Intervention strategies were performed in many engineering applications. In particular, for brittle materials (e.g. masonry) the strengthening strategy must be performed improving also the ductility capacity. However, many of the available models both in the literature and in the building codes are not able to accurately account for the behaviour of strengthening systems on the capacity of strengthened elements. In particular, they provide reliable results for composite based on organic matrix (i.e. resin). For these strengthening systems, matrix contribution can be neglected. For strengthening systems based on inorganic matrix (i.e. cementitious or lime-mortar) the stiffness and strength of the matrix provides non-negligible effects on the ultimate behaviour of strengthened elements.