Buildings are demolished when they are considered obsolete, in other words, when they have reached the end of their lifespan. Demolition leads to waste; in Europe, construction and demolition waste accounts for approximately 25-30% of the total waste generated, and rubble produced during the construction and demolition of buildings accounts for 12% of total waste in Europe. In the face of climate change, there is a need for rethinking the management of resources. Circular economy advocates for lengthening the lifespan of products, infrastructure and buildings in order to reduce the creation of waste and associated environmental impacts. However, determining the lifespan of a building is not self-evident, it extends far beyond the material’s lifetime, into factors such as economic utility, functionality, cultural significance, sentimental value and political weight. Circular economy research can benefit from a deeper discussion of what constitutes the ‘end of life’ for complex objects such as buildings, and in particular residential buildings. With cities racing to address their housing crises, there is an urgency to understand how dwellings can meet their inhabitants’ needs for as long as possible, and what finally leads to the obsolescence. Therefore, I propose the question: When does a dwelling reach the end of its life? I will present theory on the topic of ‘obsolescence’ in buildings, as a diving board for the discussion. My objective during Doc.days is to find others who are knowledgeable or interested in the topic of circular economy for the build environment, or the topic of housing in Geneva. Both would contribute directly to my PhD research.