The Engawa as Spatial Mediator: Transformation of Design Mechanisms in Japanese Teahouses

The engawa, a threshold space in traditional Japanese architecture, has been widely cited as the archetypal manifestation of Kurokawa’s grey space theory. However, prevailing interpretations treat it as a static prototype, overlooking the transformation of its spatial mechanisms across history. The present study addresses this lacuna through a comparative case analysis of three representative teahouses. The following three styles are examined in this study: the sixteenth-century sōan style, the early seventeenth-century samurai style, and the early seventeenth-century shoin-zukuri style. The evolution of the engawa’s mediating function is traced through these three styles. An analytical framework comprising five dimensions—boundary permeability, sequential flow, material tactility, integration of natural elements, and visual transparency—is applied consistently across all cases. The analysis demonstrates a discernible evolutionary trajectory, commencing with an inwardly contracting spiritual threshold in Myōki-an, progressing to an outwardly differentiating social interface in ma, and culminating in a meticulously crafted aesthetic artefact in Mittan. The present findings demonstrate that the engawa is not a fixed spatial prototype but rather a dynamic mediator whose form adapts to shifting social, cultural, and spiritual demands. The study posits that the essence of intermediary space does not lie in any specific configuration, but rather in its capacity to mediate between opposing realms, including self and nature, individual and society, and function and beauty. This reinterpretation provides a theoretical foundation for contemporary architectural practice, proposing that designers should prioritize diagnosing the relational challenges that intermediary spaces are designed to address, as opposed to merely imitating historical forms.