"È questa un'opera d'arte che non doveva essere toccata": addenda su crollo e ricostruzione del Salone Sistino nella Biblioteca Apostolica Vaticana (1931-1933)

On 22 December 1931, the dramatic collapse of the Vatican Library’s middle section led to the devastating loss of six people, 15,000 volumes and part of the structures and decorations of the building constructed in 1587-1598 by Domenico Fontana for Pope Sixtus V Peretti. As early as 1928, the Vatican Library had undergone decisive functional adaptations works, first in the so-called Arm of Julius II, but later also in the Sixtine building. These measures were made necessary by the introduction of heavy cast-iron bookshelves, as well as by the opening of large arches on the external facades and in the spine wall of the Library. While the chronicle of the terrible collapse has been already reconstructed, the official documentation by the Inquiry Commission that investigated this terrible event remains secret to this day. Nevertheless, causes and dynamics of the collapse, as well as the principles and procedures followed in the subsequent fast reconstruction, can be reconstructed by cross-referencing the information provided by the newspapers of the time and by the precious Memoirs of Engineer Federico Mannucci, written in 1935, but only recently published. Mannucci's precise and competent reconstruction reveals his condemnation of the inappropriate manipulation of the 16th-century building and, above all, of the untimely perforation of the backbone wall, the main cause of the disaster