The extent to which certain kinds of people are inundated with toxins, pollutants, bacteria, viruses, violence, and disaster is well documented. The various ways in which the extension of urbanization as a planetary phenomenon has refigured geographies of sustenance is also well established. This article focuses, instead, on exploring the interfacial oscillations among that which is experienced as habitable or uninhabitable, as a kind of regionalizing of relationships between life and nonlife. It looks at how possibilities of living disappear and reappear, often in the least expected situations and circumstances, and at how inhabitation itself becomes increasingly precarious through various devices and calculations deployed in order to guarantee it. Drawing upon decades of research and program development in urban Africa and Southeast Asia, the article explores some of ways in which the habitable and uninhabitable are redescribed in terms of each other and considers how this redescription could be used to formulate more judicious modalities of viable urban development, as urbanization itself seems to posit increased dangers to the viability of many lives.