How to Get Rid of Mold in Dirt Crawl Spaces

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The discovery of mold in a home often strikes panic in the residents. However, mold is more common than you may think. It enjoys a comfortable, moist environment, making a crawl space an ideal place where the microscopic spores can settle down and flourish. Not all mold is the same, although all mold should be addressed and removed. Know what type of mold you have before digging around in a dirt crawl space.


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Types of Household Mold

There are many types of mold that can be found in the home. While you will want to get rid of any mold that is growing in your crawl space, knowing the type of mold will help you to discern the best way to deal with it.

Yellow mold is fairly common, but it can be destructive to the materials in the crawl space. The ​serpula lacrymans​ type of mold is also known as house-eating mold. It eats away at the wood material inside a crawl space. You can find yellow mold on the soil of houseplants or in other dirt imports that come into your home.


Aspergilius is commonly found in the home and isn't harmful to healthy adults. Small children and those with weaker immune systems can suffer some respiratory issues if they breathe in aspergilius over a long period of time. However, the Center for Disease Control recognizes aspergilius as an unavoidable airborne fungus.

Dangerous Mold in Crawl Spaces

The dangers of mold in a crawl space can include respiratory issues and other ailments. There are a few molds that are more serious to be around than others. These include:


  • Alternaria​ is a common allergenic mold that can cause wheezing, coughing, sneezing or other breathing problems.

  • Cladosporium​ is a potent fungus that can quickly cause serious respiratory issues for children, seniors or those with asthma. This black, creeping mold can thrive on barely damp dirt and wood, on cloth material, inside HVAC systems, on painted walls, in mattresses and on food and paper.

  • Stachybotrys​ is the mold you don't want to find. It is the most toxic of the molds that can grow in a crawl space. This is the true "black mold" that is dangerous to all who have the unfortunate luck to find it growing in the dirt, drywall, carpet, subflooring or insulation. For this type of mold, you may want to hire a professional so you don't inadvertently spread the mold into other areas of the home.


Humidity and Mold

The humidity level in a home is important for many reasons. It's not just about comfort. Humidity levels greatly affect mold growth in crawl spaces. If it is too high, it can lead to the ​rapid expansion of fungus and mold​.

The crawl space can become moldy or a musty odor may take root in the framing wood or drywall in a cramped crawl space. It can attract a host of fungi that will take advantage of the conditions and spread quickly before you can notice.


Ideal Humidity for Each Room

The humidity levels in each room can contribute to issues in the crawl space. Monitor the humidity level in each room to keep the moisture under control and mold at bay in the hidden spaces beneath your home and within the walls.

A home's humidity levels in the winter should be around ​35 percent​. In the summer, the humidity level can increase to around ​45 percent​. Different climates may have different levels of humidity.


A bedroom's humidity should be slightly higher to keep the air moist enough to reduce itchy throats or dry skin. The bathroom's humidity can be as high as 50 percent, but anything higher puts the space in danger of attracting growths of mold, mildew and/or fungi. The living room humidity level should be around 30 percent.

Precautions to Take Before Mold Removal

Cleaning a crawl space of mold is a physical job. It requires a lot of scrubbing in tight spaces. Having safety measures in place before you begin will ensure you get the best job done as quickly as possible and without any unwanted trips to the emergency room.


Use gloves with a textured-grip material on the palms and fingertips when handling slippery tools. This will cut down on blisters or lacerations as you work in rough areas.

If you are using strong commercial cleaners o homemade cleaners that have ammonia or bleach as a base, then you will want to cover your mouth and eyes. The chemicals can build up in the small crawl space and overwhelm you. Wear a dust mask or chemical mask as well as protective eyewear that wraps around your eyes.


Hiring a Professional

Experts agree that mold removal can be a ​complex and lengthy process​ for amateurs. If you are in any way unsure about cleaning out mold from your home, have asthma or other respiratory ailment or young children in the home, then you may want to seriously consider hiring a professional.


A ​mold specialist​ can ensure that:

  • The spores don't spread and you aren't inconvenienced as they work to rid the home of problem mold.
  • Any leftover mold you didn't clean up doesn't quickly return and take over, sometimes stronger than before.
  • A qualified mold expert will assess the level of mold, the best way to remove it and have the proper equipment and permits.


To find an expert, check with the Better Business Bureau and contractor's board to ensure that the mold expert you hire is properly licensed. If you continue to get a whiff of mold or mildew, it is time to hire an expert to locate the source.

How to Safely Remove Mold

After you have donned safety glasses, gloves, and a mask, the first step is to tackle the large pieces of mold, mushrooms, swaths of mildew and other large pieces.

Use the flat end of a shovel or large putty knife to get cleanly between the dirt floor and the unwanted growth. Get it as clean as possible before applying any cleaners.

Cleaners for Mold Removal

Using an acid-based cleaner such as vinegar can ensure any mold you may have missed in the dirt won't grow back. Douse the vinegar onto the dirt floor with a pump sprayer. The vinegar will evaporate after removing up to ​90 percent of fungus​ in the crawl space that you may have initially missed.

A commercial cleaner can make quick work of eliminating mold from tight spaces that are difficult to reach. Always read the manufacturer's instructions before applying the product to the dirt floor, cement walls or wood structure.

Final Mold Removal Measures

If you can maneuver a UV lamp into the space, flood the dirt floor for 24 hours with the light. This will kill off the last spores that are clinging to areas you may have missed. This has the added benefit of removing bits of moisture from the dirt floor from the vinegar or cleaner.

Finally, direct fans through the crawl space to circulate the air and rid it of any lingering odors that can drift up into the rooms of the house.

How to Prevent the Return of Mold

You don't need standing water to run into mold and other unwanted growths in your crawl space. Moisture from weather, small leaks or condensation can create just enough moisture to make an inviting environment for mold or fungus in a crawl space.

If you have a vented crawl space, make sure that the insulation is secure to the subfloor and the vapor barrier side is facing the heat source. Lay down polyethylene plastic or a quality roofing paper to add a layer of protection to the crawl space floor. A crawl space should have a minimum of one square foot of ventilation every 150 square feet.

Mold in Old Joint Compound

If you have put away joint compound for patches in the crawl space and find mold forming on the surface, then you may worry about whether it is still effective. It should work just as well as the last time you used it. Simply scrape the mold off the top. Wash the compound once it is set with a solution of diluted bleach if you are worried about mold popping up from the mixture.



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