Has the increase in social life and conviviality commonly imagined by the designers and decision-makers taken place? There are few systematic post-project evaluations of the methods and tools used to answer this question. Therefore, this article wishes to draw lessons from a housing experiment from the end of the 1970s, the Grand’Goule residence in Poitiers, the objective of which was to create a dense social life through design and means of participation. Some devices consisted in the creation of Surfaces d’Activités Partagées (SAPs, shared activities surfaces), which are common spaces where residents can intervene in both the interior design and the function of space itself. In this study, we analyze the Grand’Goule project, which has been displayed as a participative experiment, with the objective of creating a dense social life through original architectural and social devices. We use different sources (interviews of the inhabitants, project owners, and architects, alongside press articles and the architects’ archives) to dissect the practices in order to lead a retrospective analysis of the participative process, its successes and failures. We show that, as a very complex and fragile process, enabling the active participation of people in the design and use of a large-scale architectural project is far from obvious and suffers from several kinds of difficulties. We highlight the gap between initial intentions, final realizations and actual uses in the Grand’Goule project, and how it can inform every participative architectural project.