Architectural design and urban renewal that adapt to an ageing society and are localized are urgent needs around the world. On the other hand, the concept of grey space, which refers to transitional space and is an in‐between concept, has been proposed since the 1980s, but few studies have further explored its hierarchy, fluidity, and relationship with regional characteristics. Therefore, this study hopes to use the fluidity of the grey space hierarchy to solve the problem of design that adapts to an ageing society and preserves regional characteristics. This study mainly focuses on the spatial characteristics of Beitou Heart Village, summarizes five grey space hierarchies and fluidity modes, and finally designs social housing for young and old cohabitation in a bottom‐up manner based on them, restoring local unique neighborhood care and multi‐ethnic communication methods. There are three innovations in this study: (1) defining the division method of the grey space hierarchy; (2) exploring the richness and scalability of the grey space hierarchy in terms of fluidity; (3) using the grey space hierarchy to achieve neighborhood care and multi‐ethnic communication, making social housing for urban renewal more people‐oriented and retaining spatial regional characteristics. This paper may provide a theoretical foundation and practical help for grey‐space‐based design and urban renewal in the future.
