Public houses of wooden construction in Japan more vary in specification and construction method compared with those of the other structural type. Therefore many of the local governments, particularly small governments which are in serious financial condition and whose technical officials are limited, usually have some difficulty with selecting proper construction methods for refurbishing. It is necessary to understand what kind of refurbishing projects are implemented for wooden public houses and develop the findings into proper approaches for making a long-life refurbishment plan according to not only deterioration states but also kinds of specifications and building construction method.
This paper focuses on external wall refurbishments as one of representative large-scale refurbishment, and aims to clarify what construction methods for refurbishing external walls of wooden public houses were adopted by the local governments.
Based on the questionnaire survey, the authors show overall situation of managing public houses from the aspect of accounting situation, documents on repair and refurbishment history and performances of various refurbishment projects. With respect to the external wall refurbishment of wooden houses, they categorized the construction methods into three types: coating, replacing and covering, and analyzed how each type is likely to be adopted in terms of region and specification of external walls. Overall, performance rate of coating method tends to be higher in western Japan, and that of replacing or covering method tends to be higher in northern Japan like Hokkaido and Tohoku region. And covering was founded to be more performed than replacing, and metal or fiber reinforced cement sidings are likely to be adopted for covering existing wall of not only dry type wall (walls covered with siding, clapboard) but also wet type wall (walls of mortar, plaster).
The authors explored case of the 13 projects of external wall refurbishment by making interviews with the officials of the nine local governments and examined the records and documents relevant to planning for each project. They understand how each project was performed from planning projects to implementing construction works and describe the characteristics and problems of each type of refurbishing methods from the aspect of physical conditions of existing walls, cost composition, ancillary work and budgetary measures.
The findings imply a coating method (mainly application of wooden protective paint or sprayed-type coating materials) is likely to be adopted when the deterioration state of external wall is not serious. On the other hand, when it is serious, covering, which leaves existing wall unrepair and covers with complete new brandering and sidings, is likely to be adopted rather than replacing for some merits such as lighter burden on occupants and higher applicability to both dry type and type wall. However, there are some problems in covering including remaining of deterioration risk and highly individual design for waterproof and moisture emission.
were found to increase construction cost by hundreds of thousand yen per unit, it could make long-term overall cost for management reduced.
Refurbishing projects with ancillary work like replacing balconies and roof refurbishment can lead a sharp increase in overall project costs. It is possible that the number of feasible buildings for refurbishment projects is unavoidably reduced depending on budgetary system of local governments. It is necessary to strategically consider construction methods for refurbishment ensuring leveling-off of project cost as well as reducing the long-term management cost.