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How To Find Mold in House (Even If It’s Hidden)

How To Find Mold in House

Hidden mold is a nuisance that can cause health issues(1), worry and fear for homeowners.

Plus, if it gets out of hand it can cost a lot to remediate.

Knowing how to find mold in house will save you a lot of problems. By the end of the guide, you’ll be learn the proper way to detect hidden mold growing throughout your house.

Mold can grow virtually anywhere, and it’s not always easy to detect its presence without an expert eye.

Today, we will discuss how you can tell if you have hidden mold growth lurking in your home even when it’s hidden from sight!

Often inspecting your home frequently and addressing all moisture problems is the key to controlling mold growth.

Finding Hidden Mold Before It’s Too Late

If you are a homeowner, you may already know that excessive moisture can promote mold growth that could cause allergic reactions in some individuals, as well as damage building components and personal items.

The key to controlling mold lies in eliminating the source of moisture and the conditions that promotes its growth.

Investigating a mold-related issue has many facets and can be a daunting task, especially for individuals who are not familiar with the inspection process.

Often, observing the appearance and pattern of mold growth on surfaces can provide pertinent information regarding the moisture source.

For instance, if you observe a linear growth pattern on ceiling areas, this could indicate condensation issue.

More specifically, the line to the AC unit in the attic could be sweating, resulting in water from the line dripping on the upper surface of the ceiling tiles.

Picture of mold growing on ceiling

In contrast, mold growing in a circular pattern on the surface of a ceiling usually indicates a leak centered in that location. When indoor humidity is an issue, the mold growth will be scattered and take the shape of droplets.

Picture of mold growth caused by high indoor humidity levels

Mold growing along baseboards of an exterior wall that has no plumbing could indicate a water intrusion issue.

Mold growth may also appear in the form of black conk-like structures on surfaces such as wallboard and drywall, if they are hidden behind cabinets or furniture.

These fungal accumulations may prevent them from being noticed at first glance; however, their presence is a good indicator that hidden mold has taken hold somewhere nearby.

Depending upon its location and extent of damage caused by hidden mold, it’s important to call an expert for assistance with remediation efforts.

This way you can ensure your home will be safe for years to come!

Areas In The House To Starting Detecting Mold (Mold Growth Love These Places)

  • Bathrooms: In or under cabinets, in the shower on grout lines, flooring area, on baseboards, behind toilets, the edge of bathtubs, and behind wallpaper.
  • Kitchens: In or under cabinets, behind the fridge, behind dishwashers, under garbage disposal, around drain and water supply lines.
  • HVAC Closets: Found on the walls in the HVAC closet, condensate disposal drain lines, on air filters, flooring, and duct board/liners in the return air plenum.
  • Laundry Rooms: behind the washing machine and on the flooring.
  • In basement areas: Mold growth is found frequently in home basements on walls and floors when flooding or water intrusion has occurred.

Important Tips When Inspecting For Mold Problems in your House

  • Are there any previous or existing moisture issues in the home? This is usually a good starting point. Focus on smells and pay special attention to any wet or damp areas.
  • Are musty odors present? Where?
  • Inspect areas for any discolorations, stains, or other signs of active mold growth.
  • Look for standing water or wet spots in moisture-prone areas such as under bathroom sinks, kitchens, mechanical rooms, and laundry rooms. Additionally, water can occasionally migrate into a garage or basement unnoticed. If any source of moisture is observed, act promptly to dry out the area and assess any damages.
  • Inspect clothes dryer, bathroom, and stove exhaust systems to ensure they vent to the exterior of the home.
  • Inspect walls and ceilings for any peeling or flaking wall coverings, bubbling paint, water stains, soft spots, or any other signs of water intrusion.
  • Have your roof inspected for missing shingles, the improper flashing around roof penetrations, and any rotting wood.
  • Check the heating, venting, and air conditioning (HVAC) equipment. Verify the drain pan has no standing water, check drain lines to ensure they are free from obstructions, coils are clean, and the air filter is replaced when necessary.
  • Check around the windows for signs of condensation or standing water.
  • The air conditioning system should be serviced as recommended by the manufacturer.
  • Test the humidity of the air indoors. The relative humidity (RH) should range between 30 to 50 percent. Humidity levels of 60 percent and above promote mold growth.

