Efflorescence - Deposits on Masonry and Concrete

The Definition of Efflorescence on Your Masonry and Stone Surfaces

Stone mason at work
Stone mason at work. Getty Images/bob davis photography

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

The word efflorescence means "to flower out" in French.

In this case, it is salt flowering out of surfaces.

Efflorescence is found on the surface, but sub-efflorescence, known as spalling, is more expensive to fix.

Where You See Efflorescence

You will see efflorescence on walls, floors, retaining walls, and other surfaces made of brick, stone, concrete, or stucco. It is often a white, powdery substance when seen on unsealed surfaces. If a floor or another concrete surface has been sealed, you may see a white blush under the sealer. This is especially concerning for homeowners who have sealed concrete floors or other solid surfaces that show efflorescence.

What is the Composition of Efflorescence?

Efflorescence is composed of water-soluble salts. It can be a variety of different 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 variety of sources. First, it may already be present inside the brick, stone or concrete. Or, the source may be the grout or Portland cement holding surfaces together. It could come from the soil if the surface is in contact with soil, such as a retaining wall. Finally, it could be present in the water itself in areas with hard water.

Now 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. Or, it could come in from outside of the surface, dissolve salts, and then evaporate to leave behind the efflorescence.

There are a variety of 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.

Removing Efflorescence

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

In general, cleaning efflorescence from a surface is an ongoing solution 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.