## 6 Discussion and Conclusions  
Based on the authors' experiences, restoration work on historic stone buildings is often carried out without a dedicated, preliminary diagnostic stage. In fact, diagnosis is often not explicated (i.e., a rapid evaluation is conducted simultaneously to the restoration) and, when it is, it may rely on empirical and subjective evaluations (color changes, different sounds as results from \"knocking\" the stone). Regardless of the skills of the operators, who might deliver state-of-the-art results, such an approach has several limitations. First of all, the lack of a clearly defined diagnostic project and, therefore, of a list of repeatable tests, and/or the adoption of qualitative and empirical evaluations, make it difficult if not impossible to monitor the state of degradation with time. For example, a 10-year restoration program would have to face issues related to comparing the results obtained by different people and, likely, different methods, not to mention the increased probability of human  
Figure 12: (**A**) Backscattered electrons (BSE) SEM with an overlapped porosity mask highlighting the preferential pore concentration along laminations (dashed lines). (**B**) Enlarged view of the lamination (white rectangle in **A**) showing the textural relationships of primary phyllosilicates and secondary clay minerals with respect to elastic particles and carbonate cement. Bt = ibotite; Mu= muscovite; Cc = calcite; Do = dolomite. error related to experience-based methods. Second, difficulties would also arise when comparing two different buildings or two different facades of the same building, which would be useful to assess the effects of weathering and restorations. In other cases, quantitative analyses are indeed performed but they mostly focus on the chemical and petrographic sides. While these are an important part of a diagnostic project, some important rock mechanical characteristics can be overlooked, like the role and conditions of the discontinuities and properties of a rock beneath the first cm from its surface, features that are prominent in determining the ultimate stability of stone elements. Therefore, the purpose of this paper is to propose an all-around diagnostic protocol encompassing some of the most advanced methods in a multidisciplinary approach. The aim is to provide a complete characterization of stone materials and their state of conservation, allowing us to manage multi-scale surveys through a specific investigation protocol. Such a protocol is intended for heritage operators, restorers, researchers, local administrations, and building managers, who are pointed toward a number of quantitative, repeatable tests that can be done, together with indications on how these and the qualitative analyses can be carried out. However, since there is no such thing as an ultimate diagnostic project that is suitable for every stone building, every step of the presented protocol is thought to be customized, removed, or replaced as needed. In particular, the proposed multidisciplinary methodology for the technological knowledge, characterization, and diagnostics of built cultural heritage was applied to historic Florentine buildings characterized by stone facades. The diagnostic project workflow first involved the historical analysis and the architectural survey, then a complete characterization of the rough-hewed rusculated blocks was carried out through decay and optometric surveys, and mechanical, physical, mineralogical, and petrographic analyses. The on-site mechanical investigation was performed through NDT, specifically using ultrasonic pulse velocity and sclerometric measurements. In parallel, a few destructive tests (DT) were carried out to characterize the stone material through physical properties and petrographic and mineralogical features. In addition, to optimize the data integration, a data management and analysis system has been set up.