Objective: The accelerated transformation of historic urban fabrics compels a critical reevaluation of contemporary approaches to their conservation and adaptation. The study of residential architecture constitutes a pivotal domain within architectural style research, offering novel perspectives for conceptual and design innovation. In the city of Arak, the evolution of residential architecture during the Qajar (1789–1925) and early Pahlavi (1925–1941) periods engendered significant structural metamorphoses in the physical fabric of historic houses. These transformations, manifested through shifts in primary architectural components—including massing, semi-open spaces, and open areas—resulted in distinct variations in spatial organization and formal typologies between the two eras. A precise understanding of these architectural changes not only aids in the preservation and revitalization of built heritage but also provides innovative strategies for future design practices.
This article analyzes architectural transformations in the historic houses of Arak across the Qajar and early Pahlavi periods, focusing on the evolution of closed, semi-open, and open spaces, as well as spatial and geometric reconfigurations. The study addresses two central research questions:1- How did the evolution of spatial hierarchies and functional allocations in Arak's historic houses unfold between the Qajar and early Pahlavi periods? -2- What were the transformative processes in the spatial-connectivity layouts of residential structures during this transitional era?
To investigate these spatial dynamics, 14 historically significant houses in Arak—7 from the Qajar era and 7 from the early Pahlavi period—were purposefully selected and subjected to comparative typological and morphological analysis.
Method: This study employs a descriptive-analytical methodology, utilizing statistical tools such as the Mann-Whitney U test at a 95% confidence level via SPSS software to systematically examine spatial-dimensional transformations in the historic houses of Arak across the two studied periods. The analysis focuses on quantifying shifts in spatial configurations, volumetric relationships, and typological patterns to derive statistically significant insights into the architectural evolution between the Qajar and early Pahlavi eras.
Results: Mann-Whitney U test results revealed statistically significant divergence (p < 0/05) in spatial allocation patterns between the two periods. Qajar-era houses allocated approximately 65% of total area to built mass, 7% to semi-open spaces (e.g., iwāns, verandas), and 26% to open courtyards. In contrast, early Pahlavi-period houses demonstrated a radical reconfiguration, with 37% allocated to built mass, 7% to semi-open zones, and 56% to open spaces—a near-inversion of spatial priorities.
Conclusions: Three housing patterns have been identified, in which the traditional "Courtyard-Veranda-Room" model has shifted to a "Courtyard-Room" model. These changes, along with variations in the ratio of enclosed and open spaces, reflect social, cultural, and technological transformations that have reshaped the Iranian way of life.