Diagnosis of the wooden structures of the central roof of Palazzo Madama in Turin

“[…] it is like a stone synthesis of the whole Turin past, from its origins, from Roman era, to the days of our Risorgimento” wrote the Italian poet Guido Gozzano in the early twentieth century. Palazzo Madama is in the exact center of Turin and has its original nucleus in the eastern gate of the Roman city, which was transformed into a fortified gate in the Middle Ages and later enlarged into a quadrangular castle in the fifteenth century. With the transfer of the capital of the Duchy of Savoy from Chambery to Turin, the castle became one of the residences of the ducal family. It was then decided to close the courtyard of the castle to turn it into the ballroom, covering it with a roof. The ballroom was transformed into the chamber of the first Senate of the Kingdom of Italy in the mid-nineteenth century. The current appearance of the Palace is the result of the intervention by Filippo Juvarra in the early eighteenth century, who added the baroque façade in white marble on the western side. The wooden structure subject of this contribution is the one that supports the wide roof of the ballroom. The structure consists of 12 wooden trusses and is very particular in its composition and shape. In addition to supporting the roof, the structure was also designed to support the wooden false ceiling of the ballroom below. The contribution aims to describe the entire diagnostic process, which followed the prescription in paragraph 5 of EN 17121. The timbers have been identified and the dimensional survey has been completed, including the dimensions of structural joints. In addition, the structural grading of all elements was performed by applying the visual grading rules provided in UNI 11119. Finally, biotic and abiotic degradation have been identified and characterized.