One of the main difficulties when working with heritage structures is the difficulty of assessing the compressive strength of masonry and the other mechanical properties such as the elastic orthotropic properties. In addition, actual masonry codes are focused on modern fabrics which normally include Portland cement mortars. In fact, such mortars are very different from the ancient ones, mainly based on aerial lime and sometimes hydraulic lime. Then, in spite of knowing the properties of the bricks and mortar of existing structures, architects and engineers are not able to obtain a good estimation of the masonry mechanical properties because the values are below the range included in the codes. In addition, obtaining mechanical properties from a full masonry specimen is much more difficult than obtaining the characterization of the individual components. The main objective of this Master Thesis is to obtain simplified expressions, similar to those provided in standards such the Eurocode, to produce good estimations of the mechanical properties of heritage masonry which include low strength mortars. To this purpose, it is proposed to use systematically a numerical tool, based on analytical expressions, able to compute the composite material properties of masonry from those of the components, to produce a vast collection of results varying different parameters such as the components' strength, young modulus, joint and brick sizes, etc. With this database of results, validated with some existing experiments, simple closed form expression will be adjusted to produce good estimators of these properties to the practitioners.