The present paper has the purpose to compare the shear strength obtained using the values proposed by the code for a level of knowledge LC3 [1,2] of a masonry structure with those experimentally obtained from the mechanical tests with flat jacks and the compression tests on stone elements. The shear strength criterion of Mohr-Coulomb has been utilized, applying for the cohesion and friction angle the values obtained by the non-linear criterion of Hoek-Brown for rock masses [3]. For the last criterion an analogy has been assumed between rock mass and masonry; it has been properly adapted to the specific case of masonry structure examined in the paper.