Models of urban development and growth are increasily predatory on nature and wasteful in utilization of ressources. Traditional dwelling schemes are not suitable anymore for new patterns of family life in highly populated cities. Besides, cost of housing is becoming unaffordable for large segments of population who are forced to pass their lives in unlivable small spaces. Living Big addresses this major issues with a design proposal that bases on a system of transformable furniture units that allows the creation of flexible compact houses. This system, applied to constrained spaces, gets the most of living spaces with limited ressources allowing good living conditions for its inhabitants. Living big has been successfully applied to a very poorly constructed house in Madrid city center with unhealthy living conditions (poor lighting and ventilation, extremely compact space...) and it is settled as a system that provides solution to a large number of degradated housing units in cities.