Moisture
White Powder on Basement Walls (Efflorescence)
Updated · Holdfast editorial
What it means
Water is passing through the wall, even if you never see puddles.
Cleaning
Dry brushing removes it; it returns until the water source is handled.
Fixing the cause
Cleaning 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.
Efflorescence vs. mold vs. mineral stains
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.
White Powder on Basement Walls (Efflorescence): follow-up questions
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.
Every home differs; editorial standards.