Le torri costiere della Sardegna nel Mediterraneo: cronotipologie delle strutture murarie

The research focuses on the system of coastal towers in Sardinia, the realization of which spans more than five centuries (XIII-XVIII sec.) and reaches its peak between the sixteenth century and the first half of the seventeenth under the impulse of the Spanish monarchy. The coastal fortification process seems well documented in archival sources thanks to the establishment, starting in 1583, of the Reale Amministrazione delle torri This institution managed the system and produced a copious technical and administrative documentation. This made possible the philological dating of construction phase and historic restorations works referring to several towers. From this awareness comes the desire to investigate, in reference to these buildings, the structural and material characteristics, with particular emphasis on building techniques with the aim of defining an abacus with chrono-typological value. The choice of subject was also influenced by the awareness of the absence of studies, referring to Sardinia, oriented to the knowledge, documentation and chronological definition of construction praxis adopted for the construction of the masonry structures. So, with the awareness of the influence that Spain exercises in the definition of the architectural types and construction techniques in the countries that were under his dominion (direct or indirect), the ongoing study opened to the comparison between Sardinia and other Mediterranean contexts. Considering the high number of buildings investigated, the study was structured in homogeneous districts also taking care to safeguard all-embracing perspective that takes into account the specificity of the system. Starting from a systematic investigation in situ, eight representative cases-study were identified, selected from the towers belonging to a precise chronological range (16th-17th centuries). Specifically, the study focused on the following towers: Porto Giunco (Villasimius-Sarrabus Area), Mezza Spiaggia (Cagliari Area), San Macario (Teulada-Chia Area), Capo San Marco (Oristano Area), Ischia Ruggia (Bosa Area), Airadu (Alghero Area ), Trabuccato (Stintino-Asinara Area ) and Isola Rossa (Gallura Area). The need to ensure a systemic approach to the subject, and then to detect a large number of buildings, determined the decision to integrate the classic relief tools with innovative survey methodologies, based on photogrammetric techniques. This made it possible to acquire, in a short time, a satisfactory number of data related to the volumetric characteristics of the investigated buildings, allowing you to check and sometimes refute the previous typological classifications. At the same time, the processing of the product derived from "photomodeling" process provided a detailed basis on which to conduct analytical studies. With the objective to evaluate the many aspects of the subject, a multidisciplinary and integrated protocol was adopted: the towers were studied from a historical point of view, architectural and typological, technical and mineral-petrographic favoring a stratigraphic approach tailored to the peculiarities of the topic. Cataloging, georeferencing and insertion into a geographic information system made it possible to establish a multi-layer dynamic comparison and thus to reach a critical synthesis of the results obtained. This methodological approach has led to interesting results and represents a small advancement in the knowledge of these artifacts. In general, while taking into account the number of persons who commissioned the construction, all the towers analyzed shared the choice of a type of easy to build, with technical and architectural solutions far from modernity that characterized other similar systems. The adoption of these solutions, however, meets the basic military requirements. It is strongly influenced by the scarcity of population and economic resources and the need for shorter construction times. Indeed, a low population density in the island coasts and the constant shortage of financial resources, always aggravated by lack of interest by the central government, justified the adoption of a particularly expensive model. Similarly, in the realization of masonry structures, the short construction times and lower construction costs represent common imperatives. These aspects have influenced the quality of the mortar, often not optimal, and the choice of the stone material. Also the masonry technique most commonly adopted, a cantieri, was an expression of the same needs. It used the most of the available materials, responding to structural requirements. The systematization of the dimensional data relating to the cantieri revealed the recurrence of certain values such as to identify invariants of great interest for the chronological definition of masonry structures. The texture appears almost always irregular, with extreme heterogeneity in dimensions and morfhology of the stone elements. It was conditioned, as expected, by the level of workability of the material. The data obtained in the analytical phase converge in the project guidelines, aimed at providing methodological ideas and cultural references useful for restoration works. In addition, the multidisciplinary approach, supported by the integration of technological and innovative technical tools, reveals a spendable methodology in other contexts, and to a larger scale. Finally, the typological classification of a wide repertoire of masonry techniques, referred to a specific chronology can be an important basis of comparison for the dating of contemporary buildings.