modernized structures constructed after the Meiji Restoration, while it has been nothing done for the older traditional structures before the Restoration. The reason was quite simple. At that time, the modernized structures were considered in the critical situation of demolition and replacement so that it must have been taken preference over the older traditional structures constructed before the Restoration. We also considered those older structures had been survived more than 130 years, therefore they might have been preserved by the local people. However it was mistaken. We had seen so many cases that the older traditional structures were destroyed without any hesitation, because their value as historical monument were not defined and authorized at all. That is the reason why the authors have started this project.
The modernized structures and the older traditional structures are both civil engineering heritage, but there is a large difference among them especially concerning the condition of preservation. In the case of the modernized ones, it is quite necessary to survive almost whole part of structures when they are constructed. But, in the case of the older ones, such kind of restriction is almost nonsense, because the majority of surviving structures have been repaired and renovated up to nowadays.
In this paper, the authors try to show a proposal concerning “how to classify the degree of preservation of the older traditional structures before the Restoration, that is, constructed in the Edo period and prior to that” Before this trial, we have been done a survey covering the whole country. They are divided into three parts. The first one is the previous document study using, and the second one is the census survey for all the municipalities. The third one is more individual survey by limiting the objects. The proposal is made based on such experience