The evaluation of the masonry quality in historical load-bearing stonework

Historical buildings may have different types of wall texture, often as a result of their function. In fact, depending on the function for which they were built, particular types of masonry were realized with a construction technique appropriate for each kind of purpose: defensive architecture, religious buildings, residential buildings, rural buildings, etc. Some buildings have been designed and built to last for centuries and, therefore, the load-bearing structures have been carefully constructed with the best knowledge of that age and that particular geographical location, using traditional materials locally available. For this reason, the stone masonry walls of historic buildings often show a great variety, not only in terms of materials but, above all, of constructive technique. The study of the morphology of a load-bearing masonry wall is fundamental for the evaluation of its mechanical behaviour under different actions. Characterization only of the individual components (stones and bedding mortar) is not sufficient. Therefore, understanding the construction technique and assessing its quality is essential for evaluating structural safety, especially if the construction is located in a seismic-prone area. The paper presents a complete and systematic method for the quality assessment of stone masonry. The method is based firstly on a visual inspection and then on non-destructive or slightly destructive investigation techniques. This systematic approach allows to compare different stone walls surveyed in different buildings in the same area, in order to recognise the characteristics of the local “rule of art”, according to geographical conditions and recurring risks.