The characterisation of the materials is carried out through careful visual examination supported by non-invasive surveys that allow the surfaces to be studied and representative sampling points to be identified. Where necessary, micro-samples are taken for stratigraphic analyses and to characterise the composition of the materials. Cognitive investigations are fundamental for assessing the conservation conditions of the works. The cognitive and diagnostic investigations of the materials and climatic exposure conditions are fundamental for assessing the state of conservation of the works and planning interventions.