Open Housing System ideas were developed in Korea in the 1980s to satisfy the demand for variety indwelling spaces. This domestic attempt to apply open building principles was highly restricted and was applied only in support of middle-large size apartments rather than small size apartments. One of the problems was the conventional design of building structures. It was difficult to effectively satisfy the various lifestyles and transformation of dwellings because existing apartments were designed using a concrete wall structure approach, in which room sizes and arrangements were fixed by the placement of structural concrete walls. This was the result not only of structural analysis (other structural designs were possible) but also the result of the idea that the standard plan was suitable for a stable society and was easier to implement, and that change in social standards and technical upgrading was not going to happen. This study presents an apartment concept in which open building design methods were applied to satisfy the problem of various lifestyles and household sizes and preferences for small apartments. This concept also helps to create a more effective and long lasting building which decreases construction waste, saves resources and protects the environment by enabling the building to accommodate combining, increasing / decreasing, changing location or changing usage of rooms.