White powder on basement walls (efflorescence)
Urgency
2/5
Depends on what you find — start here$0–$1,500Typical repair cost
Likely causes, most common first
- Efflorescence: minerals left behind as moisture migrates through masonry — the wall is telling you water passes through it
- Damp soil against the foundation from grading/downspout problems
- Normal curing in newer concrete (fades over time)
Do this right now
- Brush it off dry and mark the area — returning powder = active moisture path
- Walk the outside: downspouts, grading sloping TOWARD the house, hose bibs — fix the cheap causes first
DIY or call a pro?
Efflorescence itself is harmless; ignoring its message before finishing a basement isn't. If exterior fixes don't stop it, interior sealing or drainage advice is a short professional visit that prevents a very long regret.