Is Radon Lurking in Your Crawl Space?

Vapor Barrier

Many homes and buildings across the U.S. have crawlspaces with radon gas problems. Radon makes its way into the crawlspace from the ground underneath. Crawlspaces with exposed soil floors have no barrier to slow down or prevent radon entry. It can make its way through the floorboards into occupied areas like bedrooms, living rooms and offices. The best way to prevent radon entry in crawlspaces is to seal them and install a radon mitigation system.

In crawlspaces that have dirt or gravel floors, we seal your crawlspace with an airtight membrane called a vapor barrier. All stored items and debris must be removed from the ground prior to the installation of the vapor barrier. If there are sharp objects or sharp gravel we can install a layer of tar paper over the floor before placing the barrier. This helps prevent the plastic from being ripped or torn when placing storage items back in the area.

We then install the vapor barrier which is a minimum 6-12 mil cross-laminate. We secure the plastic membrane to the foundation walls or footings using wooden furring and concrete nails. Once the plastic is secured to the foundation walls, the entire perimeter is sealed including any seams, splices and penetrations to create an air-tight barrier to block the radon gas. The radon mitigation system is then tied directly to the soil under the membrane. The system creates a twenty-four-hour vacuum that continually pulls the radon out to vent above the roof of the house.

In crawlspaces that have concrete floors radon levels can be reduced by creating a vacuum in the soil under the concrete slab. Many concrete crawlspaces have a large number of cracks. These cracks, along with the corner where the floor meets the foundation wall are sealed to create a more airtight barrier. The radon system is installed by drilling a hole through the concrete to access the soil underneath. The mitigation system creates a constant vacuum in this soil to vent the radon out above the roof of the house.