Documentation and assessment of the most important conservation treatments carried out on Lecce stone monuments in the last two decades

Lecce is the most important town in the Salento region (South-East of Italy, on the Adriatic sea). It mostly flourished in the Baroque period (late XV - XVII cent.). The local "Lecce limestone", a very porous, soft calcarenite, was used for the majority of the monuments, mansions and humble private houses in the historical town centre. In the 1980s and early 1990s, extensive conservation treatments were carried out on the facade of the S. Croce church, the most important Baroque monument of the region. In total, the intervention lasted about 10 years and included (beside the structural reinforcement by cement injections and stainless steel bars) cleaning, gap filling, pasting of loose fragments, consolidation and water proofing of the stone surfaces. The approach and the methodology adopted for S. Croce served as model, with further modifications and improvements, for the conservation treatments that were carried out in the following years on many other monuments in the town centre and in the region as well. Differently from what used to occur in the past, these works were recorded even if the accuracy and the reachness of details are uneven for the different monuments. Thanks to the homogeneity of the monuments (all pertaining to about two centuries), of the stone and its state of decay, and of the conservation treatments carried out in a relatively limited lapse of time, Lecce nowadays offers the unique possibility of assessing the durability of those treatments on a rather large statistical basis. The paper illustrates the decay problems of the calcarenite and the products used for the different treatments on seven monuments. This information is extracted from the documentation available at the local Superintendency, from the relevant bibliography and from interviews to conservator/restores who carried out the works. Further to that, visual examination and simple non-destructive tests were carried out on some monuments from the ground level and from accessible balconies, windows and terraces. These observations are useful for a first assessment of the present conditions. A more detailed methodology is also proposed for a better evaluation in view of the maintenance programme. The results of such an assessment will also be useful to compare the actual behaviour of the treated stone in the monuments with the results of laboratory tests that were carried out in the 1980s for the selection of products for consolidation and water proofing treatments of the S. Croce facade. From such a comparison, useful indication on how to improve the laboratory tests could be obtained, as far as the artificial weathering and long term durability are concerned.