Here’s How to Prevent Moisture Buildup in Your Crawl Space (2024)

Improving foundation ventilation to prevent moisture buildup is a critical part of crawl space maintenance for Dallas homeowners.

Moisture in the crawl space can compromise foundation health and impact your home’s structural integrity. It can also create mold and mildew that impede indoor air quality, aggravate allergies and asthma, and cause respiratory issues.

This guide explores what causes crawl space moisture. And if you’re savvy with DIY home improvement, it offers some steps you can take to ensure good crawl space ventilation.

What Causes Crawl Space Moisture?

The Dallas-Fort Worth climate is humid subtropical with hot summers. The region also gets its share of torrential downpours. Over 28 inches of rain in DFW from January 1 through June 5 makes 2024 the fifth wettest year to date.

Rising groundwater from heavy rains can flood your crawl space if you have drainage issues due to clogged or insufficient gutters and downspouts.

Water or moisture can also enter the crawl space due to these concerns:

• Foundation cracks
• Leaking or bursting pipes
• Landscape sloping toward the foundation
• Groundwater seeping into the soil
• A sump pump malfunction
• A clogged sewage line

Moisture in the crawl space can rot wooden supports and jeopardize your home’s structural integrity. In addition, mold and mildew growth in wet and damp areas can also cause health issues. The moist, dark environment can also attract unwanted pests.

DIY Crawl Space Ventilation Improvements

A foundation repair expert can address cracks and other crawl space concerns. Here are some DIY crawl space ventilation techniques you can use to improve air quality and help keep moisture at bay.

Install Vents

Installing vents is one way to improve foundation ventilation and combat moisture. When you do this, you must follow the International Residential Code requirements for installing crawl space vents.

Place vents so they provide cross-ventilation. This means installing intake vents to pull fresh air in from outside and exhaust vents to manage interior moisture in the crawl space. Use one exhaust vent for every intake vent you insert. Also, install vents on opposite sides of the crawl space to help ensure good airflow.

Section R408 of the IRC code lists requirements for ventilating under-floor spaces (crawl spaces). R408.1 mandates that “the minimum net area of ventilation opening must not be less than 1 square foot for each 150 square feet of under-floor space area.”

This means if you have a 1,500-foot crawl space, you must have 150 square feet of vents.

To calculate the number of vents you need:

1. Measure the length and width of the crawl space and multiply those two measurements to determine the total square footage of the area.
2. Divide that total area by 150 to get the number of vents you need. (For example, 1,500 sq. ft./150 = 10 vents).
3. Round your answer up to the nearest whole number. It’s best to have more vents than not enough.
4. After you calculate the number of vents you need, place one every 30 feet along the crawl space.

If you’re unsure about how and where to place vents, you can always call a professional.

Install Exhaust Fans and Dehumidifiers

Installing exhaust fans helps draw moisture out of the crawl space. You should place the fan to send moist crawl space air outside. Adding a dehumidifier can bolster your crawl space ventilation system by removing moisture and keeping the air dry. If you use a humidistat, it automatically prompts the dehumidifier to turn on if the moisture level in the air reaches a certain level, which is another way to ensure the crawl space stays dry.

Install a Vapor Barrier

A vapor barrier slows the rate of ground moisture seepage into a crawl space. It generally contains 10-20 millimeter thick plastic sheeting that you overlap at least 12 inches across the floor and seal the seams with waterproof seam tape.

Also, bring the sheeting about 6 inches up the foundation walls and secure it with rubberized butyl tape. A puncture-resistant, single-layer vapor barrier works best.

Additional Moisture Prevention Tips

Beyond ventilation, take these additional steps to prevent moisture buildup in your crawl space:

• Fix any plumbing leaks.
• Keep gutters and downspouts clear and in good condition.
• Slope landscape to direct water flow away from the foundation.
• Repair any cracks or defects in the foundation.
• Install a sump pump.

Each of these measures helps keep moisture, mildew, mold, and unwanted rodents, insects, and pests out of your crawl space.

Furthermore, a dry crawl space protects the support beams upon which your home rests,

helping secure its structural integrity. It also prevents mold and mildew, which can hinder air quality and cause health issues for anyone who lives in your home.

Ecoscape is Here to Address Crawl Space Concerns

Ecoscape Foundation & Repair Services has proudly served customers in the Dallas-Fort Worth area since 1995. Our dedicated, knowledgeable team of foundation repair experts is ready and able to diagnose and resolve your crawl space ventilation or foundation concerns.

Contact Ecoscape at (972) 210-1494 to schedule a no-obligation consultation today!

This article was created by an external contributor. Members of The Dallas Morning News editorial and news staff were not involved in the creation of this content.