C2) ferro-cement, consisting of making two thin reinforced concrete walls connected to one another by means of metal connectors. This technique is often used to reinforce irregular or poor-quality masonrywork and is undoubtedly very effective from the mechanical point of view, however it is very invasive. The internal masonry is “lost” from every point of view, not only because it is no longer visible but above all since it is subject in time to rapid deterioration. Another negative aspect is that the new wall panel is far stiffer than the original one (and this often has a negative impact on the structural behaviour of the building).