Masonry often requires strengthening to withstand against extreme actions such as earthquakes, cyclones and flooding. Recently, new methods have been developed to strengthen masonry, such as fabric reinforced cementitious matrixes and fibre reinforced polymers. However, other strengthening systems such as welded wire meshing (WWM), reticulatus and plastering with cementitious matrixes/mortar (CP) have been also practiced to reinforce masonry, conversely no systematic design guidelines are available for these methods. In this study, an attempt has been made to establish rational design approaches to predict the shear resistance of WWM, reticulatus and CP methods. Three sets of experimental database have been developed for design verification. The effectiveness of these strengthening methods was appraised by comparing their structural performances. The available formulations to predict the shear resistance of unreinforced masonry (URM) and CP strengthened masonry were assessed against the established database, and suitable modifications were proposed to effectively account the contribution of cementitious matrix. A unified approach to estimate the shear strength was proposed based on the contribution of URM, CP and reinforcements. The design approach is shown to conservatively predict the shear strength of strengthened masonry.