Non destructive techniques for the conservation of stone staircases in historical buildings

The transition of buildings over the first decades of the 20th century from traditional materials to industrial techniques was quite crucial. In fact, such a change meant to overcome a well established technical culture toward a new design and construction approach. As a consequence, it has led to several relevant problems, which should be carefully evaluated in order to ensure the conservation and safety of such buildings. The present paper is going to focus on staircases, which are among the most critical constructional elements, for variety and complexity of mixed technical solutions and for structural vulnerability. Specifically, it will provide with an overview on the investigation of stone cantilever staircases and iron/brick landings in a representative case study, the public housing complex “Duca degli Abruzzi” (Bari, Italy), consisting of 11 residential buildings, dating back to 1908-1931, and 34 stairways. The investigation will involve the classification of construction materials and techniques, the identification of decay and damage and the application of ultrasonic pulse velocity testing, in order to assess the state of conservation. The results analysis will address pros and cons of the investigation technique for the specific purposes, as well as a qualitative performance evaluation of the structures.