Can’t Find Mold… Cut Holes?

Cutting a hole in drywall

Cutting holes is serious business when searching for mold in your home. It’s actually the last resort solution! Proper steps should always be followed before holes are cut as there are potentially serious implications. When you cannot find any mold through testing or visual inspection these are the next steps: 

Step #1: Check humidity levels – room by room. Look for anomalies and variations. The normal levels are listed below.

  • Cooling Season Level: Less than 60% 
  • Heating Season Level: Less than 40% 

Step #2: Hire someone to do a scan with a thermal camera looking for temperature variations. 

Step #3: Hire someone to use penetrating probe type moisture meters (several inches minimum).  

Step #4: Hire someone to air test inside of wall cavities 

Step #5: Get second/third opinions from other specialists.

Do NOT cut holes or otherwise disturb the structure looking for mold without proper precautions! 

Last Resort Solutions

Cutting Holes and Proper Precautions

If you determine you sense mold in a certain area or other indications suggest water damage, it often makes sense to cut open a surface to look further. 


Proper protections MUST be in place when doing ANY destructive testing, as it is possible you will find mold. The act of cutting and removing or other disrupting any building materials can cause additional mold spores to be released into the air, often in very large quantities. Health compromised individuals can become much sicker if exposed to newly release mold spores. Even those with no previous sensitivities can have significant reactions and become hyper-sensitive when they were not previously.

Use proper safety precautions when cutting holes

Proper Precautions include the following steps:

Step #1: Provide a sealed plastic enclosure with vestibule/air lock for entry and exiting. A ‘zipper door’ is commonly used for access. No air should be shared between inside and outside of the enclosure. 

Step #2: Block off all heating and cooling vent openings and seal tightly. Make sure to turn off other HVAC system while work is being done and for several hours afterwards. NOTE: Make sure there is enough intake air provided before turning the HVAC back on. (Contact the furnace manufacturer when in doubt.) 

Step #3: Creation of negative air pressure – Blow air out of the space using a HEPA quality air scrubber VENTED OUT through a window or door inside in the enclosure. NEVER EXHAUST Air scubbers into another part of the living space!!!Hire someone to do a scan with a thermal camera looking for temperature variations. 

Step #4: Plan for contaminated materials removal safely. A second window or door access to the outside is ideal. Otherwise, double bag materials inside the enclosure to be removed by handing to a unexposed person outside of the enclosure, who can bag the items again. A clean drop cloth covered path should be provided for exiting the structure. 

Step #5: Workers should be wearing removable protective suits and respirators that they can remove and bag in the vestibule before exiting through a living space. 

Step #6: Plan for how (route, bagged materials, removal through windows or doors) contaminated materials, equipment and people working will enter and exit the space safely. 

What to Remove

Remove a large enough area to view completely the entire assembly. This also often means removal of insulation that may be covering mold but appear unaffected. Concealed mold is often found on exterior wall sheathing, behind the insulation. Sixteen inches square or more may be considered. Make cuts with ease of repair in mind. Often bigger is better and not more expensive.

Where to cut a hole

Make your best guess to open an area where any smells, color or texture changes are evidentConsider locations below any exterior wall penetrations, including windows, doors, balconies or decks, porch roof overhangs, vent outlets, hose bibs, etc.

Holes cut in shower tiles

Important Considerations

  • WATER TRAVELS and mold may not be at the original leak source.

Keep Learning How To Deal With Mold Safely

First Steps When You Find Mold

Learn even more in my video masterclass “First Steps To Remove Mold”!

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.