From tradition to innovation: Plaster at risk under severe climatic conditions

The research identifies strategies to increase the durability of the components of historic buildings and minimize the environmental impacts. The method has a direct application within the Conservation Plan of Lavello Convent (Lake Como). The study case is particularly representative of the historical building techniques and materials in the Northern Lombardy region. The study case presented the highest risks for the conservation of traditional finishing on site, because of the adverse climate and the particular exposure to rainfall of the exterior north facing plaster. The researchers studied six mortar mixes to identify the durability and compatibility compared to the masonry underneath, for repairing/substituting the exterior plaster of the northern side, which faced the worst conditions. The same formulations were tested on the specimens in the laboratory too. The diagnostics focused on the characterization and assessment of the water transport phenomena in mortars, through different tests, studying the absorption and vapour transmission properties by means of steady and innovative non-destructive techniques. A second step of the research included the application of protective products on the specimens, and on biocide and protective products on the site and the repetition of the tests. At the end of the experimental tests, the results were implemented in the ongoing Conservation Plan and especially supported the decision process for defining the threshold between maintenance and acceptable damage, and, consequently set the inspection procedures, cycles of maintenance of protective/biocide treatments, and the economic plan.