Conservation of heritage buildings still poses many challenges. Throughout the history, monuments have been exposed to catastrophic earthquakes. Assessment and retrofitting of this architectural heritage are effective measures to prevent their destruction by future earthquakes. These operations require good knowledge of the mechanical properties of the material because is one of the most important steps for a suitable seismic assessment. Mechanical characteristics may be determined through destructive, semi-destructive destructive and non-destructive tests. As the application of destructive and semi-destructive testing on heritage buildings is often impossible, many attempts have been made to propose fully non-destructive methods for determining mechanical properties. One of the methods is called the Masonry Quality Index (MQI), only based on visual inspection. This method aims to develop a simple and systematic approach to the analysis of masonry constructions based on idealized typologies, different parameters and the mechanical properties of the constitutive materials (stone, brick, mortar, etc.). The aim of the present research is to propose a simplified approach to obtain mechanical properties of the historical masonry walls with lime mortar in Campania, by correlating the MQI, double flat jack and further non-destructive test results.