Rising damp & salt damage

Understand mortar and stone decomposition

An important factor and cause of the decomposition of mortar and stone (Limestone, Sandstone, etc.,) as well as a problem in the modern building, restoration or renovation, is the movement of salts trapped in the building walls and floors.

Generally due to humidity, capillarity, inadequate waterproofing, broken pipes, etc. we can find that salts can migrate and / or crystallize when their relative humidity is altered by weather conditions. Such crystallization usually occurs on the surface of mortars and / or “soft” supports, causing their deterioration.

The concept of solubility is important when it comes to understanding the treatment and the type of salts that we can have in a building. Basically, without entering into scientific terms, solubility can be defined as the ability of a substance to dissolve in another.

The salts dissolve in water, and depending on the type of salt, the solubility of this salt is higher or lower. In this case the most abundant salt is sodium chloride (NaCl), the solubility of sodium chloride is little affected by temperature as in other types of salts, where solubility generally increases with temperature. See diagram 1.

To explain the phenomenon that occurs is that moisture enters the supports, and this water has dissolved salts inside, the water that has penetrated the supports, its natural tendency for the capillaries of the material tends to go outward, leaving behind it, the salts they had dissolved causing them to appear in their solid form. Depending on the ease of dissolving in the water that has penetrated the wall they will surface at different heights. See chart 1.

Why use tradi hc™ SP Mortar ?


Saint Astier limes are distinguished from other NHL limes, because of their low content of aluminates and other types of oxides, which other limes do not, since their hydraulicity is given by the percentage of silica and type, and you do not come from other elements like aluminates.

Saint- Astier could provide a full Desalination solution for your project, working in two coats, with:

TRADI HC™ SP Mortar and Ecomortar F.

TRADI HC™  SP mortar is designed with Lime from Saint Astier and lightweight aggregates, this way we create an open structure facilitating the water vapour permeability and occluding the salts inside the mortar. The movement of the salts from the support through the render due to the capillarity effect.

TRADI HC™  SP mortar protects the surface of the salt crystallization. It is a sacrificial mortar to protect the surface and enhance the finishing mortar.