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.
The thickness of vapor barrier sheeting, measured in mils, is one of the most significant specification decisions a homeowner or contractor makes. The material specification should match the specific moisture conditions and use patterns of the space, and we assess both before recommending a product.
Seam treatment is equally important to the material specification when it comes to achieving a functioning vapor barrier system. A perfectly spec'd 20-mil liner installed with poorly treated seams performs no better than a budget barrier at preventing moisture migration.
A properly installed vapor barrier extends up the wall from the floor, typically to the sill plate, and is secured with concrete adhesive or mechanical fasteners at the top. 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. 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.
Full perimeter coverage is non-negotiable in our installation standard.
You receive documentation of your warranty before we leave the property.
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.
We install vapor barrier systems under flooring or as a standalone moisture management layer in unfinished basements.
Drainage board integration is recommended for Adams basements that experience both seasonal dampness and occasional liquid intrusion.
Adding a properly sized dehumidifier completes the moisture management system and ensures consistent relative humidity control regardless of outdoor conditions.
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. They went with 20-mil for our space and the installation looks perfect. 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. The proper wall-to-sill installation finally completed our moisture protection. Great work from a team that clearly knows what they are doing."
Our certified team is ready to assess your crawl space and provide a clear, honest recommendation
