Wall humidity – Part 2/2

Umidità - VimarkAmong the different types of moisture that can affect the walls of a building, one of the most common causes of structural degradation is defifinetly rising damp by capillary action.

The project of renovating damp and saline walls of a building affected by rising damp can be summarized in three distinct types of intervention: interception and water drainage procedure, horizontal barrier procedure, electroosmosis and dehumidification and moisture management procedure.
In the first case the walls involved are solely perimeter load bearing, when possible, avoid the water reaching the wall by inserting cavities, well areated crawl spaces, vents, drains etc.

Umidità - VimarkHorizontal blockade instead is carried out by mechanical cuts or chemical barriers making a “cut” within the wall, along its entire length and thickness, which prevents the rising damp to rise by capillary action across the entire wall. In the case of chemical barriers a special formulated chemical liquid is inserted which will react or on the porosity of the construction materials, blocking the pores and capillaries, or with strong hydrophobicizing effects that reduce the power of capillary absorption.

However with this cycle it is difficult to achieve a good result due to the many variables that can occur on site when being applied. The cycle does not assure a total penetration of the resins which may decrease when the thickness of the wall to be restored is increased. Furthermore more or less intense preferential accumulation may occur due to the type and homogeneity of the materials that make up the wall, in addition, in the presence of internal macroporous voids, as with rubble masonry for example, large amounts of resin is required to saturate the gaps.

Electroosmosis is a physical principle that involves the movement of a liquid through a capillary as a result of the application of an electric potential difference. Low-voltage electrodes are applied to the masonry changing the polarity of the ground and the masonry, intervening therefore on the rising damp by capillary action.

Instead, dehumidification and rising damp management techniques act on the wall surface, significantly increasing evaporation properties through the application of macroporous dehumidifying plasters that do not inhibit the process of rising damp, but dramatically increase water evaporation from the wall to the outside.