The recent growth of cooperative housing in Spain questions existing design standards and regulations as well as cultural norms of ownership, management and current housing typologies. This paper analyzes the design opportunities and challenges emerging from this. It studies the transformative capacity of housing cooperatives and how the realization of new social, spatial and economic demands is restricted by regulatory and administrative frameworks that limit collective ownership and use. Based on a case study analysis of recent projects in Barcelona, the paper discusses how regulations condition housing design, but also why changing ideas of ownership, household and dwelling structures require a review of how regulations are formulated and implemented. It examines this in the context of designing with housing cooperatives and their ethos defined by engagement in and responsibility for all decision-making processes and self-management. In cooperative housing, architecture is a process, not a product, one that extends beyond the completion of a building. This gives credibility to the claim of cooperative housing not just as a grassroots response to housing failures, but also as a political project of democratization and social transformation.