Wall moistening:

Relations between the moisty wall and the salt load

In general, the structure of the building’s main and cellar walls as well as the surrounding ground have a similar capillary system. For this reason and as a consequence of a number of different factors the water seeping into the ground is able to move upwards through this connected capillary system in the form thin salty solution. This flow of ground water transports the old contaminations of the soil along with the hazardous compounds seeping recently into the ground. These contaminations in the form of different salts accumulate in the reeking zone. Most part of these salts is of hygroscopic character, i.e. is able to extract moisture content from everywhere, even from the ambient air. As a result of this effect, the wall surfaces become wet, which may dry out again as soon as the moisture content of the ambient air has decreased. As a consequence, the appearance of wet spots in the upper zone of the wall indicates the presence of harmful salts. Accordingly, the size of places and the degree of damages greatly depend on:

  • the capillary contamination moving within the wall. In the clean water more molecules are present connected to each other in the form of aggregates. Consequently, these are able to penetrate only into capillaries with larger diameter. The mixture of water and salts is present in a dissociated form, i.e. the molecules are separated from each other. As a result of this, the molecules will be able to penetrate into capillaries also with smaller diameter.
  • the material of the wall and the diameter of capillaries developing in the wall. Within the tight capillaries of hard stone walls the water is able to move upwards only to small heights because the small quantity of water rapidly evaporates out from the wall. In wall materials with large diameter capillaries the water remains on low levels because there is only the sucking up force prevailing there resulting in high concentration of water in the capillaries. In the wall with capillaries of medium diameter the thin salt solution is able to move upwards even for more meters as a consequence of conditions discussed before.
  • the micro climate of evaporation. On the outside surfaces exposed to sunshine and wind, as well as on the inside surfaces close to the heating bodies the concentration of salts increases as a result of increased movement of moisture generated by the intense evaporation and damage the surfaces. At the same time, the outside surfaces shaded by trees or other buildings, or the buildings that have been unoccupied for many years or the wall surfaces of rooms without heating are tending to evaporate less moisture. Consequently, the accumulation of salts is also decreased which is demonstrated in a wall damage of less degree, as well.

Fundamental problem of walls becoming moisty

Detailed exploration of wall moistening