Durability and degradation of natural stone in Syracusan façades: materials and techniques compatible for the recovery

The building heritage on the island of Ortigia, the historical center of Syracuse, is characterized by the texture and color of the local calcareous stone. Natural decay and alterations, due to human action, constantly modify the image of the city perceived by the users. In fact, the chemical and physical characteristics of the stone typical of eastern Sicily allows a quick and intense degradation of the façades due to various environmental factors. These effects are stronger in buildings with defects resulting from design flaws, from construction techniques or from ineffective recovery interventions. The aim of the study is to deepen the knowledge of the natural stone of Syracuse, used both as a structural component and in decoration of the façades, in order to identify methods of intervention and design solutions that are compatible with this particular kind of stone. The analysis of the chemical and physical characteristics, in relation with the surfaces' treatment, will be compared with the intensity and the rapidity of degradation evolution. In addition, a survey of the alterations due to recurring defects of the construction will be performed, verifying the success of restoration interventions carried out on the façades in Ortigia through the study of the employed techniques and the results obtained. The research will define guidelines for the strategy of recovery interventions, in order to improve the performances of Sicilian stone and to increase its durability.