AbstractThe use of mortars and plasters has been widespread in many cultures for thousands of years and these materials are found in the vast majority of built cultural heritage. They play a crucial role in the preservation of immovable heritage and must be taken into great consideration when conserving historical buildings. Plasters and mortars have been extensively studied from a chemical and mineralogical point of view. The main causes and mechanisms of damage and deterioration are understood and various methods and materials have been developed for their preservation. Treatment development, testing and evaluation in the laboratory, under controlled conditions, has produced a high level of knowledge. However, there is a divergence between the results of academic-scientific studies and practice in the field. Laboratory studies typically tackle only a few variables at the time and the results cannot always be directly applied to address the complex problems that restorers face in their daily work practice. In addition, in situ conservation-restoration is extremely challenging because many of large number of variables involved cannot be controlled or modified. Following a description of the ideal “value-based” conservation process, this compilation work discusses aspects related to understanding deterioration mechanisms and planning of preventive and remedial interventions in a way that may be useful to update conservators-restorers on the status of scientific research in this field, and to guide conservation-scientists to identify unresolved issues, which require future research efforts.