Mass customization is being adopted in many housing contexts worldwide to provide families with dwellings that suit their individual needs at costs similar to the mass produced. However, in many social housing contexts there are barriers which can hinder the adoption of mass customization despite the benefits it could bring to residents. This is the case in the Brazilian social housing context considering house units for the lowest income range of housing programmes. This paper explores the possibilities and limitations of applying mass customization in this context to improve the living conditions in these neighbourhoods as they evolve over time. We analyze the ecology of the system of provision of social housing for the lowest income range, pre-occupancy and in the neighbourhood's development over time. We propose that applying a mass customization strategy post-occupancy in this context has a higher potential for bringing significant benefits over time not only for the families, but also to the city and other stakeholders. This study shows some directions for such post-occupancy mass customization approach.