Efflorescence on Walls

Efflorescence is a pretty common thing in wet crawl spaces and basements. Generally it is a harmless to people but may be a sign of a waterproofing problem. It most likely will not damage the surface where it formed but may be a red flag during a home inspection.

What is Efflorescence?

Efflorescence is powder-like, white mineralized substance which forms on cinder block and concrete walls over extended periods of time that are exposed to hydrostatic pressure.

hydrostatic pressure. (hī’drə-stāt’ĭk) The pressure exerted by a fluid at equilibrium at a given point within the fluid, due to the force of gravity. Hydrostatic pressure increases in proportion to depth measured from the surface because of the increasing weight of fluid exerting downward force from above.

Efflorescence is usually made up from calcite and gypsum. It can also be seen on ground floors and it can sometimes look like foam. Efflorescence comes from aggregates, water, cements or admixtures and comes through the small cracks in the concrete or cinder block. When the concrete and block are exposed to moisture and usually the efflorescence starts forming relatively fast. It usually forms in places with high humidity levels, such as basements and crawl spaces. Efflorescence is often mistaken for white mold, but it is not mold.

Is Efflorescence a Type of White Mold?

When in a crawl space or basement it may be hard to distinguish between efflorescence and mold without performing a mold test but true efflorescence is not mold. Now, what do I mean by true efflorescence? Sometimes efflorescence can grow on painted walls and the paint may support mold growth. When in doubt perform a surface mold test and send to a mold analysis laboratory to be sure you aren’t dealing with mold.

What to do about Efflorescence?

As stated earlier, efflorescence is usually a sign that there is a water leak somewhere in the foundation. Increased levels of moisture in your basement or crawl space may be an indication of some structural damage or that the exterior membrane has failed in some way. For example, water is picking up different kind of acids when it penetrates through the soil. Soil around house is generally acidic and that makes plants grow. Concrete, on the other hand, is made of gravel, lime and sand. Lime glues the gravel and sand together. When water goes over the concrete it weakens the structure because the lime starts to break down. This ignites the chemical reaction which produces efflorescence. So, making sure your outer waterproofing membrane is intact and working properly is the best way to handle basement waterproofing.

But, addressing water issues from the outside is not always doable either from a financial stand point or accessibility. If waterproofing the basement or crawl space is not attainable from the outside then an interior waterproofing system is a great way to handle the problem.

Efflorescence is a sure sign that you have water or a leaking problem in the basement. If you notice something like this in your basement it may be a good idea to consult a professional to help solve the problem.

Can Efflorescence Cause Mold?

An active water intrusion that is causing efflorescence is also causing humidity. Humidity over 60% can cause mold to grow on secondary areas inside the basement or crawl space like floor joists, sub-floors or items being stored. Controlling humidity is crucial to ensuring a healthy home. High humidity will cause molds and dust mites to grow uncontrollably. If you have a basement or crawl space make sure you take the proper steps to keep humidity between 45% and 55%.

High humidity may also lead to a musty odor in the basement or crawl space. Your nose is telling you that mold has begun to grow so pay attention to this warning. If you want to reduce the humidity levels in your basement or crawl space, you can put in a dehumidifier or other conditioned air system. However, appearance of efflorescence suggests that there is a condition which may damage the structure, so it is recommended that the cause of the water intrusion be addressed sooner than later.

2 thoughts on “Efflorescence on Walls”

  1. So I found what I think is efflorescence under a house in crawl space. My only question is can it grow on gravel. This is a pier and beam structure with gravel blanketing the crawl space. No water is present on this side of the structure but the HVAC system had a broken duct. Would this added humidity be enough to case efflorescence or should I suppect another form of mold.

    Thanks in advance

    1. Hi Cody, I have seen mold grow on glass but it wasn’t on the glass itself but the dust and dirt on the glass. If there is an organic food source on the gravel it is possible for mold to grow on it but I am not aware of mold growing directly on gravel. Can you see any organic material on the gravel?

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