This project introduces the concept of collateral space to describe how housing is conceived not only as homes but also as assets backing debt. It redefines residential landscapes by showing how large-scale mortgage schemes shaped architectural forms, layouts, and urban expansion. Focusing on Amsterdam’s postwar expansion neighbourhoods, the project links building permits with mortgage registrations in a digital database, enabling systematic analysis of which spatial elements were registered as collateral. By tracing how financial logics co-produced space, the project highlights the historical roots of asset-based housing, revealing connections between postwar planning, mortgage finance, and the long-term reproduction of housing inequalities.