In this paper the mechanical behavior of a masonry wall is studied. The masonry is regarded as a composite realized by a regular arrangement of blocks into a matrix of mortar. Hence, a panel of masonry is a three-dimensional heterogeneous body with a finite thickness and R2-periodicity in the plane of the wall. A micromechanical approach is proposed to get the overall properties of the masonry. Then, a case of a wall reinforced by FRP-layered sheets placed on the surfaces of the wall is analyzed. To model the overall behavior of the unreinforced and reinforced masonry, by accounting for the progressive damage of the mortar, of the block and of the FRP sheets, a simple homogenization technique is proposed. Two different damage criteria are adopted for the mortar and the block, within isotropic viscoelastic and elastic damage models. Furthermore, a brittle damage model is used for the reinforcement. Finally, numerical applications are developed by adopting the proposed procedure in order to investigate on the damage of the unreinforced and reinforced masonry panels.