The Mold Coating Myth

Can I use coatings ‘to seal in’ mold spores?

The short answer is no. Even the top-of-the-line products often recommended by contractors will not ‘seal in’ mold spores or other toxins. If you have a mold problem, coatings are just one piece of the solution. Adding a coating on top of existing mold is like getting a flu shot when you already have the flu; it doesn’t help and can actually cause more damage. 

After water damage has occurred, wood and other porous materials need to breathe and dry out completely to stop the growth of mold and prevent recurrences. Applying a coating over moist materials and mold spores only locks the moisture in, creating a perfect environment for mold to flourish beneath the coating.

How to properly use coatings

Coatings do not provide a barrier to mold spores or their toxic by-product: mycotoxins. Though you no longer see the mold, it may still be there, contaminating the air and damaging your health and the health of your family. Even the companies that make mold and mildew resistant coatings, which are often suggested by contractors, do not recommend applying coatings over existing mold. Always read the fine print on manufacturers’ labels.

Watch the video below to understand more about mold coating products:

What should I do instead of using coatings to seal in mold?

The only way to fully eliminate mold and the associated health risks is to completely clean and remove all existing mold, allow materials to dry to a normal moisture content and correct the reason the moisture was a problem in the first place. If the conditions that caused the mold to grow continue after cleaning, the mold will just grow back. And your money spent on cleaning will have been wasted.

To ensure materials are adequately dried before any restoration work or coatings are applied, you’ll need a moisture measuring probe to test the moisture content of materials. 

Use a moisture meter to test moisture levels

Even when wood, insulation and drywall seem dry to the touch, inner layers can still retain moisture, creating a perfect environment for hidden mold. Use a measuring probe to measure moisture on external surfaces and a deep testing probe for internal surfaces. 

When water has traveled and settled, it may be necessary to test deep into materials. In some cases, a 2-inch or longer probe can be used to check moisture content beyond the surface. A qualified professional will have this type of equipment. Always check before you hire! A surface moisture meter is affordable enough for homeowners to do their own screening, but keep in mind that these only test close to the surface of materials.

Eliminating mold requires regular monitoring and attention to detail

Once moisture levels have returned to normal, you can add paint, sealant or other coatings to guard against future mold and mildew growth. But the most important preventative measure is to stop the moisture. There is no product that will guarantee materials will stay mold-free if the material is exposed to moisture again.

The moisture content level defined as “normal” varies by material and climate. However, there are guidelines to follow: drywall should be under 3%; wood should be under 10%; indoors and under 15% outdoors; tile will vary, so look for typical levels and then check for anomalies or variations to discover undue wetness.

What else do I need to know about using coatings to seal in mold?

When finishes are applied, keep in mind that the new finish, itself, is the only thing protected from mold growth. Everything underneath is still susceptible to mold. To truly seal out mold, a material must be encapsulated on all sides. Make sure the moisture problem is fixed, or the mold will just grow back! 

You may want to seek the help of an experienced consultant or professional mold remediation specialist familiar with the American National Standards Institute’s Reference Guide for Professional Mold Remediation

Always do your own research, regardless of who you hire. It’s your health at stake! Read product labels, including the fine print and warranties, to find the facts before using any mold-resistant product.

➡️ How to clean mold safely if you already have it!

Cheryl Ciecko is an ALA, LEED AP, Licensed Architect who helps homeowners and building professionals create safe homes through online education to prevent mold, water damage, and poor indoor air quality. 


You can find her video masterclasses, online programs, and education subscription options at .


For detailed answers on your specific situation or building project, schedule your appointment for an individual consultation.




The information contained in this presentation is for educational purposes only and is not intended to diagnose, prescribe, treat, or cure any disease, ailment or injury to the body. It is not medical advice. FDA regulations prohibit the use of medical claims in conjunction with the sale of any product not approved by the FDA. Statements made herein have not been evaluated by the FDA. 

Any products, techniques, and/or personal usage tips referred to are not suggested as a replacement for proper treatment from a licensed health care professional. I am not a licensed health care professional and the decision to use or not to use any of this information is the sole responsibility of the listener and/or reader. Everyone is an individual with different body types, different blood types, different body chemistries, and it is important to remember that what works for one person may not work for another person.