What's That White Stuff on Your Foundation? What to Know About Efflorescence

If your bricks or cement foundation blocks have suddenly developed a white, gray or yellowish appearance, don't worry, they didn't fade overnight. What you're seeing is commonly known as efflorescence, a substance that forms on cement, bricks and natural stone when their natural salts come in contact with moisture.

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Efflorescence is fairly easy to remove with some standard household tools. However, you'll also need to treat the underlying moisture issue, which may require professional intervention.

What Is the White Powdery Substance on the Bricks or Cement Blocks of My Foundation?

The white powdery substance that develops on bricks and foundation is called efflorescence. It develops when the natural salts in bricks, cement blocks and other porous materials mix with moisture and move toward the material's surface. When the water evaporates, the efflorescence (white powdery substance) remains.

Efflorescence generally appears as a white or grey powder, but it may also have a yellow or brown tint if exposed to different types of salt or underlying ground soil. It can develop on interior and exterior bricks and foundations, and the moisture source must always be addressed to prevent its return. Since it forms from natural salts, efflorescence itself doesn't pose any health risks, but the excess moisture can lead to issues like mold and mildew growth, dust mite infestations and possible structural damage.

How Does Efflorescence Form?

Efflorescence forms when soluble salts dissolve in different types of porous foundation materials, including brick, concrete and mortar. The salts dissolve when they come in contact with a moisture source such as rain or groundwater. The saltwater then travels through the porous material and evaporates, leaving behind a white, chalky residue called efflorescence.

With new construction projects, efflorescence can form if building materials like bricks and cement blocks are left out in the rain or exposed to damp soil during the building process. Efflorescence can also form over time on older structures during freeze-thaw cycles, especially if the bricks or foundation have minor damage or moisture issues.

Is Efflorescence Harmful?

Efflorescence is not considered harmful to human health. However, since its presence often indicates a moisture issue, you should always deal with efflorescence buildup as soon as possible to reduce the risk of structural damage.

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How Do I Remove Efflorescence From Brick or Foundation Blocks?

The first step in removing efflorescence on foundation is to identify and eliminate the moisture source. Once you determine where water is entering your bricks or foundation, you'll need to repair and seal any cracks and waterproof the area. If the efflorescence issue is in your basement, you may also want to install a humidifier.

It's important to note that foundation repair and waterproofing are both extensive projects that require specific equipment, skills and expertise. If you're not an experienced contractor, it's best to call in a specialist to waterproof the affected areas and perform any necessary foundation repairs.

Visible efflorescence deposits can usually be removed with a stiff brush, while deeper, set-in crystals may require scraping with a putty knife. If you plan to remove the efflorescence as a DIY project, it's a good idea to wear a mask and safety goggles. This will help prevent the powder from getting in your eyes and mouth as you scrape it off the building materials.

Efflorescence Removal: Step by Step

• Dry brush and scrape the affected area. Use a stiff brush and a putty knife to remove as much buildup as possible from your foundation.

• Apply cleaning solution. Apply a solution of one part white vinegar and one part water to the foundation. You can also use a commercial masonry cleaner or grout haze remover if you're dealing with extensive buildup.

• Scrub away buildup. Using a scrub brush, gently scrub away any remaining efflorescence.

• Rinse and dry the affected area. Rinse the treated area with clean water and allow the foundation to dry. If indoors, consider using a fan or dehumidifier to ensure the foundation dries completely.