When my husband and I bought our current home in upstate New York, our plan had been to spend the bulk of our renovation budget on a new kitchen and the main living spaces, and to just paint and spruce up the bedrooms. But a persistent dank, musty smell in the would-be bedrooms forced us to reallocate our funds. That smell turned out to be mold, and the only way to get rid of it was to take the walls down to the studs and rebuild.

Our new kitchen would have to wait.

Chris McLaughlin, sales manager for JES Foundation Repair, a company that works on foundations, crawl spaces and basements in the Washington, D.C., area, says that musty, dank smell is usually the first clue that you have a mold problem.

“The thing is, most people don’t even realize there is a problem. They grew up with a moldy smell in their basement or closets, and they never really knew what it was or thought to do anything about it,” McLaughlin said. “But one day, someone comes in to do some work, and they start opening up drywall, and they find mold all over the place.”

The Centers for Disease Control and Prevention advises that if you smell or see mold, you need to remove it as soon as possible as it can pose a health risk. And once it’s removed, you should hire a professional to deal with fixing the environment (moisture and humidity) that is conducive to the mold growth.

Georgetown University Medical Center’s Richard A. Calderone, a professor and the chair of the Department of Microbiology and Immunology, and Joseph A. Bellanti, a professor of pediatrics and immunology, explained in an email that people exposed to mold-filled buildings are more likely to suffer from mild respiratory symptoms (such as sneezing, runny nose and itchy eyes), asthma, hypersensitivity pneumonitis (a rare inflammatory lung disease), respiratory infections, hay fever, bronchitis and eczema — illnesses that none of us want to deal with, especially during the coronavirus pandemic.

A contractor removes insulation and shows damage caused by water infiltrating the outer stucco layer of a house and deteriorating the wood structure beneath. The back side of interior wallboard that has been affected by mold.
A contractor removes insulation and shows damage caused by water infiltrating the outer stucco layer of a house and deteriorating the wood structure beneath. The back side of interior wallboard that has been affected by mold.

Mold can be difficult to identify, because you don’t have to see it for it to be present. Beyond the musty, rotten smell, other signs to watch for are greenish black spots, water-stained building materials, or excessive water damage. Mold is most commonly found in basements and crawl spaces, where humidity and dampness are highest.

To combat mold, experts recommend keeping moisture in your home at levels below 60 percent by using dehumidifiers and running your air conditioner. (The CDC recommends levels between 30% and 50%.)

It’s best to use air-conditioning units with high-efficiency particulate air (HEPA) filter attachments, because they will trap mold spores and prevent mold accumulation; make sure you replace the filters twice a year. Also, keep your air-conditioning drip pans and drain lines clean, using either distilled vinegar or a product formulated for this purpose, available at many home-improvement stores. Make sure that your ductwork does not sweat. Look for white residue that is left on the bottom edges of ducts, where the water drips onto the surface below.

If you live in a very humid climate (daily levels at or above 60%), Calderone and Bellanti recommend choosing linoleum, hardwood or ceramic flooring instead of potentially moisture-retaining, wall-to-wall carpet. They also suggest cleaning hard surfaces such as glass, plastic or tile, which can be breeding sites for mold, with a bleach solution, soap and water, or a commercial product. You should clean them immediately if you see mold, but these surfaces (most often in bathrooms and kitchens) should be cleaned weekly to prevent mold growth.

In the bathroom, Calderone and Bellanti say to always use an exhaust fan or an open window to cut down on humidity. In the kitchen, keep a lookout for mold in refrigerator drip pans, door seals and garbage pails. Whatever you do, McLaughlin says, never paint or caulk over mold; remove it, instead.

Precautions you can take outdoors to prevent mold growth include moving outdoor sprinklers away from your home, cleaning gutters and directing all water flow away from walls. Also, promptly fix leaky roofs, windows and pipes. If you live in an area that is susceptible to high rains or flooding, McLaughlin recommends installing a sump pump.

If you do discover mold in your home, realize that unless you address the underlying issue — moisture — mold will probably return. “If you fix the moisture problem, you fix the mold problem,” McLaughlin said.