Existing policies in Europe and in the Belgian region of Flanders have set ambitious targets for future-proofing cities: promoting the climactic renovation of existing houses, the adaptation of urban spaces, and the transition to circular material use. However, at the current pace of development, it appears unlikely that targets for operational and embodied energy performance can be achieved. Policies tend to focus on the individual homeowner as the agent of change, and most technical scholarship focuses on the performance of singular houses—overlooking the potential gains to be made from a collective approach to urban adaptation. This paper will introduce strategies for collective and circular urban transformation, through several case studies which are part of the Flemish VLAIO-funded “impaC3t” project. The project brings together diverse stakeholders and experts to broaden and deepen existing renovation strategies, focusing on several levers for acceleration. One lever is social housing companies as early adopters of circular innovations: with a relatively large amount of housing stock which must be renovated in the coming years, social housing providers in Flanders function at a scale where solutions such as prefabricated renovation and circular material banks become feasible. Another lever is in extending the renovation plans of social housing estates to neighbouring homeowners: inviting and encouraging the private market to take part in this collective effort. And a third lever is in building upon existing momentum: linking individual renovations to larger collective schemes such as sustainable energy networks. This research discusses the barriers and opportunities in collective circular transitions as observed in ongoing case studies.