"While aesthetics is the obvious - and primary - reason for cleaning a building façade, the effort to expose the substrate for evaluation and repair runs a close second. It is nearly impossible to gauge the condition of a masonry substrate, for example, when the façade is covered in dirt, grime, and/or a coating. In order to determine those areas that need to be patched, repaired, or resealed - or, in some cases, to even properly identify the substrate - the façade should be cleaned of any and all elements that preclude its proper evaluation.
Still another key motivation behind façade cleaning is the effort to remove damaging pollutants such as sulfur and nitrogen oxides, and other acid rain pollutants, from the façade. These pollutants serve to accelerate façade deterioration."
Read this article at: http://www.buildings.com/article-details/articleid/474/title/fa%C3%A7ade-cleaning.aspxRead More