The laboratory analyses (x-ray diffraction, mercury porosimetry, scanning electron microscopy with energy dispersive spectrometry, etc. ) and climate measurements (temperature, relative humidity, atmospheric pollutants) taken in the span of a whole year have allowed the identification of the processes of stone deterioration. Candoglia marble is decayed by a chemical process superficial solution by rill washing waters. The Carrara marble is decayed by both chemical and physical processes with gypsum crusts formation and intergranular decohesion. The Simona sandstone is decayed first by a chemical process and second by a physical process with scaling and flaking caused by frost action.