Unsustainable Restoration: Incorrect Material Selection and Irreversible Damage in Cultural Heritage

Cultural heritage structures are shaped by the material knowledge, construction techniques, and environmental conditions of the period in which they were produced. These structures are not merely physical legacies; they are also tangible witnesses of historical knowledge and cultural identity. Therefore, every intervention performed on cultural heritage structures directly affects not only the current state of the structure but also its potential for future preservation.

One of the most critical mistakes made in conservation and repair processes is the use of materials incompatible with the original structural system. Incorrect material selection often arises from the preference for contemporary products assumed to be “more durable,” “stronger,” or “longer-lasting,” yet these choices lead to serious and irreversible deterioration in the long term.

The Concept of Material Compatibility in Cultural Heritage Structures

Material compatibility refers to the physical, chemical, and mechanical harmony of a new material used for repair or conservation with the original building material. This compatibility must be evaluated not only in terms of material strength but also in conjunction with porosity, water vapor permeability, thermal expansion coefficient, and environmental responses.

Historical building materials are generally low-strength, high-porosity systems that “work” together with environmental conditions. These characteristics are fundamental factors ensuring the structure’s longevity. Interventions made with incompatible materials disrupt this balance, accelerating the structure’s deterioration processes.

Main Causes of Incorrect Material Selection

Incorrect material selection generally arises from the following reasons:

• Misinterpretation of the technical superiority of contemporary building materials
• Prioritizing short-term structural or aesthetic gains
• Insufficient knowledge regarding the behavioral characteristics of historical materials
• Decisions focused on ease of application and cost

This approach leads to the mistake of disregarding the original material logic of cultural heritage structures and treating them like contemporary building systems.

Multifaceted and Irreversible Deterioration Caused by Incorrect Material Selection

Incorrect material selection leads not just to a singular type of deterioration in cultural heritage structures, but to a multifaceted chain of degradation where physical, chemical, and mechanical processes interact with one another. Such interventions often disregard the working principles of the structure’s original material system, aiming instead for short-term structural or aesthetic gains. However, unlike contemporary building systems, material behavior in cultural heritage structures operates in a balanced interaction that is flexible, permeable, and responsive to environmental conditions.

The use of repair materials that are harder, denser, and have lower permeability than the original building material causes stress accumulation within the structure. This situation leads to incompatible deformations between the original material and the repair material, especially during temperature changes and moisture movements; consequently, crack formation, surface detachment, and loss of original material occur. Hard repair materials transfer the load to the original material rather than sharing it; this causes deterioration to occur not in the repair material, but in the irreversible original fabric.

Incorrect choices made in binding materials are a critical factor accelerating the deterioration process. Lime-based mortars, widely used in historical buildings, act as a buffer regulating moisture movements thanks to their high water vapor permeability and flexible structure. In contrast, the use of cement-based materials instead of original lime-based mortars disrupts this natural balance, causing moisture to be trapped within the structure. Restricted moisture movement triggers crystallization processes, especially of dissolved salts; this accelerates deterioration mechanisms such as blistering, flaking, and surface loss. In most cases, these damages are irreversible and result in the permanent loss of the original building material.

Surface coatings and incompatible materials applied for protective purposes further complicate deterioration processes. Low-permeability coatings interrupt the material-environment interaction of the structure, preventing moisture from evaporating naturally. Such interventions often render deterioration invisible rather than stopping it; damage continues to progress beneath the coating. The problem is usually noticed at an advanced stage where the coating has failed or the original material has been seriously damaged; at this point, the interventions that can be made remain extremely limited.

One of the most critical consequences of incorrect material selection is that the intervention becomes irreversible. Loss of original material not only damages the historical and scientific value of the structure but also blocks the way for more appropriate and advanced conservation methods that could be applied in the future. This situation creates a clear contradiction with the principles of “minimum intervention” and “reversible intervention,” which are accepted as fundamental in the conservation of cultural heritage.

In this context, incorrect material selection should be evaluated not only as a technical error but as a scientific and ethical problem that directly threatens the authenticity and sustainability of cultural heritage.

The Ethical and Scientific Dimension of Irreversible Damage

Damage caused by incorrect material selection is not only a physical problem; it is also an ethical one. The conservation of cultural heritage requires respect for the authenticity of the structure and its future preservation possibilities. Irreversible interventions limit the conservation process irrevocably by preventing the application of more appropriate or scientific methods that may be developed in the future.

This directly contradicts the principles of “minimum intervention,” “respect for authenticity,” and “responsibility towards future generations” emphasized in international conservation texts.

Incorrect material selection is one of the most significant causes of irreversible damage in cultural heritage structures. Such interventions disrupt the structure’s original material system, leading to physical, aesthetic, and scientific value loss. In the conservation of cultural heritage, material selection should be based on scientific data, the principle of compatibility, and the concept of reversible intervention, rather than short-term gains.

Protecting cultural heritage is not about making it stronger; it is about ensuring its transmission to the future by working in harmony with it.