Assessing the mechanical properties of irregular stone masonry in historic buildings is a challenging task, as it is highly heterogeneous with many uncertainties involved. In-situ Non-Destructive (NDT) or Minor Destructive (MDT) testing can be implemented to evaluate the mechanical properties; however, this is often difficult due to restrictions by legislation, policy and guideline that protects the heritage of listed buildings. To comprehend the mechanical properties of stone masonry, an experimental database comprising the mechanical properties of stone masonry determined through axial compression, double flat-jack and diagonal compression tests was established and analysed in this study. The stone masonry assemblages in the database were categorised using the Italian building code and Masonry Quality Index (MQI) method. The experimental database includes compressive and shear strengths, Young’s and shear moduli of different stone masonry types before and after reinforcement. The mechanical properties were appraised to verify their correlations among them, and to assess the effectiveness of both traditional (grout injections, steel mesh cement coating, etc.) and innovative (Reticulatus technique and composite materials) retrofitting methods. The database and analyses presented in this study would enable to further understand the mechanical properties of traditional stone masonry and select appropriate strengthening techniques.