Rafael Navarro, Serafín Monterrubio, Dolores Pereira

Granite has been one of the most used natural stones to build heritage for centuries. This is obviously the case when granite is the main regional rock, like the case in the north of the Iberian Peninsula. The sanctuary of La Tuiza in Lubian (Zamora, northwest of Spain) was built with the granite of Calabor. This sanctuary dates from the 18th century, and was declared as Cultural Interest Resource (Bien de Interés Cultural, BIC, in Spanish) in 1995. The heritage importance of this site remains in its location, in the Route of Santiago (Camino de Santiago in Spanish), attracting visitors from all over the world. This route, besides the intrinsic cultural value, always enhance the local economy. Despite the general good state of conservation of the sanctuary, the historic building has some decay problems, even if they are mainly aesthetic, like damages due to the biological colonization and moisture stains due to the infiltration of water by capillarity. In this work we present the full characterization of the building stone from both the monument and the original quarry and the qualitative description of the main pathologies that have been detected. The main differences between the stone in the quarry and the stone in the building are the physical (hydric) and the mechanical properties. Water absorption coefficient by capillarity doubles the value in the sanctuary compared to that in the quarry; other physical properties varie in a lower extend: open porosity, water absorption at atmospheric pressure and sound speed propagation are slightly higher in the and compressive strength value is lower in the stones from the building. These differences are related to the incipient decay processes affecting the historic building. Regarding the pathologies, biological colonization (e.g. lichens, mosses and plants), is scattered throughout the building, affecting more intensely the northern side, and together with the observed scaling on the western side are the main elements of decay observed in the exterior of the historic building. Inside the sanctuary, the main observed deterioration is related to the humidity due to infiltration of water by capillarity provoking conspinuous stains, and efflorescences that affect all the walls; and biological colonization in the western side walls are the main causes of decay. Authors recommend to take measures to avoid the advance of deterioration of the historic building and to protect this small site in order to maintain the cultural heritage linked to the local community.