Crawl Space Moisture: How to Control and Solve the Problem

Moisture build-up in basements or crawl spaces can cause significant damage to a home that is often very expensive to fix. If a water leak, condensation or high humidity is present and left untreated, mold and mildew will develop. Aside from potentially ruining household goods, moisture in the basement or crawl space can cause wood floors to warp and over time will rot the wood skeleton of a home and compromise the integrity of the structure.

If you have noticed an increase in the moisture content of the air in your basement or crawl space or notice condensation on the walls or floor, there are steps you should take immediately to avoid water damage. First, attempt to identify the origin of the water. Many times a plumbing leak is the cause of excess moisture in the basement. Check for leaks around water heaters, water intakes, and drain pipes. These leaks are often easy to fix, but do not hesitate to contact a plumbing professional for assistance.

If you are unable to identify a visible water leak within the basement, the water is likely to be infiltrating from outside the house. Rainwater must flow off the roof and away from the foundation of the home. To ensure this happens, check that the ground around the foundation of your home slopes away a minimum of ½” per foot. It is also important to properly divert rainwater run-off away from the foundation and into the yard by installing downspout extenders. It is also a good idea to check your exterior air conditioner or HVAC condensers to ensure the drain pipes are not clogged on these units. These pipes should extend far enough to keep this excess water from reaching the foundation. These steps should be taken to ultimately prevent standing water against the house which can seep into the basement or crawl space.

Physically crawl into the crawl space to inspect it. The soil here may be moist, and that is normal. There should not be standing water and the dirt should not be saturated. To greatly reduce the humidity in the basement, add a vapor barrier by covering the entire dirt area in thick, black plastic (6 mil or higher) that is available at any large home improvement store. Once leaks have been stopped, drainage issues outside have been addressed, and plastic is installed, consider renting or purchasing a dehumidifier to remove excess moisture in the crawl space or basement. If the source of the moisture accumulation has been properly dealt with, the water problem will not return and the areas under your house will stay dry for years to come.