A vapor barrier is a polyethylene sheeting system installed on the ground and walls of a crawl space or basement to block ground moisture from migrating into the structural environment above. Understanding what a proper vapor barrier consists of, however, goes well beyond simply laying plastic on the floor.
A mil is one-thousandth of an inch, and the difference between a 6-mil sheet and a 20-mil sheet is significant in terms of puncture resistance, lifespan, and moisture vapor transmission rate. For most homes in Grand Ledge, MI, we recommend a minimum 10-mil product for general installation and a 20-mil product for spaces with high moisture loads or frequent access requirements.
Seam treatment is equally important to the material specification when it comes to achieving a functioning vapor barrier system. Seam quality is one of the most overlooked and most impactful aspects of the vapor barrier installation.
Covering only the floor and stopping the barrier at the wall-floor junction leaves the porous block or concrete foundation walls as an open pathway for moisture to enter the crawl space environment. The combination of floor coverage, properly lapped and taped seams, and full wall coverage to the sill plate creates a complete moisture envelope that dramatically reduces crawl space humidity and protects the wood framing above.
It also creates ideal conditions for mold and mildew growth on wood surfaces and insulation, contributing to indoor air quality problems in the living space above. A well-installed vapor barrier is also a prerequisite for effective dehumidifier integration in crawl spaces where mechanical moisture extraction is warranted.
Every installation meets or exceeds Grand Ledge, MI building standards.
We source reinforced 20-mil poly sheeting and commercial butyl tape, not the hardware store equivalent.
Full perimeter coverage is non-negotiable in our installation standard.
Our vapor barrier installations carry a written warranty covering materials and workmanship.
We install reinforced polyethylene sheeting across the entire crawl space floor with full wall coverage and butyl-taped seams throughout.
We remove deteriorated existing barriers, prepare the substrate, and install a properly spec'd replacement that meets current installation standards.
We install vapor barrier systems under flooring or as a standalone moisture management layer in unfinished basements.
This combination approach addresses both vapor diffusion and water management in a single installation.
Full crawl space encapsulation combines a complete vapor barrier system with a dedicated dehumidifier sized for the space to achieve and maintain target humidity levels year-round.
We offer post-installation inspections for vapor barriers installed by other contractors, as well as for our own older installations, to assess barrier condition, seam integrity, and wall coverage completeness.
We measure the space, assess existing moisture conditions, document any existing barrier or mold, and identify all penetrations that will need to be addressed in the installation
Based on site conditions, we specify the appropriate mil rating, calculate material quantities, and plan the seaming layout for maximum coverage and minimum waste
Sheeting is laid, overlapped at 12 inches minimum, taped with butyl tape at all seams, and extended up all walls with mechanical fastening at the top edge
We walk through the completed installation with you, confirm all seams and coverages are complete, and provide written warranty documentation before leaving
"We had a previous vapor barrier installation that was barely 6-mil and had separated seams throughout. The humidity in our crawl space was unacceptable and we were starting to see mold on the floor joists. JCB Waterproofing and Construction removed the old liner and installed a commercial-grade system with butyl tape seams throughout. The difference in our indoor air quality was noticeable within a week."
"Very professional team that explained the difference between the grades of vapor barrier sheeting before recommending anything. The material quality and seaming were both done to a very high standard. We can already see the humidity meter reading dropping consistently."
"The crew extended the barrier all the way up the walls to the sill plate, which the contractor who did our original installation did not do. We had been missing that wall coverage and did not even know it. Great work from a team that clearly knows what they are doing."
Do not let ground moisture continue to damage your floor framing and indoor air quality
