Diagnosis and restoration of stone masonry

As soon as a stone is extracted from its natural, geological environment, then cut, sculpted and used, an irreversible process of alteration begins. The word "alteration" here means "change", "modification". The proximity of this stone to other materials (mortar, wood, ceramics, glass, metal, concrete...) and the variability of the environments in which it is placed, irrevocably engenders an infinite number of forms of alteration, which we set about naming, classifying, measuring and quantifying, for which we strive to identify the causes, and which we seek to cure, mitigate and stabilize.

Stone and mortar, often wrongly dissociated in the study of masonry materials, should be considered as a whole. The specific characteristics and great variability of stone as a material have led to greater interest and a richer literature than for mortar, but the present article endeavours, as far as possible, to redirect the diagnostic and restoration methods it presents, in order to deal with masonry in general.

Masonry structures represent a vast array of structures and objects, from buildings to retaining walls, tunnels, dams, bridges, aqueducts and even flooring. However, the article focuses primarily on the study of ancient stone masonry buildings, illustrating a wide range of methods.

It should be noted, however, that the term "building" is a broad one, and includes both protected structures ("Monuments Historiques" in France) and unprotected ones, all of which have in common, however, that they are old and, over the years and through use, need to be preserved, restored and maintained.

Depending on the building's level of protection, different rules, constraints and authorization procedures apply. An unprotected masonry building will be subject to the same rules for rehabilitation and works as any ordinary building. Protected buildings, on the other hand, will be treated differently depending on whether they are listed (those that are of sufficient historical or artistic interest to make their preservation desirable) or classified (those that are of public interest from a historical or artistic point of view). Project management for protected buildings will systematically be entrusted to an architect. Work on listed buildings is subject to the provisions of the French Heritage Code.

Intervention on protected buildings involves the collaboration of various players and trades, and multidisciplinarity is the key to the entire diagnostic and conservation-restoration approach practiced by architects, curators, restorers and laboratories. The Venice Charter states that "the conservation and restoration of monuments is a discipline that calls upon all the sciences and techniques that can contribute to the...