Maintenance of facades

Maintenance, cleaning and restoration work for old stone façades requires good knowledge of the materials used, and the different types of dirt, surface deterioration and degradation that can affect them, both by the specifier and the contractor.

Stone façades are cleaned to eliminate surface dirt and wherever possible water soluble salts contained essentially in the first few millimeters, without damaging the quality of the stone, while respecting its surface condition as much as possible. This operation must be done carefully. It is recommended that a preliminary study should be carried out to make analyses on samples and/or tests on small areas, wherever possible.

The cleaning method should be chosen as a function of the treated façade, its historical value, its cornice design, the nature of the stone, its preservation condition, and the severity and nature of dirt accumulation. It should almost never be done without a preliminary study.

The cleaning method used should not be rough; it must not cause severe abrasion of the cleaned surfaces, or micro-cracks. The exposed stone would be made more sensitive to external aggression such as atmospheric pollution (elimination of incrustation).

It must not cause secondary reactions (efflorescence or crypto efflorescences) that are always unattractive and can compromise the condition of the façade. Long experience has shown that the best method of avoiding these disorders and evaluating the efficiency of the different cleaning processes is to carry out comparative tests on the façade to be resurfaced a few weeks before the cleaning operation itself, because undesirable secondary reactions may not show up immediately. These prior tests will help to precisely adjust the methodology to be followed so that an accurate cost estimate can be made for the operation.