Systematic and thorough investigation of building structures is a problem of primary importance before restoration. In fact, the planning of any intervention is unconceivable without a proper insight into the original project and the successive phases of transformation of the building. Experimental survey and historical research have been employed so far as aids to this understanding; nowadays thermographic technology allows to obtain important data and information on wall structures by means of a non-destructive method. The study carried out on Palazzo Fossombroni has demonstrated that this method will always be fundamental for restoration projects of buildings.