What is rising damp?
In this article we willll deal with capillary rising damp phenomenon, a very common pathology in all types of buildings, analyzing their dynamics and possible causes. Sometimes you will certainly have seen some strange stains on walls or, even, some peeling areas at the lower part of them. These are rising humidity classic symptoms: a phenomenon present in over 50% of buildings, without distinctions between marine or mountain areas.
How water rises
Soil water is absorbed inside the walls, through small capillaries present in building materials, starting a potentially infinite damages cycle, both aesthetic and structural. There are to two main factors for the rising: -capillarity: property of a liquid to rise inside a pipe, inversely proportional to its diameter. -ionic forces: quantity expressing the electric field intensity. Liquids, with positive or negative charge (on the basis of the composition) are attracted by materials with opposite charge. The combination of these two factors causes the water rise within masonries, against heavy gravity The more porous the materials are (for example, the tuff) and the greater the speed of masonry imbibition, while a masonry made up of compact materials (for example stone) will absorb water slowly but continuously. The type of construction or structures age have no influence on the rising camp. Even recent buildings may be affected by this problem, independently from the quality of materials used.
This phenomenon occurs in the walls, from the floor up to about 60 cm in height but can also be seen beyond 1 m in the most critical cases. Rising damp process involves water and salts (above all sulphates and nitrates) which, once inside the wall, tend to surface. In this phase water evaporates in the air and salts crystallize outside giving rise to the classic saline efflorescence, wet spots, molds, plaster bulges and peeling paints Sometimes crumbling plaster is hided with various materials (wood, marble, tiles, etc.). This system aggravates the problem since humidity, no longer able to evaporate in covered areas, continues to rise above coverings maximum height.
Humidity levels in walls
Masonries, based on their humidity percentage, are classified in: Healthy masonry: humidity percentage less than 5; Damp masonry: humidity percentage between 5 and 10; Wet masonry: humidity percentage higher than 10. A humid environment is ideal for the proliferation of mold, consisting of bacteria and spores, that causes considerable discomfort for the health of environments and of those who live there.