By Richard P. Kadlubowski and Coleman H. Bynum
Why should a building's façade be cleaned? The issue of aesthetics first comes to mind. After all, a clean building simply looks better than a dirty building. A clean building presents a more hospitable front - and, therefore, a more attractive real estate prospect - to the public. Just as we put our best foot forward with a neat, kempt appearance, a building looks its best when free of the grime, pollutants, and staining that shadow its most visible - and often, most vulnerable - attribute, its façade.
Of course, not all building façades warrant the same amount of care and attention. A building's location, function, and geographic and atmospheric conditions all play roles in determining the level of cleaning effort necessary to achieve the desired appearance.
Consider function: Structures that house commercial activity, in business, theatre or shopping districts, often warrant a higher degree of cleanliness than do buildings that house industrial - or less public - activities.
Furthermore, if and when it is decided a building's façade will be cleaned, it may be that only a portion - for instance, that which is visible from the sidewalk - will be cleaned. A skyscraper in Manhattan, for example, may be cleaned from the ground to the sixth floors only, limiting the cleaning effort to that portion of the building's façade that is visible to bustling commuters. Cleaning the ground floors only is a viable alternative when it may be costly - not to mention foolhardy in a pollutant-ridden, urban locale - to clean a building's façade completely.
Finally, what it takes to clean a building situated in the country is typically far less an endeavor than if that same building were located in a metropolitan area. A rural building may warrant only water soaking to remove mild contaminants (such as dirt), while an urban building would most likely require a more in-depth cleaning effort - to remove more hazardous pollutants - to achieve the same level of cleanliness.
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.
Case in point: Moisture is the primary cause of masonry decay. When moisture is coupled with soluble salts from polluted rainwaters or with atmospheric gases, the decay is accelerated. When the soluble salt dissolves in water, it travels deep into the masonry substrate through pores or cracks. Once the moisture evaporates, the salt recrystallizes, exerting tremendous pressures that break down the masonry from within.
Lastly, façade cleaning opens a building's pores and allows the normal transpiration of moisture. Moisture trapped within a masonry wall, for example, will remain there if a waterproofing coating prevents its exit. In this case, as moisture is the leading cause of masonry decay, comprehensive façade cleaning to include removal of the waterproofing coating may be the key component of a professional's effort to restore the building.
Richard P. Kadlubowski, AIA, and Coleman H. Bynum, AIA, senior architects with Hoffmann Architects, oversee a variety of façade cleaning projects for the firm. Hoffmann Architects (www.hoffmannarchitects.com) has offices in North Haven, CT; New York City; and Washington, D.C.