Symbiotic Architecture for building and urban rehabilitation

Processes of increase in urban population have always been characterized by an alternation of phases in which densification of existing urban fabric prevailed, with other in which the prevalent phenomenon was urban expansion. Phases of density increase are related to physical constraints or economic-political issues. Expansion prevails in periods in which constraints disappear. In recent decades, the housing bubble has fostered the so-called urban sprawl, which irreversibly subtracts room for agriculture and natural environment. The goal of sustainability imposes to hold down land consumption. Nevertheless, evolution of needs and changes in activities require adequate spaces. This paper proposes the use of symbiotic architecture to requalify and rationally densify urban fabric: the possibility to create new built volumes in already-urbanized areas prevents the creation of new infrastructure, allowing to allocate resources to the redevelopment of existing ones; the increase of building density consent neighbourhoods to reach a critical mass of inhabitants allowing the establishment of new services. Proposed solutions cannot be regulated by general rules; they should be governed by specific urban plans based on the study of the anthropic load on existing infrastructures and on the protection of already saturated areas from property speculation.