What are those powdery white areas on my brick walls?
Thursday, October 18, 2018
The discoloration is likely “efflorescence,” which is an accumulation of minerals and salts on the surface of the brick due to repeated bouts of excess water in the material. When the brick is saturated with water, the minerals that naturally occur in the masonry material are dissolved and, as the water migrates to the surface of the brick and dissipates from evaporation, the mineral deposits are left behind as a thin layer of powder. Repeated saturation and evaporation cycles lead to a buildup of the surface powder. Efflorescence can also form on concrete block walls, as shown below.
While the efflorescence is only a cosmetic problem in itself, its appearance on the wall indicates an ongoing water intrusion problem, which can lead to mold growth in adjacent building materials over time. Occasionally, efflorescence is mistaken for mold. Here’s a three ways to tell the difference between the two:
1) When a sample of efflorescence is pinched between the fingers, it will crumble into a powder. Mold will not.
2) Efflorescence grows on inorganic masonry materials, while mold does not; with the exception that a dirt/dust buildup on the surface of a moist masonry wall will sometimes grow mold.
3) Efflorescence will dissolve in water, while mold will not. One common cause of minor efflorescence is a sprinkler head that sprays on the wall, like in the photo below. A pressure washer and/or a diluted acid solution is typically used for removal of efflorescence, with the surface promptly dried afterwards to prevent reabsorption of the water.
Also, efflorescence can form on concrete that is repeated wetted, such as the garage floor in the photo below with an adjoining driveway that was incorrectly sloped to let water puddle at the garage door after every rain.
A final note: a new masonry building will sometimes have a minor efflorescence bloom, as the moisture still in the material from the manufacturing process is evaporated away during the first months following construction.
To learn more about exterior walls and structures, see these other blog posts:
How To Look At A House
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