Efflorescence: The Ugly Stuff on Masonry & Concrete

By Owen Whetzel

Efflorescence, also known as bloom, is generally a white powdery or crystalline deposit, that forms on surfaces, such as brick, concrete, some tiles, stucco plaster, stone, mortar, and grout. It is caused, when water dissolves salts within the materials and then brings the salt-laden water to the surface, which evaporates, and leaves behind what are usually calcium sulfates. Not to get too technical, but efflorescence can also be caused by free alkalies, that leach from surrounding grout, mortar, concrete, etc.
 
The water source could be surface water or water, which is permeating through the brick, concrete, etc. from the backside. Some causes are moisture during construction (known as new building bloom); a misaligned sprinkler head; poor drainage behind a retaining wall; a leaky roof, that is allowing water behind the material; water pooling beneath a walkway or patio; or common rain.
 
Efflorescence is unsightly and could stain or erode a surface, or pose a slip hazard on a floor, but is usually not structurally damaging. However, the source of the problem -- water -- could be.
 
Professionals do not seem to agree on what is the best way to remove the ugly stuff, but they do agree on the need to identify the source of water and attempt to eliminate it. This may be as simple as adjusting an irrigation sprinkler, to not spray on a walkway or wall, or may be more complex, such as installing a drainage system. Without correcting the water source, you may be cleaning the powder away on an ongoing basis.
 
The good news is that most efflorescence, particularly that evident on new construction, usually goes away with time.
 
To remove efflorescence, use the least aggressive method first, which is to attempt to scrub the deposit away, using a non-metallic stiff-bristle brush. This can be done dry or by using clean water. If you are working on a concrete slab, brick walkway, etc. you might have success using a driveway-asphalt and stone (rough surface) push broom, otherwise use a short handle scrub brush. Wear a dust mask and eye protection.
 
An efflorescence remover, which is a chemical solution formulated for removing efflorescence, or an acid (for example, muriatic acid diluted to a 1- to 10-percent solution), should be used by a professional, who routinely analyses the cause of the problem, corrects it and then attempts to remove the efflorescence, using the proper method.
 
Can you seal a surface against the formation of efflorescence? In some instances, yes, if you have determined the cause is from surface water and not water permeating up through the material. Do not apply a paint or sealer over a surface with visible efflorescence.
 
When applying a sealer, apply one that allows moisture to pass through and one that doesn't contain silicone (silicone can seal moisture in, which can lead to accelerated deterioration of brick, concrete, etc.).
 
                                                                               ●
 
For more information:
 
The most comprehensive directory of information on efflorescence I've found is "Efflorescence -- A Synopsis of the Literature," by F. MacGregor Miller and John M. Melander. It is publication SN2515a from the Portland Cement Association, (http://www.cement.org/bookstore/profile.asp?store=&pagenum=1&pos=0&catID=&id=6820), 5420 Old Orchard Rd., Skokie, Ill. 60077-1083. Phone (847) 966-6200. E-mail: info@cement.org.

Owen Whetzel has earned an outstanding reputation as an expert among both professionals and do-it-yourselfers, in his writing and lecturing about building, remodeling, home improvement, woodworking and do-it-yourself projects.

Owen has collaborated on books and magazine articles, was a regular guest on The Discovery Channel's highly successful home repair show, "Fix-It Line," and from 1991- 2000 he hosted "Wednesday How-To Night" on San Jose's PBS-TV affiliate, KTEH. 

He has written columns on home repair for the San Jose (Calif.) Mercury News. In 1990, he was honored to have contributed to the newspaper winning the Pulitzer Prize (General News Reporting), for its detailed coverage of the October 17, 1989 Bay Area earthquake and its aftermath.