What Is the White Chalky Substance on My Foundation Walls?

While efflorescence on your foundation wall isn't always a warning sign, it is always best to make sure there are no moisture problems
While it doesn’t affect a building structurally, efflorescence does have an impact on its appearance. There are a number of reasons for its cause.

You may have noticed some odd white discoloration on your foundation walls. Does it look like a fluffy, powdery substance that seems to be growing or spreading over time? You may feel alarmed and worried that it’s some sort of mold growth. After all, mold can release potentially hazardous spores in your basement or crawlspace.

Fortunately, it is not mold, nor is it anything toxic. It even appears on building surfaces outside your home. The substance you’re seeing on the wall surface is quite harmless and can even disappear on its own. But it can be an indication of something else going on with the concrete of your foundation walls. What you’re seeing there on your wall is called “efflorescence”.

It is important to know what is causing your case of concrete efflorescence. It can mean there is an underlying problem..

Let’s take a deeper look into what efflorescence is, how it appears, and what measures you can take to get rid of it!

What is Efflorescence?

The efflorescence on your foundation walls is actually made up of salts deposits. This comes from both natural salts in the concrete materials as well as from salt-forming chemicals that may exist within the concrete. Efflorescence can appear on brick, poured concrete, and cinder block walls. This also includes any mortar joints. But to reach the surface of your foundation wall, there needs to be water to dissolve and transport the salts.

Essentially, so long as there are both soluble salts and some degree of water or moisture migration through your foundation material, efflorescence can occur.

Water leaking through your basement wall can leave salty deposits of efflorescence after drying
When this basement wall leak dries, there’s a chance that there will be efflorescence where the wall has been wet. This is an example of secondary efflorescence.

How Does Efflorescence Appear on My Foundation Walls

As water travels through the porous structure of the concrete, it draws those salts along with it. The water reaches the surface of your basement or crawlspace wall to evaporate. In the process, the dissolved salt gets left behind on the surface of the building material. The appearance of the salty deposits may look either crystalline or powdery with a whitish color. What prompts their appearance is the presence of water, but there are a couple ways that this interaction with water can create concrete efflorescence…

Primary Efflorescence

Water is a critical ingredient in concrete mix. But when there is too much water content, the excess water and moisture must find a way out. Salt from the cement gets carried along with the water. Reaching the surface, the salty concentration will effloresce.

Secondary Efflorescence

Another way that efflorescence can appear is when there is seepage occurring in your foundation. This can either be through cracks in your foundation, hydrostatic pressure, or through capillary action. As water seeps through your foundation wall, that water will carry with it the salt within and leave deposits as it evaporates on your foundation wall.

Depending on the type of efflorescence you have happening, that will determine what course of action you’ll need to take. It could simply be the byproduct of when your foundation was first constructed. Or it could be the indication of something else happening to your foundation that requires repairs.

Cracks in the foundation will certainly need to be repaired. But hydrostatic pressure will need to be mitigated with the help of an interior basement waterproofing system or a crawlspace waterproofing system. Without a waterproofing solution, that hydrostatic pressure will build against your foundation wall whenever it rains, leading to water and moisture pushing through your foundation.

Other Causes of Efflorescence on Foundation Walls

Here are some additional ways that efflorescence may occur, particularly when masonry has been installed improperly. These may or may not apply to you, but they’re useful to keep in mind…

  • Failure to provide proper ventilation for the concrete or masonry
  • Masonry construction without proper protection against moisture
  • Joint materials are failing
  • Masonry materials were improperly stored

Removal of Efflorescence from Your Foundation Wall

If your foundation wall is experiencing primary efflorescence, one solution is a nice surface cleaning. Here are some ways that you can clean efflorescence from your foundation walls…

  • Pressurized Water
  • Diluted Vinegar
  • Brushing

If you’re intending to use a sealer to try preventing water from traveling into your foundation concrete, consider an efflorescence cleaner to help ensure that the salt deposits have been thoroughly removed before applying that sealant.

If secondary efflorescence should be the case, then the source of the seepage must be resolved. The best way to fix a seepage problem is to consult with an expert with a great deal of experience in waterproofing lower levels and foundation repair. While you could try sealing the seepage crack on your own, water might still push its way through. While efflorescence isn’t harmful to you, allowing the efflorescence and underlying water problem to continue can potentially lead to spalling. To avoid additional damage to your foundation wall, let the experts at ’58 Foundations & Waterproofing help!

Over 60 Years of Foundation Repair and Waterproofing Expertise

Since 1958, ’58 Foundations & Waterproofing has been helping people like you keep their lower levels free of groundwater intrusion while ensuring that their foundations remain strong and stable for years and years. We’ve spent the past 60 years developing our effective and long-lasting waterproofing system. With our quality products and honest methods, we offer waterproofing and foundation repair solutions that are designed to last, providing you with a safe and dry home as well as a greater peace of mind. We’ll put a stop to any water seepage your foundation may be experiencing, keeping your basement or crawlspace dry for many years to come. Contact us today for a free foundation repair estimate and a free inspection—you’ll find none can beat our expertise!



Building Science, BA-1307: Interior Insulation of Mass Masonry Walls: Joist Monitoring, Material Test Optimization, Salt Effects