How to Tell if You Have Mold Behind Your Drywall

David J. Allen

I spent the better part of 2 ½ years learning about mold and indoor air quality because my child's life depended on it. Now I help others avoid ever having to experience the same thing. The mold industry suffers from conflicting opinions and I do my best to distill loads of data into something practical and useful. I love hearing from and helping readers. • "A house desecrated by mildew, mold, or fungus would be a defiled place to live in, so drastic measures had to be taken." — Leviticus 14:45

As unpleasant as it is to consider, you may have mold growing behind your walls without even realizing it’s there. Like most funguses, mold requires a moist environment to flourish.

Common household issues like leaking pipes, damaged roofing, and cracked ductwork can all potentially lead to its arrival and rapid growth. If mold is allowed to spread unchecked behind your drywall, it can result in health hazards and structural damage to your home. However, if you know what symptoms to look for, you’ll have a good shot at catching and treating the mold infestation before it causes major problems.

Wall Stains and Discoloration

In most cases, mold growing behind your walls will be caused by water damage; moisture stains materializing on your walls are another common symptom that tends to accompany that water damage. These stains will typically be tinted yellow or brown, and any time you see one, there’s a good chance that mold spores are lingering behind it.

Alternatively, there may be other discoloration on your walls coming directly from the mold within. In this case, the colors you see can range anywhere from black, to green, to white. Even pink or purple stains are likely an indicator of mold growth; the nasty fungus can develop in practically any color you can imagine.

Wall Deterioration

If you’re checking your home for signs of mold growth, check for any surface changes or deterioration on your walls. When the harmful fungus is spreading behind your drywall, it will frequently cause the paint to crack, peel, or grow bubbles. In some serious cases, the presence of moisture can lead to the walls themselves becoming warped or even bulging. Seeing any of these occurrences is an instant red flag and a likely indicator of an expanding mold problem.

Musty Odor

Mold is notorious for producing a distinct, musty smell. Although it’s a unique odor, the closest comparison might be the earthy smell of wet soil, like you might notice while walking through a forest after a rainstorm. However, it’s not nearly as pleasant. If you’re noticing this offputting smell in your home and you can’t deduce where it’s coming from, it could be mold behind your drywall. It may be awkward to check, but if the odor is significantly stronger coming through your electrical outlets, that’s usually a sure indicator that there are mold spores back there. 

Physical Health Symptoms

Breathing in mold spores regularly can be very detrimental to your health, and if the fungus is growing behind your walls, you may not even know that you’re doing it. If you start experiencing one or more of the following symptoms for no apparent reason, it could be a result of an unseen mold issue.

  • You seem to feel better physically when you’re out of the house than when you’re at home
  • Itchy eyes and nose
  • Frequent sneezing
  • Trouble breathing or scratchy throat

Before you assume the mold growth is behind your drywall, be sure to inspect the basement, attic, and any other parts of your home that could be humid or moist.

How to Handle Mold Behind Your Drywall

If you’ve managed to deduce or have a strong suspicion that there’s a mold infestation lurking behind your drywall, immediately contact a reputable mold remediation company in your area. They’ll be able to diagnose the problem, contain the mold growth, and safely remove the spores.