The Negative Effects of a Wet Crawl Space


Air flows upwards throughout your home from your crawl space, bringing the humidity with it. This humid airflow can have several effects on your home, which you may not associate with your crawl space, including:

1. Dust mites

Dust mites are the number one indoor allergen. They thrive in warm, humid environments and are commonly found in bedding, furniture, and carpets. These microscopic creatures trigger allergic reactions and asthma symptoms, such as sneezing, runny nose, and itchy eyes.

2. Sticking Doors and Windows

A humid crawl space can cause doors and windows to stick due to the increased moisture content in the air, which gets absorbed by wooden structures. Wood naturally absorbs and releases moisture based on the surrounding environment. When humidity levels rise, wood swells as it takes in moisture, leading to an expansion in size. This expansion can cause doors and windows to become too tight in their frames, making them difficult to open or close. Persistent high humidity can make this issue worse, potentially warping the wood and causing long-term damage. 

3. Smelly Damp Carpets

Since moist air rises, the overall humidity of the home increases. This moisture is absorbed by carpets upstairs, promoting mold and mildew growth, which can result in musty odors and potential health risks. Proper encapsulation or dehumidification of the crawl space is essential to prevent this problem and maintain a dry indoor environment.

4. Buckling Hardwood Floors

With excess moisture from the crawl space seeping through the subfloor, the wood absorbs the moisture and begins to expand. This expansion makes the planks push against each other and the walls, leading to noticeable warping. Over time, this can permanently damage the flooring, requiring expensive repairs or replacement.

5. Condensation or Mold on the Inside of Windows

You may notice water droplets form on windows, with moist air rising from the crawl space and condensing on cooler window surfaces. This moisture fosters mold growth on sills and frames, damaging windows and posing health risks.

6. Increased Heating Bills

High humidity in a home makes it harder to maintain a comfortable indoor temperature. Since moist air is more difficult to heat, the heating system in the home has to work harder and run longer. Additionally, excess moisture can can actually lead to heat loss, since moisture negatively impacts the insulation of the home.

7. Increased Cooling Bills

Like heating, moist air is difficult to cool down, putting additional strain on the home's air conditioning system, decreasing its efficiency, lifespan, and increasing the home's cooling bills in the process.

8. Mold Upstairs

Moist air from a crawl space increases the overall indoor moisture levels. Moist air from the crawl space rises and settles in living areas, creating damp environments and promoting mold growth. Mold spores thrive on organic surfaces like walls, ceilings, and furniture when there's excess humidity.

9. Decreased Life of Paint on the Outside of the House

Moisture from a crawl space creates an overall damp environment in the home. The exterior paint of the home can crack, peel, and blister from any humidity permeating through the walls. This also effects the protective function of the paint, making the exterior more susceptible to weather damage. 

10. Aggravated Asthma and Allergies

Mold spores and dust mites are common allergens that can trigger allergies when inhaled. The increased moisture from a crawl space provides an ideal environment for these allergens to thrive, worsening the indoor air quality.


As the air rises from your crawl space, it carries moisture and affects various parts of your home. From mold growth to increased energy bills, even sticking doors and smelly carpets, the air of your crawl space has a direct effect on the air quality of your home. Controlling the moisture in your crawl space and throughout your home is essential for both the structural integrity and indoor air quality of your home.


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