In a different context, the user's needs in a housing apartment are constantly changing; it is required that the provided house, by having flexibility, can always be responsive to the user's needs in various situations, which would be a challenge for specialized areas of housing, including design. To perform a flexible housing design, the architects face many different design solutions and variables, leading to confusion in this field. So, the objective of this study is to identify these variables and achieve an effective solution by considering their priority of them. The variables of this study were proposed in three scales of macro, medium, and micro according to the previous valid research studies in the field of flexible housing. Then, the variables have been evaluated using the specialist's idea through the Fuzzy Delphi method (FDM). The Friedman test has been used to analyze the data obtained from the questionnaires and achieve a valid ranking, which performs the ranking by calculating the mean rank for each variable. According to the results of data analysis, the characteristics of "spatial expansion and division," which means the possibility of space to be expanded (the expansion) or divided (the contraction), as the medium scale of housing design, has the greatest impact on the housing flexibility. On the macro scale, the "structure" component, and the micro-scale, the "use of flexible elements" provide the highest effectiveness in this regard. Moreover, as the medium scale, the modular design of space falls in the second place of influence compared to all other variables. Increasing the properties of spatial expansion and spatial division can be an effective design strategy for achieving flexibility in apartment housing. Also, modular space designing and flexible elements have been introduced as two solutions in the next priorities. All are considered small and medium scales and can be prioritized in designing flexible apartment housing.
