Creating a Moisture & Vapor Barrier Under Concrete Slab
It’s no secret that moisture can cause problems in your foundations and walls. That’s why it’s essential to prevent moisture buildup with a vapor barrier under concrete slabss. When you properly install a vapor barrier underneath a concrete slab, you can prevent moisture related issues such as mold and mildew, delamination in the overlay or sealer, joint failure, spalling, cracking, and deterioration.
Vapor barriers should be installed in both commercial and residential foundations to help prevent expensive repairs due to moisture damage.
Vapor Barriers Save Time & Money
One of the most important reasons to utilize a high-quality vapor barrier is simply to protect an expensive construction investment, particularly the floor covering. Water below the concrete slab can diffuse through the slab as vapor, then condense under the flooring, which can emulsify some adhesive and destroy the floor covering. Water vapor diffusing through the concrete slab can also lead to deformation and discoloration of the floor covering material, leading to costly repairs or even replacement.
The cost of a vapor barrier (installed before the concrete placement) is significantly less than an expensive water problem repair, especially when it affects the flooring of an entire building. By reducing the moisture gradient and diffusion in your slab, you can virtually eliminate any issues caused by under-slab water vapor migration.
Why Install a Concrete Vapor Barrier
A vapor barrier under your slab will also protect you from harmful ground pollutants like radon gas. Post-frame buildings with metal roofs, and especially buildings with minimal insulation, hold warm, moist air. That air condenses on the cooler concrete floor. In larger commercial buildings and warehouses, that moisture can cause the flooring sealer and joints to fail, and where water pools, the concrete often spalls and cracks. Moreover, where there is moisture, there is a potential for mold growth. Installing the proper vapor barrier beneath the slab will save you money, health, and aggravation.
There is a variety of polyethylene sheeting referred to as a “vapor barrier” or a “vapor retarder,” but not all of them can be applied as an under-slab vapor barrier. Vapor retarders are manufactured to meet ASTM E1745 specifications (standard specification for water vapor retarders used in contact with soil or granular fill under concrete slabs). There are three classifications: A, B, and C, with A being the most resistant to tearing and punctures and C being the least resistant.
Choosing the Right Vapor Barrier
Americover offers a variety of concrete slab vapor barriers and tapes, all of which meet ASTM E1745 specifications. This standard ensures the poly sheeting’s resistance to vapor migration and meets industry standards for tensile strength and puncture resistance. The most commonly used vapor barrier under concrete slabs is polyethylene (poly) plastic sheeting with a thickness of 10 mil or 15 mil.
All Americover Vapor Barriers are composed of virgin polyolefin resins and offered in 10 mil, 15 mil, and 20 mil. These are high-performance materials designed to stop moisture migration and prevent gases or contaminants from infiltrating the concrete slab, flooring, and walls. These vapor barriers can be installed over tamped earth, sand or aggregate base: simply unroll and completely cover the area receiving the slab, overlap the seams by 6 inches and seal by heat welding or with sealing tape. All exposed penetrations should also be sealed.
What Vapor Barriers Should You Buy?
Polyethylene sheeting is available at most building supply stores. However, not all poly sheeting qualifies as a vapor barrier. Watch out for recycled or “regrind” polyethylene, which may contain impurities and become brittle. Sheeting that tears diminishes the effectiveness of a vapor barrier.
Americover virgin polyethylene sheeting is your best bet. Americover offers durable string-reinforced vapor barriers made from 100% virgin polyethylene, which comes in 6 mil to 20 mil.
Browse our selection of vapor barriers, radiant barriers, and vapor tape: