No Bleach for Cleaning Mold!

NO BLEACH For Cleaning Porous Materials – Including Wood!

I noticed an error in advice from the American Wood Council (AWC) regarding mold and mildew on structural wood members, in the FAQ section. It seems there are many, very reputable sources on the internet with poor information related to the cleaning of porous materials such as drywall, wood, brick, concrete, stone, and fabrics. Yes, brick and concrete are very porous and can grow mold. In fact, many materials are prone to mold growth if water is not managed properly.

Bleach should NOT be used on concrete.
Concrete IS a porous material.

WHY bleach should not be used

Bleach is never recommended for use in cleaning mold off of porous materials such as wood. It actually leads to an increase in mold spores. While the bleach evaporates, the water soaks into the wood fueling more and deeper mold growth.

Bleach labels warn that chlorine bleach will only be effective on a “hard, non-porous surface.’’ This means that the chlorine bleach component (10% vs. 90% water) does not “soak in.” Therefore, its disinfecting properties are limited to a hard surface like tile or glass. Commercially sold bleach contains 90% water, and mold loves water.

When bleach is applied, the chlorine quickly evaporates, leaving behind a lot of water. This water soaks into the porous surface, fueling mold to re-grow in the newly re-moistened environment. Therefore, using bleach actually feeds the internal mold spores! While the surface may look clean, the remaining spores will root deeper, stronger and will often return worse than before.

Bleach and mold facts:

  • Bleach ma encourage toxic mold to grow where it was not previously present.
  • Bleach may remove mold stains, however, despite a clean appearing surface, internal roots will continue to grow.
  • OSHA and the EPA have specifically advised against the use of bleach for mold remediation. See link below*
  • Chlorine bleach is caustic and extremely harmful to wood and many other surfaces. Bleach can weaken and break down the wood fibers and ultimately create further structural problems.
  • Bleach is dangerous! Mixed with ammonia, bleach creates a deadly mustard gas… one of the most lethal of all the poisonous chemicals used in WWI. NOTE: Urine contains ammonia – Using bleach in the toilet could create a toxic gas!
  • Bleach is a toxic chemical, classified the same as gasoline.
  • In its gaseous form (room temperature) chlorine bleach releases Dioxins, a known carcinogen.
  • Bleach is highly corrosive to bare skin, creating a hydrolysis reaction. The “oily” feeling of bleach on bare skin is actually the top layer of skin beginning to dissolve!
  • Bleach is hazardous to your health AND is likely to make your mold problem worse in the long run.
Bleach is a toxic chemical.

Please note

It should be noted that the Environmental Protection Agency (EPA)* and the Occupational Safety and Health Administration (OSHA)* have changed their recommendations over the years (although they have done very little to share or highlight the change).

* OSHA Reference

*EPA Reference

How to properly deal with mold

Mold is becoming an increasingly large problem in both new and existing buildings. I appreciate sharing AWC resources often, however, credibility gets questioned when misinformation is apparent. Hopefully these references will be corrected ASAP. I have let my contacts there know.

You can find more free information available on this website. Reducing or eliminating mold exposure is critical. It is important to know that often, mold is completely concealed and there are no signs other than health effects. Thorough visual inspections are necessary, along with other tests, which can be done even by educated building owners.

Essential oils are one of the protocols that I use to eradicate mold. If you would like to try essential oils to see for yourself what benefits are available, I am happy to help answer you questions. Contact me to request assistance with inspecting for mold and using proper remediation techniques.

Get your questions answered!

Cheryl Ciecko, AIA, ALA, LEED AP, is a 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.


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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.