Facade conservation works, which we frequently see in conservation practices, aim to transfer historical buildings to the future with confidence by repairing the outer layer of the building, which is heavily exposed to environmental factors.
Stone is used as the main building material in most of our historical buildings that have survived to the present day. Natural stones, which are seen throughout the bearing walls (cut and rubble stone masonry) or on the wall surface as cladding, face natural and man-made deterioration factors since the end of the construction of the building. These types of deterioration, which are frequently seen on facades due to their openness to external factors, can threaten the integrity of the building and the historical material. A wrong decision that may be taken in conservation studies carried out to protect the integrity may cause irreversible damage to the original material and loss of material. For this reason, facade conservation works should be carried out under the guidance of a conservation report prepared by expert conservation workers.
The most common types of deterioration in stone facades include, but are not limited to, the following:
- Cracks are caused by the lithological characteristics of the stone, structural load, climatic effects and corrosion of metal elements and may appear as hairline cracks, deep cracks, crack networks or structural cracks.
- Joint discharges occur in stone and brick masonry mortars and can cause problems in architectural elements.
- Efflorescence and the formation of salt crystals under the surface; occurs as a result of the evaporation of water in the structure and the accumulation of salt in the water on the surface, pores and cracks of the material. Improper use of mortar materials and environmental factors (wetting-drying cycle, minerals in soil, air pollution, sea water, animal wastes and antifreeze salts) play an important role in these formations. The most common salt types are those containing sodium, potassium and magnesium.
- Crust formations create a different morphology and color on the surface. In the black crusts formed by the interaction of acidic gases caused by air pollution and minerals in the stone, external substances coming into the structure as a result of pollution also accumulate. On the other hand, in some encrustations, water-soluble minerals and oxides coming from the building material accumulate on the structure as water evaporates from the surface.
- Surface pollution is formed by the accumulation of particles brought to the surface by air pollution and other factors and can cause crusting.
- Biological formations are the formation of plants by carrying seeds to the structure through wind and living organisms, and the formation of algae, lichens and mosses on the surface. Especially plants can cause extensive damage to masonry elements through their roots.
- Discoloration; occurs when the building material is exposed to climatic factors and humidity or when it encounters undesirable substances such as salts, corrosion products and microorganisms.
- Loss of surface and material is caused by user-induced damage, the above types of deterioration, and deterioration such as dusting, pitting, and foliation, which cause loss of surface and material in stone.
The report prepared for the intervention includes in-situ observation information and laboratory analyses, and presents intervention recommendations based on this information. In the first phase of this study, macro-observations are made, deterioration mechanisms are systematically documented and samples are collected to assess the state of preservation of the cultural property. If there are tests and observations that need to be carried out at the site, non-destructive experiments are carried out where necessary and where possible, and micro-observations are carried out with portable devices. The collected samples and the analyses and tests carried out within the scope of the conservation report enable the characterization of the original building materials and the types of deterioration. The laboratory uses physical, mechanical and chemical tests, microscopic observation and advanced analysis techniques. Restoration materials proposed prior to intervention are also characterized, and the compatibility of new materials and repair methods with the original building material is checked. The impact of these interventions on the original material should be tested on samples obtained from the building for analysis or in designated areas of the building.
Depending on the type of deterioration, different conservation approaches such as surface cleaning, removal of attachments, consolidation works, plastic repair (for material loss in stone, brick and joints) can be selected in intervention proposals. Surface cleaning, plastic repair and consolidation works, which are common in repair works, are guided by the analysis data provided by the conservation report and expert opinions. In case of deterioration such as crust formation, surface contamination and discoloration, mechanical, chemical or laser-based cleaning methods that are most suitable for the building material are selected in line with the report. Factors such as the pressure applied, type of abrasive, solvent properties, beam wavelength and application procedure are important in these methods and the necessary guidance on these issues is provided in the report.
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