Framework for Evaluating the Adaptability of Multi-Unit Housing for Sustainable Residential Development: Operationalization and Preliminary Evaluation Based on Beijing Case Studies

Family structures, lifestyles, and care needs change rapidly in high-density cities and reshape what residents require from their homes. Fixed layouts of standard multi-unit housing often fail to respond. Existing evaluation methods lack tools for assessing adaptability in terms of spatial organization and living experience. This study conceptualizes residential adaptability as the capacity to support both spatial variability and changes in residential relationships. Focusing on small-sized housing in Beijing, we used a literature review, expert interviews and housing surveys to derive evaluation indicators. We used 181 public weighting questionnaires and 32 expert analytic hierarchy process (AHP) questionnaires to determine the indicator weights, which we used to establish the Residential Interior Design Adaptability Evaluation System (R-IDAES). The system consists of four layers: a target layer, a criteria layer, an indicator layer and an assessment attribute layer. The abstract concept of residential adaptability is translated into identifiable, comparable and scorable indicators for spatial assessment. Interface, base plane, opening and circulation emerged as the key spatial elements in residential adaptability. The preliminary and refined schemes of three housing cases were further compared. An operational usability study with 12 designers and a supplementary psychological perception assessment with 13 residents provided a preliminary assessment of the framework’s feasibility. Within the three examined Beijing cases, the findings provide preliminary evidence that R-IDAES can assess the spatial adaptability potential of design schemes, identify low-scoring spatial attributes, and provide structured directions for subsequent design refinement.