What To Do If You Find Mold in Your House

  • If you see mold growing, avoid touching the contaminated items with your bare hands- always use rubber gloves.
  • Always wear safety equipment such as gloves and goggles, and at a minimum, an N95 respirator- when necessary.
  • Do not attempt to disturb mold without first isolating the area to protect others in the home.
  • Avoid breathing in mold spores.
  • Avoid mold contact with eyes.
  • If the area involves gross contamination, consult a licensed mold remediation specialist.
  • If the mold growth is caused by sewer backup, flooding, or other contaminated water sources consult a remediation contractor. Contaminants like bacteria and viruses present on the materials

Mold growth is not always visible and easy to detect. Sometimes, mold could be growing on the back of drywall, wall coverings (wallpaper and panels), under carpeting, in air ducts, behind ceiling tiles, and in wall cavities.

Other possible locations include behind furniture, drapes, in attics, and crawlspaces.

Any location where moisture can accumulate by condensation, water intrusion, or plumbing leaks should be assessed thoroughly to uncover hidden mold growth.

Uncovering hidden mold can be difficult and sometimes require intrusive inspections.

DIY Methods To Find Hidden Mold Growth In The House

Below are methods that you can use to locate hidden mold growth areas without dispersing mold spores in the indoor environment.

The Three-Sided Inspection

  1. Use a box knife or other hand tool (not a power tool) to cut three sides of the suspected wall to create an opening (door) pictured below.
  2. Gently pry the door open from the top with a thin blade.
  3. Use a flashlight to inspect the backside of the wall.
  4. If mold is present, close the opening and place duct tape over the cut seams until the full extent of the problem can be determined.
  5. Keep the area sealed until you can have the area inspected to determine how the extent of the mold infestation.

Bore Scope Inspection in Wall and Ceiling Areas

  1. In suspect areas where leaks have occurred, this method is an effective way to inspect wall and ceiling cavities that may have mold growth.
  2. Locate the suspect area. These areas could show signs of damages such as staining or discoloration, rusting nails protruding from walls, signs of peeling paint, soft area, bubbling, and other indicators of water damage.
  3. Use a drill or other method to gently create a small diameter hole about the size of a dime.
  4. Insert the scope and look for signs of mold growth.
  5. If mold is present, place a piece of duct tape over the hole and keep the area sealed until you can have the area inspected to determine how the extent of the mold infestation.
  6. Remove and clean scope once the cavity has been inspected

Inspecting Under Carpets And Padding For Mold

This method is simple and easy, providing you have a few tools handy.

This process is used to determine if there is mold growing on the carpet, padding, or the tack strips used to secure the carpet in place.

See If the carpet smells musty, feels damp, or the baseboards have water damage. Wear leather gloves to avoid injuries from the nails on the tack strips.

Mold growth and water damage under carpet
  1. Select the area of the carpet that is suspected of having issues.
  2. Inspect the top of the carpet for any signs of mold growth – this will be hard to observe on dark colored carpets.
  3. Gently use a pair of pliers to pull the edge of the carpet from the tack strips.
  4. Slowly lift the carpet and padding to inspect the back and the tacks strip for signs of mold growth.
  5. If mold is present, lay the carpet back in place and lay a sheet of poly or plastic sheathing over the area to keep the affected it isolated. Then contact a contractor to determine the extent of the mold growth. In most cases, the carpet with mold is removed and replaced.

Inspecting Behind Furniture And Household Items For Mold Growth

Often, mold growth can be hidden by the furniture placed against the walls in your home.

When inspecting your home, it’s important to look behind bookshelves, headboards, dressers, pictures, desks, and sofas for any signs of mold growth.

Mold Growing behind a storage container

When the mold growth cannot be located, it’s always best to consult a qualified mold assessor or specialist.

Homeowners who opt to perform mold cleanup in their homes should be diligent in taking safety precautions that protect the occupants from any potential exposure to mold.

If you have more than 10 square feet or microbial growth caused by sewer or contaminated waters, you should contact a remediation firm to have an assessment completed and the correct steps performed.

Attempting to address these conditions could cause further contamination and potential health issues. The firm selected should be licensed and insured to remediate contaminated water, microbial growth, and perform remedial work.


Hidden mold growth in your home can be discovered by using a variety of methods, including the bore scope inspection in wall and ceiling areas, inspecting under carpets and padding, or inspecting behind furniture and household items.

Now you know how to find mold in the house, use this knowledge to locate it before it spreads even more.

If you suspect that hidden mold is growing somewhere within your home but cannot find it, call an expert to perform an assessment so they can determine how to address the issue.

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