VILLA IL TREBBIO

Given that these stone elements are exposed to environmental weathering and considering the specific nature of the material—in this case, Pietra Serena—the most appropriate methodology was selected based on the type of degradation encountered. Every phase of the intervention (before, during, and after) was photographically documented, both in general views and close-up details.

The intervention began with the following operations:

• Verification of the stability of individual elements, old grouting, and integrations (*);
• Removal of unstable reconstructions and old, failing grouting;
• Treatment and removal of biological patina through the application of BIOTIN T biocide in a 2% aqueous solution;
• Removal of loose surface deposits by dusting with soft-bristle brushes;
• Removal of coherent deposits via hydro-washing with demineralized water. Specifically for the windows and the main portal inside the loggia, cleaning was performed using a poultice of ammonium carbonate (15% aqueous solution) supported by Arbocel (80%) and Sepiolite (20%), with a 4-hour contact time followed by thorough rinsing. This method was chosen as these surfaces exhibited a cohesive, altered patina that could not be removed by simple washing;
• Surface consolidation through the application of ethyl silicate by imbibition until full saturation;
• Structural bonding and consolidation of elements or blocks at risk of falling, using fiberglass or stainless steel (AISI 304/316) threaded rods (Ø8mm) and EPO 121 two-component epoxy resin;
• Surface grouting with a mortar composed of lime and stone dust (1:2 ratio), with the addition of natural earths as pigments to match the stone’s original tone;
• Chromatic integration of new repairs and stable old integrations using lime-based glazes (velature) and pigments.

(*) Structural Note: During the initial phase, a significant issue was identified regarding the windowsills and cornices on the first floor. This was due to the exfoliation (scaling) typical of Pietra Serena, which in this specific case occurred horizontally. The size and weight of the scales were considerable—reaching up to 6 kg—making standard consolidation with threaded rods impossible. Consequently, a structural consolidation proposal was developed in coordination with the Works Management (Direzione Lavori) and submitted to the SABAP (Superintendency), which granted formal approval.

The approved intervention involved:

• Dismantling of fragments at risk of falling;
• Consolidation of both the substrate and the fragments using ethyl silicate until saturation, followed by reassembly and bonding;
• Installation of stainless steel support frames according to the technical drawings;
• Reconstruction of missing parts to minimize the visual impact of the steel supports, followed by a faux-stone finish applied to the metal frames.

Additionally, structural issues were identified on the loggia columns; these specific works were referred to structural engineers and specialized contractors.

The stone elements on the façades of Villa il Trebbio are in a poor state of conservation. This condition is likely due to previous interventions—such as renovations or functional adaptations—environmental weathering, natural phenomena like earthquakes, the inherent nature of the stone itself, or simply the passage of time. These factors have resulted in various types of surface degradation, including:

• Erosion due to wear and missing parts;
• Biological patina and both coherent and incoherent surface deposits;
• Chromatic alteration and material disintegration;
• Exfoliation, fracturing, and cracking;
• Staining and scaling (exfoliation).