What Is That White Fuzzy Stuff Growing on My Basement Wall?

Efflorescence looks like a white, chalky powder or fuzzy crystals on concrete or brick walls. It forms when water moves through the wall, carrying dissolved salts to the surface, then evaporates. To test, spray a little water on it; if it dissolves or wipes off easily, it's likely efflorescence.

Mold, on the other hand, often appears as black, green, or white fuzzy patches that don't dissolve in water. If you suspect mold, avoid touching it or stirring up spores. A mold professional can identify it and advise on safe removal, especially if the area is large or you have health concerns.

For efflorescence, a stiff brush and water can remove the surface salts after you've addressed the moisture. If mold is present, do not scrub dry, as that releases spores. Use a damp cloth with mild soap and water for small patches, and wear gloves and a mask for protection.

Never mix cleaning products or use bleach on porous surfaces without ventilation. If the growth covers a large area or you feel unwell, see a doctor and call a mold professional. They can assess the extent and recommend proper containment and cleaning methods.

Start by managing water outside your home. Extend downspouts away from the foundation, ensure gutters are clean, and slope the soil so water drains away. Inside, use a dehumidifier in the basement to keep humidity levels low, especially during wet seasons.

Check for leaks regularly, including around pipes and windows. Pay extra attention after heavy winter rains, when the ground is saturated. Sealing interior walls with a waterproof coating can help, but only after the moisture source is fixed. Persistent problems may need a foundation expert.