Musty smell after a flood or water damage event

Symptoms

• Strong musty or mildew smell in the area that flooded
• Smell persists even after the area looks dry
• Sometimes visible mold on baseboards, drywall, or flooring

Likely causes

• CommonMold growth started in wet materials before full drying occurredMold can begin growing within 24–48 hours of materials getting wet, often before homeowners finish drying everything.
• CommonWater trapped behind walls, under flooring, or in insulationSurface drying doesn't reach hidden moisture in wall cavities or under flooring.
• PossibleContaminated water (from sewage or groundwater) left residue even after dryingCertain floodwaters leave odor-causing residue that plain drying won't remove.

What to do

1. Check baseboards, drywall near the floor, and flooring in the affected area for softness, staining, or visible mold.
2. Use a moisture meter, if available, to check whether materials are actually dry throughout, not just on the surface.
3. Remove and discard porous materials that were wet for more than about 48 hours, such as carpet padding, insulation, or wet drywall.
4. Clean hard surfaces with a mold-specific cleaner after they're confirmed dry.
5. Run fans and a dehumidifier to fully dry the space, including inside wall cavities if drywall was removed for access.
6. Check for mold growth again after a week, since it can take time to become visible even in already-affected materials.
7. Call a water damage restoration or mold remediation company if the smell persists or the flooded area was large or from contaminated water.

Tools and parts

• Moisture meter (if available)
• Fans
• Dehumidifier

When to call a pro

Call a water damage restoration company for significant flooding, and a mold remediation specialist if mold has already started.

Safety