Crawl Space Mold & Moisture Problems

We are moisture control contractors, not health professionals, so this page sticks to what we can speak to: why crawl spaces get damp, what that dampness does to a house, and how it is corrected. If you have health concerns about indoor air quality, those questions belong with a medical professional or an indoor air quality specialist.

Common causes of crawl space moisture

Exposed soil

Bare ground releases moisture into the crawl space continuously. This is the single largest source in most homes, and it is why a ground vapor barrier is such an effective first step.

Standing water

Water on the crawl space floor keeps everything above it damp. It has to be addressed with drainage and often a sump pump. See wet crawl space repair.

Condensation

When humid outdoor air enters a vented crawl space and meets cooler ductwork, plumbing or block walls, moisture condenses out of the air onto those surfaces. In North Carolina this happens for months at a time.

High humidity

Damp air alone is enough to keep wood moisture elevated even with no visible water. Once the space is sealed, a crawl space dehumidifier keeps humidity in a reasonable range.

Wood moisture

Joists, beams and subfloor absorb moisture from the air around them. Elevated wood moisture over long periods is what allows decay organisms and surface growth to take hold, and it eventually leads to structural repair.

Poor drainage

Downspouts discharging at the foundation, grading that slopes inward, and blocked drains all keep delivering water to the perimeter of the house.