The historic monuments from the viceregal period in the south of Peru are the great part of the historic centers in the most important cities. They were mostly built with “sándwich” walls. They are built with volcanic stones which are parallelepiped in shape, and an intermediate sand and cal filling. During seismic waves these walls have shown the highest vulnerability. The main objective of this study is to know the behavior of unreinforced and reinforced masonry walls with concrete confinement, under the monotonic lateral test comparing them by increasing the capacity of resistance and the deformation of the reinforced walls. The experimental tests consisted in to try out three walls on the scale of 1/10, each with a different precompression load; these were tested at 0.5% drift, corresponding to a moderate earthquake. After this test, the reinforced concrete confinement frame was inserted, and the 3 samples were retested until they collapse. The 3 walls were tested under lateral load without reinforcement, there was a failure due to the flexion at the base by a drift of 0.04% and it lost stability. The reinforced wall increased its capacity of resistance and deformation, it shows an adequate ductility for severe earthquakes, being the drift got for the failure by flexion at 0.06% and a drift for a failure by cut at 0.8%.