This paper presents an experimental study aimed at the characterization of the mechanical behaviour of existing masonry. The research proposes a methodology based on the in-situ core drilling of existing masonry members, made of clay brick and low-strength lime mortar. The obtained cylindrical samples, with different diameters, are tested in the laboratory to derive the compression and frictional response of the composite material and the components (units, mortar). The paper addresses the main issues related to the extraction of cylindrical specimens, the testing and the interpretation of results. The proposed minor destructive technique is suitable for existing masonry structures and especially for those of the built cultural heritage, since a direct estimation of the mechanical parameters can be obtained without damaging excessively the historical structure.