This paper explores the role of social impact assessment (SIA) as a tool to evaluate the social sustainability of council estate redevelopment or regeneration. The paper first revises the evolution of the concept of SIA in recent years, arguing that it should be included as a core part of the planning approval process to enhance community-centred planning decision-making practices, as claimed by the Just Space network in London. To contribute to this argument, the paper explores how to co-produce an SIA with those communities that are potentially affected by the scheme. We use as a case study William Dunbar and William Saville houses, two housing blocks located in South Kilburn Estate, London Borough of Brent, which are planned to be demolished as part of a large estate redevelopment scheme. The paper uses a diversity of participatory action research methods to co-produce an SIA with residents from the two housing blocks. From the experience of co-producing an SIA with residents, the paper comes out with three sets of findings and contributions. Firstly, the paper provides findings on the impact that demolishing the homes and re-housing residents would have on residents. Secondly, from these findings, the paper contributes to the argument that SIA should be incorporated into the planning system, but they should be co-produced with residents and carefully applied rather than becoming another box-ticking exercise. Thirdly, the paper provides very relevant methodological contributions on how to co-produce the SIA with those potentially affected.