Sealing and venting (Radon – active vs. passive systems)

Sealing – Ground water is moisture which pushes vertically into many crawlspaces. For this reason, it’s extremely important to fully seal the crawlspace across the dirt floor and then up the walls of the crawlspace. The top of the vapor barrier is then attached to the concrete foundation with concrete nails, and sealed. All seams within the vapor barrier should overlap by 6 inches and be completely sealed so moisture cannot migrate between the layers and into the crawlspace. 

The membrane and sealing need to surround any posts or caissons as well and be sealed at the top against the caisson or post.

Crawlspaces and basements can have many moisture issues, but we’ll focus on crawlspaces for now. 

Exterior sealing

The exterior damp proofing or waterproofing previously mentioned is crucial. The 2021 code requires crawl spaces to be vented, and this can be done in numerous fashions. Damp proofing is pictured below with the engineered drainage system at the bottom of the wall.

We’ve all seen HVAC vents in floors, and I recommend that one of these be installed, but  without attaching the air supply line.  Instead, the vent will open directly into the crawlspace, which, I know, seems antithetical to air quality, but we’re not done yet. 

Now, we will install a continuously running fan in the crawl space ( as far away as possible and on a diagonal from the floor vent)  to pull air out of the living space, across the crawl space to the fan. The fan would be attached to a pipe that leads out of the crawlspace, and provide 24/7 venting.