"The study of urban wastelands as specific forms of interstices engages researchers to intersect disciplines, knowledge and positionings on the border between ecological and social dynamics. The Interfriches network - carried by an interdisciplinary collective - was created in 2019 to bring together human, social and environmental scientists and practitioners on the common object of urban wastelands. Involving architects, geographers, urban planners, ecologists, sociologists, politicians, artists, it seeks to reflect on the role of wastelands in the making of the city in different contexts. Based on a workshop on a third place (i.e. a place of social bonding, emancipation and collective initiatives) in the suburban Paris, this paper puts collective methodological questioning into dialogue. What does an interdisciplinary workshop including collective surveys allow to capture about an occupied urban wasteland? We aim to make a reflexive analysis of the frameworks and limits of this commoning experience."