A relational framework for interstitial urban geographies: Belfast’s Shankill-Falls interface

Urban theory has long treated interstitial spaces, gaps, vacant lots, buffers, and residual land as anomalies to be resolved through infill and redevelopment. This epistemology of “fullness” obscures how such spaces actively mediate relations between the neighbourhoods they separate. This article reconceptualises interstitial spaces as relational formations rather than residual voids. Drawing on relational spatial theory, it advances a three-domain framework (structural, ontological, and unifying) for analysing how intra-urban boundaries simultaneously separate and connect communities. The analysis focuses on Belfast’s Shankill-Falls interface, a spatial in-between space and peace wall separating Protestant/Unionist and Catholic/Nationalist communities since the Troubles (1968–1998). As one of Europe’s most enduring intra-urban boundaries, the interface provides an analytically generative case for examining how division and relation coexist. Drawing on semi-structured interviews, planning and policy documents, and site-based observation, the paper demonstrates how structural configurations, ontological ambivalence, and relational practices produce a type of physical division that structures rather than precludes everyday relations. The paper contributes a transferable framework for rethinking interstitial spaces across divided and fragmented cities, repositioning urban gaps as constitutive relational formations rather than residual spaces.