Geometry and Construction Techniques of Late-Baroque Domes in Central-Eastern Sicily

A detailed knowledge of a historical building is an indispensable requirement for its conservation, either for addressing strategic choices, or for defining the most appro-priate restoration project. In this context, this study analyses some exemplary domes, built between the XVIII and XIX centuries in the central-eastern area of Sicily de-stroyed by the strong 1693 earthquake and known as Val di Noto. Post-seismic reconstruction of ecclesiastical complexes was often enriched by soar-ing domes, with the aim of witnessing the importance of the religious order. The complex construction of these structures, sometimes subject to collapses, was based on empirical rules, derived from the study of famous examples and from the analysis of historical treatises. The present study, basing on archival documents and high precision 3d surveys, analyse the design rules, the building techniques, and the local influences leading to the construction of six domes. These domes, nearly intact in spite of the numerous seismic events occurring throughout the centuries, are located in Catania, Piazza Armerina and Caltagirone. In particular, the research concerns the rules, written or arising from common prac-tice, of shape design and construction of such daring structures. Past design meth-ods, in fact, were based more on proportional criteria rather than analytical ones, i.e. drawn by construction science; furthermore, architects engaged with domes, in addi-tion to suggest operational hints on materials and methods, often searched for the ideal shape with the best balance between stability and beauty. In this respect, Carlo Fontana, author of the 1694 treatise Templum Vaticanum et ipsius origo, attempted to derive a general shape of domes from the analysis of Michelangelo’s S. Pietro Ba-silica in Vatican City. The investigation on the six domes included also the study of their construction tech-niques, indicating the tight connection with local masters and materials. The analysis of archival documents and of survey data allowed us to attempt to derive the project shape of each dome by the geometric construction and to establish, by comparison, the connections between design and construction, and the possible links between the different projects, as well as those between projects and historical treatises.