What Is Efflorescence on Your Stone, Brick or Stucco?

Stone mason at work

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It sparkles. It's white, sometimes with a grayish tint. It flakes off the surface and is present only on the surface. It's called "efflorescence," and it's a crystalline deposit of salts often seen on the surface of concrete, brick, stucco or natural stone surfaces. It occurs when water leaves behind salt deposits and is present on or in the masonry surface.

The word efflorescence means "to flower out" in French. In this case, it is salt flowering out of surfaces.

Where Can You See Efflorescence?

You can easily recognize efflorescence on walls, floors, retaining walls and other surfaces made of brick, stone, concrete, or stucco. It's often a white, powdery substance when seen on unsealed surfaces.

If a floor or other concrete surface has been sealed, you may see efflorescence as a white blush under the sealer. This can be especially concerning for homeowners who have sealed concrete floors.

If you're a homebuyer, a real estate home inspection would reveal whether your soon-to-be home has efflorescence. Some astute real estate agents might note efflorescence in the home, most likely to be prevalent on basement walls. Wet basements, especially, are the perfect environment for efflorescence to grow.

The Composition of Efflorescence

Efflorescence is composed of a variety of water-soluble salts. Different surfaces and different areas of the country are more likely to have particular combinations, which lead to a variety of colors.

How Does Efflorescence Happen?

For efflorescence to happen, you need water and salt. The salt comes from a range of sources. First, it may already be present inside the brick, stone or concrete. Or, the source may be the grout or cement holding surfaces together. If the surface, such as a retaining wall, is in contact with soil, efflorescence could form. Finally, it could be present in the water itself in areas with hard water.

The salt must be dissolved in water and transported to the surface of the masonry, stone or concrete. The water may already be present in the surface itself. It could also come in from outside of the surface, dissolve salts and then evaporate, which leaves behind the efflorescence.

How Can You Control or Remove Efflorescence?

There are several construction techniques that can minimize the growth of efflorescence, such as controlling the amount of water used in mortar and grout, designing with eaves and copings to direct water away from surfaces, and paying attention to landscaping and irrigation.

The best way to remove efflorescence depends on the surface and the composition of the salts. One method is to use a dry brush. For some salts, you can simply wash them away with a hand brush, mild detergent and a water rinse. Power washing is another option, depending on the surface. You may want to consult with a contractor to see if there is a recommended chemical cleaning agent for your surface and get instructions on how to use it safely. For example, a weak solution of muriatic acid might be safe for some surfaces, but it could damage others.

In general, cleaning efflorescence from a surface is an ongoing solution—much like a treatment—rather than a cure. Sealing a surface might be a solution, but if water still finds its way into the surface you could end up with spalling, which is a destructive process that should be avoided.