Hydrogeological control on the moistening and degradation state of walls: general implications of the Ferrara (Italy)

The humidity level of walls is controlled by both the porosity-capillarity property of the structure and the hydro-geological nature of the bodies underlying the building foundation. A geological interpretation of the substratum would be therefore needed for a proper genetic understanding of the building condition to be achieved. The brick formed historic town of Ferrara developed during Medieval times along the Po River natural levee sedimentary body and then expanded onto both river sand and flooding plain argillaceous units. A strong linkage therefore connects the sedimentary evolution, the urban growth and the present-day moister and degradation level of historic buildings. The high permeabily sand area are characterized by elevated levels of humidity and salt precipitation, whereas the low permeability clay zones show comparatively reduced moisture rising. The historic gutter framework also plays a major role in controlling the humidity distribution in building.