Signs of Mold in House: A Room-by-Room Checklist

Mold spores are everywhere. The EPA says it is impossible to get rid of all mold and mold spores indoors. What turns spores into a problem is water. The CDC says mold will grow where there is moisture, such as around leaks in roofs, windows, or pipes, or where there has been a flood, and it grows on everyday materials like paper, cardboard, ceiling tiles, and wood.

So when you look for mold, look for moisture first. Every sign below is either mold itself or a clue that water is where it shouldn't be.

The Texas humidity factor

Texas homes, especially along the Gulf Coast, face extra moisture. The CDC says "there is always some mold around", and that mold will grow where there is moisture, such as around leaks in roofs, windows, or pipes, or where there has been a flood. Finding a little mold isn't unusual. Ongoing growth is the signal to act.

Indoors, the EPA recommends keeping relative humidity below 60 percent, ideally between 30 and 50 percent. Storms and flooding add to the risk, because the EPA says you should dry water-damaged areas and items within 24-48 hours to prevent mold growth. If your home flooded, read our mold after a flood in Texas guide.

1. Visible growth (any color)

The most obvious sign of mold in a house is mold you can see. Don't look only for black. The CDC says mold can look like spots of many different colors, and the EPA says molds come in many colors including white. It can look fuzzy, slimy, powdery or like dark specks. Color doesn't tell you how risky it is, as our black mold guide explains.

2. A musty smell

The CDC says mold can smell musty. The EPA says a moldy odor suggests that mold is growing in the building and should be investigated, and that you may suspect hidden mold if a building smells moldy, but you cannot see the source. See our mold smell in house guide for tracking down the source.

3. Water stains and wet spots

Brown or yellow rings on ceilings and walls mean water got in. The EPA says don't ignore wet spots or water stains, and New York City's health department lists water leaks and stains on walls as a sign of a moisture problem.

4. Peeling, bubbling or cracking paint

In the EPA's example, water from a roof leak has seeped into a wall, causing the paint to buckle and peel. Paint can also hide mold: the EPA says do not paint or caulk moldy surfaces because paint over mold is likely to peel.

5. Condensation on windows, pipes and cold walls

The EPA says condensation on windows can be a sign of high indoor humidity. Mold is frequently found on walls in cold corners behind furniture where condensation forms. Sweating cold-water pipes are another clue; the EPA suggests you cover cold surfaces, such as cold water pipes, with insulation.

6. Warped floors, swollen walls or soft cabinet bottoms

NYC's health department lists swollen or warped walls or floors as a moisture sign. Under sinks, the EPA notes that leaking pipes under the kitchen sink can lead to mold growth in areas such as walls or cabinets.

7. High indoor humidity

If your humidity stays above 60 percent, mold has what it needs. The EPA says relative humidity can be measured with a moisture or humidity meter. Watch your closets: high humidity can cause mold on furnishings or clothing. A dehumidifier for mold can help bring a damp room down.

8. Health signs (with an important caution)

Some people notice symptoms that ease when they leave home. For some people, the CDC says mold can cause a stuffy nose, sore throat, coughing or wheezing, burning eyes, or skin rash, and people with asthma or who are allergic to mold may have severe reactions.

But these symptoms have many causes, and the CDC also says damp and moldy environments may cause a variety of health effects, or none at all. Treat symptoms as a reason to check the house, not as proof of mold. If symptoms continue, see a doctor; the CDC says people with persistent symptoms should see their physician. A mold test of your home can't diagnose illness. Our black mold symptoms guide has more.

Table: signs of mold in house checklist, room by room.

You can do a solid first check yourself before calling anyone.

1. Walk every room with a flashlight. Use the checklist above. Look low (baseboards, under sinks) and high (ceilings, tops of walls).
2. Smell for musty spots. Note where the odor is strongest and when, such as after rain or when the AC starts.
3. Measure humidity. A humidity meter tells you if a room is above the EPA's 60 percent line.
4. Check after storms. Look at ceilings, windows and exterior walls within a day or two of heavy rain.
5. Know where hidden mold lives. The EPA lists hidden spots such as the back side of drywall, wallpaper or paneling, the top side of ceiling tiles, the underside of carpets and pads, and inside ductwork.
6. Don't rip things open. The EPA warns that investigating hidden mold requires caution since disturbing moldy areas may spread mold throughout the building.

What about home test kits? The EPA says in most cases, if visible mold growth is present, sampling is unnecessary, and the CDC does not recommend mold testing in general. Our mold test kits guide explains what a kit can and can't tell you.

If the mold is small and visible: clean it yourself

The EPA says you can usually handle it yourself if the moldy area is less than about 10 square feet. In Texas, TDLR says areas of visible mold of less than 25 contiguous square feet can be cleaned up by people who are not licensed. Fix the water, then scrub mold off hard surfaces with detergent and water, and dry completely. Wear at least a NIOSH Approved N95 respirator, gloves and goggles. People with asthma or weakened immune systems should not be there while it is being cleaned.

If you smell mold but can't find it: call a testing company

That's the classic hidden-mold case, and the EPA suggests you consider hiring an experienced professional. In Texas, a licensed mold testing company handles mold assessment, which TDLR defines as inspecting or surveying a structure to provide information about the presence of mold. See how to test for mold and mold testing cost.

If the mold is large or the damage is serious: call a removal company

For 25 contiguous square feet or more, flood damage, sewage or mold in the HVAC system, hire a licensed mold removal company. TDLR defines remediation as the removal, cleaning, sanitizing, or other treatment of mold or mold-contaminated matter. Our mold remediation process and mold remediation cost guides explain what to expect.

Keep the two jobs separate. Texas law says a license holder may not perform both mold assessment and mold remediation on the same project. Before you hire, confirm the license with our license check tool, and read how we verify every company.

Find licensed companies:

• Houston mold testing and Houston mold removal
• Dallas mold removal
• Fort Worth mold testing
• Austin mold testing
• El Paso mold removal
• All cities: Texas mold directory