Latham and Layton refine social infrastructure by distinguishing several meanings that had begun to travel under the same term: people as infrastructure, the social relations surrounding hard infrastructures, infrastructures of social care, and the public or quasi-public places that support social connection. The paper’s iconic move is conceptual disaggregation. Rather than treating social infrastructure as an intuitively positive label for any socially useful place, it asks what kind of infrastructural work is actually being described. Its theoretical contribution lies in returning infrastructure to capacity: infrastructures facilitate, support, service and sustain activity, but they do so through different material, institutional and political arrangements. Methodologically, the text urges urban researchers to specify the infrastructural object, its users, its relations of access and its mode of support instead of relying on broad metaphor. This creates a bridge to critical urban geography, where infrastructure is simultaneously material provision, unevenly distributed capacity and political form. The concept becomes strongest when its empirical register is made explicit.