Human habitations often last longer than their inhabitants. What is to become of old buildings in the long term? This is the question this article seeks to address based on an ethnographic and historical study of a Haussmanian building in Paris. The study leads to an examination of several key issues: the material and financial aspects of the maintenance and the transformation of the building, the social and demographic range of households who either own or rent apartments, the part played by the real estate and building maintenance professionals, and the legal and political context.