Addizioni, integrazioni, innesti : la costruzione metallica nella conservazione e nel riuso delle architetture storiche.

«If necessary, for a proper use of the building, completion of more extensive spatial and functional parts should reflect contemporary architecture». The statement taken from the Krakow Charter (2000) clearly defines the characters of the interventions made by the use of metal structures or devices in the restoration and the reuse of historic buildings. At the turn of the Twentieth and Twenty-First Century, the restoration interventions carried out by these techniques interpret the theme of the addition, or the filling of the lacuna, as a design opportunity in which the steel becomes an instrument of the architectural syntax. The use of building materials such as steel, corten and titanium allow the development of additions/integrations that arise as new stratigraphic layer of the historical building. These elements/structures aspire both to the highest reversibility and to a clear syntactic and formal distinction from the past, helping to minimize both the impact and the extension of the interface between the pre-existences and the new integrations. As the paper will highlight, starting from the second post-war period, many interventions carried out by these techniques in historical contexts are characterized by clear formal similarities. Nevertheless, the meanings and the architectural language of the integrations should be considered in terms of the inner coherence of the design choices, with particular attention to define the details that compose them. In fact, the working draft of the intervention and in particular the anchorage techniques used to connect historical masonries with new insertions allow to underline significant differences in the conservation of the built heritage.