Waterproofing and foundations

Desalination with porous render

Salt and lime efflorescences are often seen on façades, both on rendered and untreated brick walls. These salts and carbonates are aesthetically disturbing, but can also lead to damage if left untreated.

Dissolved salts and minerals

Salts (chlorides and sulphates) and carbonates are constantly dissolved and recrystallised in a material with a flow of moisture. Salts crystallises at surfaces with a lower pressure and moisture content than on the inside of the porous structure. The salt crystals grow bigger than the pores can deal with and this results in flaking renders. Dark areas that look like wet spots are also an indication of a high level of salts in the surface withholding the water in its salt crystals. The salt crystals grow bigger than the pores can deal with and this results in flaking renders. These efflorescences should not be confused with alkaline reactions forming insoluble gels.

Desalination and porous renders

Build up render

When the salt crystallises at or near the surface, they often grow bigger than the pores can bear. One of the solutions if the salination process cannot be stopped, is to use high-porosity renders that can absorb the salts without being damaged themselves. They can be used in combination with other normal renders to ensure a uniform surface. But the capacity of the porous renders might get filled, and when salts are visible on the surface they need to be replaced.