Efflorescence is a very common problem with poured concrete foundations. The white powdery substance you see along the outside of your basement wall is efflorescence and indicates moisture is in contact with the masonry. Don’t worry this unattractive build up isn’t hazardous; efflorescence is simply salt and can be easily removed with efflorescence removers or other cleaning techniques.
This does not necessarily mean that intrusion will occur. We recommend checking gutters, downspout drain lines for proper operation. Efflorescence is found on many homes without water intrusion occurring inside the home. But, it should alert you to the possibility that future steps may be needed.
What is happening, water infiltrates the block or the concrete wall and as water evaporates from the surface the mineral deposits are left behind in the form of white substance. Although efflorescence is generally a visual problem, if the efflorescence crystals grow inside and under the surface, it can cause spalling of the foundation wall, which is when the surface peels, pops out or flakes off. The salt pushes from the inside out and can eventually cause crumbling and deterioration.
Efflorescence, water-soluble salts come from many possible sources. First of all; there must be water present to dissolve and transport the salts. Groundwater is often a source of efflorescence. For water to carry or move the salts to the surface there must be channels through which to move and migrate. The more dense the material more difficult for the water to transport salts to the surface. On the other hand, the more porous the material, the greater the ease with which salts are transported and deposited. Salt-bearing water, on reaching the surface of a structure, air evaporates to deposit the salt.
When humidity is low, the water may evaporate before reaching the surface of the structure, leaving the salt deposit beneath the surface, and unseen. When the humidity is high, water evaporation is slower allowing more opportunity for salted to be deposited.
Since humidity has a definite effect on whether or not the salts appear, it can be assumed that efflorescence is a seasonal problem. The intensity of efflorescence increases after rainy winter seasons, decreases in spring, and by summer has practically disappeared. This cycle may repeat for months or years, but generally the intensity of the efflorescence decreases in all but very extreme cases, and by about the third year it should be practically eliminated.
Again I repeat, this does not necessarily mean that intrusion will occur. Checking the exterior for grade issues and low spots, ensuring the proper operation of downspouts and that water is being directed away from the foundation may help prevent efflorescence on the exterior of your foundation wall.