In the present study the possible chemical interactions among the constituents of historical walls have been investigated. In Venice but also in the whole mediterranean area the “cocciopesto” (constituted of powder and brick fragments which traditionally confer hydraulic properties to the mortar) has been widely employed both for mortars and the so called “marmorino” plasters. The work has been developed by examing the brick-mortar interaction on historical buildings in Venice. The samples were chemically analysed through XPS and XPSImaging techniques in order to ascertain the chemical composition of the interface layers. The results clearly indicate that a true chemico-physical interaction between brick and lime is present in the historical materials. A calcium carbonate accumulation has been observed at the brickmortar interface.