The purpose of a vapor barrier is straightforward: prevent ground vapor from rising into your crawl space or basement floor, where it can saturate wood framing, insulation, and HVAC equipment over time. Understanding what a proper vapor barrier consists of, however, goes well beyond simply laying plastic on the floor.
Standard 6-mil poly sheeting has a relatively high vapor permeance rating, meaning it allows some moisture vapor to pass through over time, particularly as it ages and develops micro-perforations from foot traffic and environmental factors. For most homes in Windsor, WI, 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. We use butyl tape exclusively for seam sealing, both because of its long-term adhesion to polyethylene and its resistance to moisture and temperature cycling.
Wall coverage is the third major element of a complete vapor barrier installation that is frequently done incorrectly in Windsor, WI homes. 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.
HVAC equipment and ductwork located in a humid crawl space corrodes faster, loses efficiency, and requires earlier replacement than equipment in a properly sealed environment. If the barrier is incomplete or poorly sealed, a dehumidifier simply works harder against an unlimited moisture supply, running continuously and consuming excessive energy without achieving target humidity levels.
Our installers are trained on manufacturer specifications for every product we use.
We source reinforced 20-mil poly sheeting and commercial butyl tape, not the hardware store equivalent.
We extend the barrier up every wall to the sill plate, closing the moisture entry pathway that floor-only installations miss.
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.
Upgrading from 6-mil to 20-mil sheeting with proper seam sealing delivers measurably improved moisture performance in most cases.
The installation includes full seaming, perimeter taping, and wall coverage to the base of the finished wall or sill plate.
Drainage board integration is recommended for Windsor basements that experience both seasonal dampness and occasional liquid intrusion.
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.
Inspection findings are documented with photos and a written report detailing any deficiencies and recommended corrective actions.
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 completely replaced the barrier with a 20-mil system properly taped and sealed wall-to-wall. 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 20-mil they installed is rock solid and the seams are all properly taped. 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
