Theory of Open Building has been carried out for decades, its implementation varies according to different circumstances and conditions. As majority of urban living style in Taiwan based on collective housing and interior space often limited, the design approach referenced from the theory to construct flexible living style to maximize usable functional space in response to Family Life Cycle. Moreover, new definition of "home" should not only focus on predictable events, but to encourage opportunity of interaction between family members. This project is designed for client who is single and expecting marriage to form a new family. As theory of Open Building often refers to building modification and interconnection of structure, to fulfill requirements for changing is challenging. Therefore, this design aims to develop easy operation method to encourage users for space rearrangement. It does not only introduce quality of flexibility into fixed interior setting, but also try to maximum the usability of living space, thus to explore potential possibilities of new sustainable living style.