Long before the modern period, practice to provide a traditional house in an isolated place such as a small island mostly maintained the balance of natural resources and dwellers' needs. Yet, industrialization's arrival disrupts this sustainability by introducing modern building material from outside of the Island. What is supposed to be a simplistic building material cycle may be inverted to be a complicated cycle that can threaten the local environment. Koja Doi Island is also facing the same situation; its local stilt houses are gradually replaced by houses using modern and non-local building materials. Therefore, this research aims to identify and assess whether the building material on both traditional and modern stilt houses in Koja Doi Island practices a sustainable material cycle. Two research methods were used in this research; interviews and observation. Interviews served as the initial data collecting method to understand the history and construction method of stilt houses from time to time on the Island, whereas the observation was used to investigate the materials used in both traditional and modern stilt houses and to validate interview findings. The result reveals that the utilization of stilt house building materials in Koja Doi before the modern era corresponds with sustainable material cycle characteristics. On the contrary, almost none of the modern stilt houses has entered the demolition stage. Consequently, this research still yet to conclude that using modern building material in this Island considered non-sustainable.