The Caja de Agua development was initially proposed by the Peruvian state housing agency in 1961, as part of its programme to create a new kind of housing project: the Urbanización Popular de Interés Social (UPIS, or Low-Income Social Housing Subdivision). The UPIS offered organized urban development to a minimum standard, substantially below previous government-sponsored housing projects, in an effort to accommodate low-income residents. The urban layouts were to be prepared by the state housing agency, with a range of basic services, and the residents committed to purchasing a core house that they were expected to complete over time using self-help labour. The design of the dwellings followed the concept of the casa que crece (growing house), first proposed in Peru by architect Santiago Agurto in his entry to a 1954 housing competition, and subsequently implemented on a trial basis in a state-sponsored project at Ciudad de Dios, Lima, in 1957. Such projects borrowed and systematized the techniques of barriada (squatter settlement) housing – progressive development, resident participation in construction – but aimed to circumvent ad hoc building through technical assistance and carefully conceived expansion plans . . .