Nowadays it is well known that the in-depth process of knowledge plays a key role in the field of cultural heritage. This knowledge should objectively allow identifying both the several structural elements and their mutual connections, both the quality and the state of damage of the materials characterising the case study. The final goal is the evaluation of the safety level of historical constructions. In some cases, the lack of documentation or, in some other cases, the incompleteness of the information provided by the existing documents, until the discrepancy between the design and the real construction, lead to obtain information by means of the direct analysis of the building. The structural survey, hence, which belongs to the broader topic of the structural diagnostics, becomes a tool that allows interpreting geometries and damages. A tool able to adapt to the several peculiarities of historical constructions and to address the investigation techniques to the specific problems. In this way, it is possible to define the state of damage, its causes, the safety level and to the select the most appropriate strengthening techniques to repair and improve the building structural behaviour. The comparative analysis of some case studies allows highlighting a wide range of situations that forces to consider each building as a unicum (although recurring constructive typologies are present). To this aim, specific investigation techniques and processes are required as well as an interdisciplinary approach, with the involvement of expertise coming from several fields. Contrary to what was believed in the past, safety and conservation are not antithetic concepts, but it is possible to guarantee a harmonic union between them by means of the structural survey as well
