When and how reducing moisture content for the conservation of historic building. A problem solving view or monitoring approach?

The conservation of historic buildings require to face the technical issue for preserving the historic building materials, as stated in the recent Code for protection of Cultural Heritage, in Italy (2004). Rising damp is a recurrent cause of damage, and the climatic changes are going towards the increase of humidity in the historic masonry: at 40/50° latitudes, at continental/Mediterranean climatic conditios, the alternance of dry seasons and almost monsonic seasons dramatically affects the distribution of rising damp in porous materials, as well as the water content. The evaporation of rising damp from the wet surface due to occasional or seasonal change of air temperature, causes the major damage due to salts crystallization. The evaluation of the increase of water inside the masonry is a critical issue for preventing the damages, because the presence of the water can sharply, naturally decrease in the dry seasons, as well as rapidly increases one month or more after the beginning of heavy and constant rain. The interventions against water intruding the mansonry due to water table or rainfalls that are not properly taken away from the structure are totally different, although the damages caused by both these causes are the same. Monitoring the presence and distribution of the water is useful to support the choice of the most appropriate intervention, reducing the risk to apply not effective and expensive products and preventing an oversize intervention.