Symptoms
- White, powdery, or crystalline coating on a concrete or block foundation wall
- Coating brushes off easily but tends to return
- Sometimes accompanied by dampness or a musty smell nearby
Likely causes
- CommonWater passing through the porous concrete or blockMoisture from outside soil moves through the wall and evaporates on the inside or outside surface, leaving mineral salts behind.
- CommonGrading or gutter issues pushing water against the foundationThe same drainage problems that cause damp basements often drive efflorescence.
- PossibleHigh groundwater or hydrostatic pressureIn some areas, groundwater itself pushes moisture through the wall regardless of surface drainage.
What to do
- Brush off the deposit with a stiff brush or a diluted vinegar-water solution to see the wall surface clearly.
- Check outside for grading, gutter, or downspout issues directing water toward that section of foundation.
- Correct any drainage problems found, since efflorescence itself is a symptom, not the core problem.
- Monitor whether the deposit returns after cleaning and after the next rain.
- Improve indoor humidity control and ventilation in the basement or crawl space if dampness is also present.
- Consider a waterproof masonry coating on the interior once the exterior moisture source is addressed, not before.
- Have a waterproofing specialist assess if efflorescence is heavy, persistent, or paired with actual water seepage.
Tools and parts
- Stiff brush
- Bucket
- Vinegar (optional)
Masonry waterproof coatingSearch: “masonry waterproofing paint”
When to call a pro
Call a waterproofing contractor if efflorescence is persistent or paired with actual water seepage into the basement.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.