The purpose of this study is to propose the decision making technique in roof waterproofing method at the early construction stage. Selecting the suitable construction method is difficult because of the complex interrelationships between many factors of influencing the construction method selection. This study presents an example of selecting suitable method by analyzing LCC (Life Cycle Cost) in roof waterproofing work. In this study, roof waterproofing method is analyzed by LCC(Life Cycle Cost) which is consists of the initial costs, running costs, and removal costs. Sheet waterproofing, membrane waterproofing and asphalt waterproofing costs are compared to select the most economic method. The result of this study revealed that considering LCC is useful in selecting the proper method in the construction work.