What is the mil rating of a vapor barrier that must be installed under concrete slab?

What is the mil rating of a vapor barrier that must be installed under concrete slab?

• A. 2
• B. 1
• C. 6
• D. 4

Answer: (C)

A vapor barrier under a concrete slab is used to limit moisture moving from the soil into the slab and the finished flooring above. The thickness is measured in mils, and six mil polyethylene is the standard minimum for a vapor retarder in typical construction. A thinner barrier, like one or two mil, would be easily damaged and offer far less protection; four mil is also thinner than the common minimum. While some projects or climates may require thicker barriers, six mil is the expected standard in most cases.

A vapor barrier under a concrete slab is used to limit moisture moving from the soil into the slab and the finished flooring above. The thickness is measured in mils, and six mil polyethylene is the standard minimum for a vapor retarder in typical construction. A thinner barrier, like one or two mil, would be easily damaged and offer far less protection; four mil is also thinner than the common minimum. While some projects or climates may require thicker barriers, six mil is the expected standard in most cases.