The most common thing present in all vented crawl spaces in North Carolina is moisture. This is caused by both hot and humid summers along with ample rains in the Spring and Fall. Vented crawl spaces work best in areas that are less humid than the Triangle and building codes are shifting towards sealed crawl spaces and higher standards for vapor barrier installation. The majority of homes in the Triangle area were built with a dirt crawl space beneath the home and are vented. Depending on the age of your home your vapor barrier may be as simple as a sheet of plastic laid on the ground or it may not have a vapor barrier at all.

Moisture from the ground and condensation from crawl space vents combine to create all sorts of problems under your home. This moisture creates mold, mildew, dry rot and allows insects and other pests to thrive. A vapor barrier is key to stopping this moisture. If there is excess moisture under your home you may see signs of efflorescence on the foundation walls or even standing water in your crawl space. Efflorescence is the white or chalky looking marks that are seen when moisture is penetrating the cinder block foundation. It may be caused by an exterior drainage issue, excess standing water or other moisture source. Excessive water may require additional measures like a dehumidifier or sump pump or correction of the drainage problem but the vapor barrier needs to be addressed as the first step in a solution.

Properly installed a vapor barrier prevents water from the ground from migrating to the floor joists, insulation, sub-flooring, and other materials located in a crawl space. As the ground becomes saturated during rainfall, moisture moves through the ground like a sponge, coming into contact with the soil underneath your home. Even with a properly sealed foundation wall and good drainage, moisture will migrate through the soil under the foundation creating conditions perfect for mold growth, musty odors, insects and other problems.

Install a new vapor barrier

A correctly installed crawl space vapor barrier should be overlapped and taped to eliminate gaps in the coverage. It should also extend up to foundation walls and footings underneath the home to ensure that moisture can not permeate the barrier and moisture does not seep around it. Current building code specifies a minimum thickness of 6mm but a thicker 12mm plastic liner performs better and is less likely to be damaged by any maintenance or access to the crawl space.

Sealed Vapor Barrier

If you are having excessive moisture problems like standing water, efflorescence, mold growth or puddles underneath your home. Triangle Crawl Space Solutions will recommend a sealed vapor barrier to help address these problems. A sealed vapor barrier provides additional protection against water and moisture infiltrating your crawl space. A sealed vapor barrier uses the same heavy duty 12 mil plastic liner as the standard vapor barrier but the plastic liner is fixed to the foundation walls and the individual footings of the home are wrapped. It extends up the piers and foundation wall to block moisture from the crawl space. A three inch gap is left between the top of the vapor barrier and the sill board of the home to allow for any future inspections (commonly for pest inspections).

Once your new vapor barrier is properly installed TCSS can discuss any further needs to remove moisture like a sump pump or dehumidifier based on your specific moisture levels and the condition of your crawl space. It all starts with a free assessment of your crawl spaceā€¦just give us a call.


FAQ and Common Questions: Vapor Barriers