In contemporary western society, family patterns are undergoing considerable transformations: new housing courses for young people, migratory flows, the formation of one-parent families and the increasing number of people living alone ensure that the traditional family is no longer the dominant social unit, with the consequent need to diversify the housing offer. Moreover, if we consider that in 2030 two thirds of the world's population will live in the main urban areas and that the population over 65 years old will represent more than 25% of the total, it is at least necessary to consider housing density and functional complexity as fundamental features in modern collective housing. In order to meet modern residential needs, the Patronat Municipal de l'Habitatge de Barcelona (PMHB), main administrator of the Catalan city's housing clusters, has launched a process of the public offer's diversification by building high-standard architectural housing models specific for the most vulnerable categories of society. The book introduces the most significant 10 collective residential projects, realised by the PMHB in the last years. These projects allowed the PMHB to strengthen its position among the most representative European entities experimenting and innovating to meet the communities' needs. Text in English and Italian.