Objective: The aim of the present study is to identify the criteria influencing residents' satisfaction based on the quality of space in the interior of apartment housing. The reduction in the size of spaces in apartments makes residential interiors with spaciousness desirable for residents. Among the spatial indicators that contribute to the spaciousness of the interior and lead to satisfaction with apartment housing is the use of spatial quality. Method: The research method is based on a mixed approach and utilizes two quantitative and qualitative phases. The quantitative phase of the research was conducted in two rounds using the Delphi method by surveying experts to refine the components of space quality. The statistical population of the quantitative phase of the research is 20 members of the faculty and architecture experts who were selected based on snowball sampling. The data related to the quantitative phase were analyzed in Spss 26 software and based on exploratory factor analysis. The qualitative phase of the research is based on the phenomenography approach, which was accompanied by a semi-structured interview based on targeted sampling of 15 residents based on their lived experience in common apartment housing in Borujerd city. The data of the qualitative phase were analyzed based on thematic analysis. The research setting is the common residential apartments in Borujerd city. Results:The findings of the present study indicate that out of the 25 spatial physical components of spatial quality identified from the research literature, 7 spatial physical components are influential on residents' satisfaction based on the perspective of experts; furthermore, in addition to the 7 components mentioned based on the perspective of experts, 3 other spatial physical components contribute to residents' satisfaction with the interior space of apartment housing.
Conclusions: The results of the research indicate that the use of components of space lighting, view to the open space, spatial opening, flexibility, organization of openings, spatial continuity, proportions of floor and ceiling, spatial dimensions, spatial organization and spatial details and the criteria related to each of these components leads to the satisfaction of residents from the interior space of the apartment housing.