Privacy, as one of the fundamental concepts in Iranian–Islamic architectural thought, constitutes a multilayered spatial and cultural structure that emerges from the interaction between physical organization, social values, and ethical meanings embedded in everyday life. In traditional Iranian residential environments, privacy has never been limited to a simple physical separation between interior and exterior spaces; rather, it represents a complex system of spatial hierarchy, controlled accessibility, visual management, and cultural norms that collectively shape the experience of dwelling. Despite the conceptual richness of this notion, a considerable portion of previous architectural studies has approached privacy primarily through isolated physical indicators such as enclosure, spatial boundaries, or visual barriers. Such approaches, although valuable, often overlook the causal and configurational relationships among multiple spatial attributes that jointly produce the condition of privacy within residential architecture.

The present research aims to identify and analyze the causal relationships among the five principal indicators of privacy within the indigenous residential architecture of South Khorasan Province in Iran. This region provides an appropriate context for investigation due to the persistence of traditional housing patterns and their strong adaptation to environmental, cultural, and social conditions. By examining these houses, the study seeks to reveal the underlying spatial logic through which privacy is constructed and maintained in vernacular architecture, and to explore how these spatial mechanisms may contribute to contemporary architectural discourse.

Methodologically, the research adopts a quantitative approach based on fuzzy-set Qualitative Comparative Analysis (FSQCA), which allows the identification of complex causal configurations among multiple variables. Unlike conventional statistical methods that often focus on isolated linear relationships, FSQCA enables the analysis of combinational causality, recognizing that architectural phenomena frequently emerge from the interaction of several spatial conditions simultaneously. The analytical process was conducted using the FSQCA software environment to evaluate causal relationships among the defined indicators of privacy.

Data collection was carried out using a structured questionnaire designed on a seven-point Likert scale to measure the presence and intensity of the selected privacy indicators in residential spatial configurations. The validity of the research instrument was confirmed through expert evaluation by three specialists in the fields of architecture and urban studies. Reliability testing was performed using Cronbach’s alpha coefficient, which yielded a value of α = 0.83, indicating an acceptable level of internal consistency for the measurement tool.

The statistical population of the study consisted of 148 indigenous residential buildings located in various settlements across South Khorasan Province. Based on Cochran’s sampling formula, 117 buildings that met the required criteria were selected as the final research sample. These buildings represent a diverse set of traditional residential forms that collectively reflect the spatial principles and cultural values governing vernacular housing in the region.

The findings of the analysis demonstrate that privacy in the indigenous houses of South Khorasan is not the outcome of a single spatial feature but rather the result of a coherent combination of spatial hierarchy, controlled access, spatial layering, and the strategic arrangement of public and private domains. Elements such as entrance sequences, transitional spaces, courtyard organization, and indirect visual corridors play significant roles in regulating movement, visibility, and social interaction within the domestic environment. The results of the fuzzy-set comparative analysis further reveal that specific configurations of spatial indicators consistently lead to higher levels of perceived privacy.

Moreover, the study indicates that traditional houses in the region employ subtle yet effective spatial strategies to mediate between collective life and individual privacy. These strategies include gradual transitions between public and private zones, the use of intermediary spaces that filter social interaction, and the deliberate orientation of openings and circulation paths to control visual exposure. Such spatial arrangements demonstrate that privacy is deeply embedded in the architectural logic of vernacular dwellings rather than being imposed as an external design constraint.

From a broader perspective, the research suggests that the spatial principles underlying privacy in traditional Iranian houses possess considerable potential for informing contemporary residential design. As modern housing developments increasingly face challenges related to density, social interaction, and personal space, revisiting the spatial intelligence embedded in vernacular architecture may provide valuable insights for creating residential environments that balance openness with privacy.

In conclusion, the study highlights that privacy in the indigenous residential architecture of South Khorasan represents a coherent and analyzable spatial system shaped by cultural norms, environmental adaptation, and architectural organization. By employing a fuzzy comparative analytical framework, the research provides a deeper understanding of how multiple spatial factors interact to produce privacy within domestic environments. These findings contribute to the theoretical understanding of privacy in architectural studies and offer practical implications for integrating traditional spatial wisdom into contemporary housing design.