The success of the preliminary studies phase is calculated on the basis of its capacity to describe all aspects that make up the building and the characteristics of its mechanisms of alteration. The approach to the materiality of the building starts from a vision of its general nature and proceeds to the details of its form and structure, as the final goal is to achieve a complete descriptive model of the architectural organism and its immediate surroundings. The preliminary study phase sets out a procedure of decomposition and recomposition of the building, based on a metrical survey inspired by the criterion of exactitude, and on a historical study that takes into account both the synchronic as well as the diachronic nature of the building’s transformation over time. The aim is to arrive at a justified diagnosis of the state of conservation of the architecture in all its specific aspects, so that with regard to all verified problems, the origin, evolution and effects on its present state are known.