The aim of the research-by-design project The Hackable City is to develop a research agenda and toolkit that explores the role of digital media technologies for new directions for urban planning and city-making. How can citizens, design professionals, local government institutions and others creatively use digital technologies in collaborative processes of urban planning and management? The project seeks to connect developments of, on the one hand, city municipalities that develop smart-city policies and testing these in ‘urban living labs’ and, on the other hand, networked smart-citizen initiatives of people innovating and shaping their own living environments. In this contribution we look at how self-builders in urban lab Buiksloterham in Amsterdam have become ‘hackers’ of their own city, cleverly shaping the future development of a brownfield neighbourhood in Amsterdam’s northern quarter.