Signs to look for
- A musty, earthy smell that's stronger in one room or when the heat or AC runs.
- Stains, spots or discoloration on walls, ceilings or baseboards.
- Paint that bubbles or peels, or drywall that feels soft.
- Warped baseboards, cupped wood floors or loose tile.
Why mold hides after a leak
When water soaks into drywall, insulation or a subfloor, the surface can dry in a day while the inside stays wet for weeks. Mold needs moisture and something to feed on, and the paper face of drywall and wood framing are both. The EPA advises drying wet materials within 24 to 48 hours to prevent mold growth. Leaks that went unnoticed, or were dried with a fan and a guess, are where hidden mold usually starts.
The signs, in more detail
Smell
A musty smell is often the first and only sign. Notice whether it's stronger in one room, inside a closet or cabinet, or when the heating or air conditioning kicks on.
Stains and discoloration
Yellow or brown rings on a ceiling, dark spots near baseboards, or gray shadows on a wall behind furniture can mean water is still getting in or mold is growing behind the surface.
Paint and drywall changes
Bubbling or peeling paint, drywall that feels soft when you press it, or seams that are splitting all point to moisture behind the surface.
Floors and trim
Cupped hardwood, swollen baseboards and loose tiles near a bathroom or kitchen often mean water got under the floor.
Places to check after any leak
- Under kitchen and bathroom sinks, and behind the dishwasher and refrigerator.
- Around toilets, tubs and showers, including the ceiling below them.
- Basement walls, the bottom of finished basement drywall, and under carpet.
- Attics under roof leaks, and around windows.
When to call a professional
The EPA suggests homeowners can often clean small areas, roughly under 10 square feet, on hard surfaces. Call a professional when:
- The area is bigger than that, or you suspect mold inside walls or under floors.
- The water was sewage or otherwise contaminated.
- You smell mold but can't find it. Air sampling can help locate it.
- Anyone in the home has health concerns. Talk to a doctor about symptoms.
Mold removal only lasts if the moisture source is fixed and the area is dried. That is the part most do-it-yourself cleanups miss. See our mold remediation and air quality testing services.
Common questions
Do I need a mold test?
If you can see mold, you usually don't need a test to know it's there. Testing helps when you smell mustiness but can't find the source, or after remediation to confirm the air is back to normal.
Can I clean mold myself?
The EPA says homeowners can often clean small areas, roughly under 10 square feet, on hard surfaces. For larger areas, mold inside walls, or mold from sewage or contaminated water, the EPA recommends a professional.