Warning Signs: How to Tell If You Have Mold Behind the Walls


It’s the real-life monster that no one wants in their home. It’s the four-letter word that causes homeowners to scream in terror. It’s mold, and it’s a problem for many homeowners. For some people, indoor mold spores can cause symptoms ranging from sneezing and eye irritation to serious lung problems. The good news is that if detected early, mold can be safely removed before it becomes a catastrophe.

How do you know if it’s mold?

The bad news: Mold loves to hide. How do you find this evil house guest before it’s too late? Your nose knows.

Your sense of smell is the first line of defense against mold. You can often smell mold before you can see it. If you notice a musty smell in your home, there’s a good chance you have mold. If you think you have a mold problem, get on your hands and knees and smell the electrical outlets. As silly as it sounds, this is not a practical joke. Outlets have better access to the area behind walls, and smelling them can help pinpoint the mold problem. If mold is there, you’ll be able to smell it.

You should also investigate the areas in your home where mold loves to hide. Basements and bathrooms are likely places, but check out our infographic revealing the six secret places mold loves to hide: chimney, roof, windows, washing machines and under wallpaper.

If you’re still not sure, it’s time to call in a professional. Professionals can test the air for mold spores and determine if and exactly what type of mold is present.

Ready to get started on mold protection? Make sure you are doing it right.


Infographic: 6 Secret Place Mold Loves to Hide

So what do you do if you find mold?

If you do have mold, it’s important to tackle the problem quickly and safely.

Hire a professional to properly remove the mold and clean the area. Once you have ensured the source of moisture has been eliminated and everything is clean and dry, you can safely close up and refinish the affected area. When it comes to mold, too much precaution is just enough.

Of course, the best offense is a strong defense. Preventing the problem is key to a healthy home.  Keep your home well-ventilated and dry, and use mold resistant drywall and insulation.

Think it might be time to call in help? We maintain a database of professionals we trust and you can too.

 Link to CertainTeed's Find a Pro page

Plus, how to prevent mold growth after water damage and is it mold or is it mildew? We help you decide.



  1. Eli Richardson on

    Thanks for stating that musty odors in your house, is a sign of mold. My brother found a leak in his attic that was damaging his walls. I’ll let him know to call a professional mold removal because that the odors coming from the attic is due to mold.

  2. Charlotte Lyon on

    I’m having a mildew problem on my kitchen and living room walls. I’m desperate to find the source of the problem.

  3. Sharon Smith on

    It got me when you said that it’s possible that you have mold if you can smell musty odors in your house. With that in mind, I’ll be sure to hire a mold remediation company for help. Since last week, my son has been complaining about headaches and sneezing due to his allergies. Almost all parts of our house smell like a damp cloth which resembles the odors of mold. Thanks for sharing this.

  4. Nathan Carter on

    I found it interesting that you suggest smelling around an outlet to find if there is any mold behind. I have been smelling an interesting mustiness at my parents’ home the last couple weeks. I will keep this in mind, and see if I can find any mold, and look for mold removal services around me.

  5. Ellen Hughes on

    You got me when you said that it’s possible for mold to settle in if there are leaks on your roof. With that in mind, I’ll be sure to hire a mold remediation company as soon as possible. Our house has musty odors that have been causing my children’s allergies to get triggered. If I may share, we had our roof replaced because our old roof has a lot of bald spots that caused the water to leak in our house.

  6. I needed to leave a comment, man do I’ve a hard time writing
    a blog. Im endeavoring to kick start one on my website and I must
    its not easy at all. I really do admire people like yourself who are
    able to reveal anything with ease. Keep up the good work!

  7. Thanks for the recommendation about checking bathrooms and basements for mold. My mother’s house smells damp and musty, but I haven’t found any signs in any of the bathrooms. I forgot to check the basements, but I bet a mold removal service would find it down there.

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