Below grade
Basements & seepage
Efflorescence, cold-joint leaks, and the difference between condensation and true water intrusion.
White powdery salts (efflorescence) mean water has moved through concrete and evaporated. It is a moisture clue, not always an emergency by itself.
Condensation on cold walls can look like seepage. Feel whether the wall is wet from outside pressure or from indoor humidity hitting a cold surface.
Roof water at the footing is a common, fixable driver. Extend downspouts, clear gutters, and improve grade before budgeting for interior waterproofing.
Active leaks, structural cracks, or sewage-related water need a licensed trade. Start with the cheap outdoor work when the pattern is seasonal and tied to rain.
Educational only — not a contractor inspection or bid. When work is structural, electrical, or involves unknown vent chases, hire a qualified local trade.