Moisture
White Powder on Basement Walls (Efflorescence)
Updated · Holdfast editorial · 2 min read
What does it mean?
Water is passing through the wall, even if you never see puddles.
How should it be cleaned?
Dry brushing removes it; it returns until the water source is handled.
How do you fix the cause?
How do you clean it off?
Dry-brush efflorescence with a stiff brush, then address the moisture source. Avoid sealing over it with paint; trapped moisture pushes coatings off the wall.
Is it efflorescence, mold or a mineral stain?
Efflorescence is mineral salt carried to the surface by water moving through concrete, block or stone, left behind as a white, chalky powder when the water evaporates. It's common on Mahoning Valley block and sandstone basement walls in spring. Mold looks and behaves differently: it's organic, grows in patches, often smells musty, and can be gray, green or black.
Call a professional if
- Water coming through a crack that's widening or displaced
- Walls bowing inward or cracks in a stair-step pattern
- Standing water near electrical panels or appliances
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About basement waterproofingWhat else do people ask about this?
Is efflorescence mold?
No. It's mineral salt left behind when water evaporates. Mold is fuzzy or slimy and organic.
Does efflorescence mean my basement leaks?
It means water is moving through the masonry. It may be seepage or damp soil against the wall.
How can I tell efflorescence from mold?
Efflorescence is white, powdery and dissolves in water; mold is fuzzy or slimy and often gray, green or black.
Does efflorescence come back after cleaning?
Yes, as long as water keeps moving through the wall. Fixing the moisture source is the only lasting fix.
Where can I verify this information about your home?
- 1U.S. Environmental Protection Agency: MoldGuidance on moisture control and keeping indoor humidity low to prevent mold.
- 2U.S. Environmental Protection Agency: RadonWhy basements in your home should be tested for radon, and how sealed sumps fit with mitigation.
- 3Federal Trade Commission: Hiring a ContractorWhat to check before hiring: licensing, insurance, written estimates and payment terms.
Every home differs; editorial standards.