A very serious issue that concrete contractors need to be aware of concerns the use of 6-mil polyethylene as a vapor barrier under a concrete slab. Despite what some building codes indicate, specification and installation of recycled polyethylene as a vapor retarder is now considered to be a defective specification by many attorneys practicing construction law. Poly presents three problems: it does not have the puncture resistance necessary to withstand construction traffic, it can get brittle and decompose over time, and it is not impermeable enough to protect modern floor coverings. Even recycled 10-, 15- or 20-mil poly does not comply with the requirements of ASTM E 1745, “Standard Specification for Plastic Water Vapor Retarders Used in Contact with Soils or Granular Fill under Concrete Slabs.” Owners, architects, and contractors should specify and install products in compliance with this standard or risk claims of defective specifications or products. Flooring failures and a national mold epidemic have created an environment of unparalleled liability. We feel that the minimum vapor barrier should have a permeance of 0.01 perm or below (See page 63, Concrete Floors and Moisture by Howard Kanare/Portland Cement Association), should meet ASTM E 1745 Class A requirements, should be installed according to ASTM E 1643, “Standard Practice for Water Vapor Retarders Used in Contact with Earth of Granular Fill Under Concrete Slabs,” and should be located directly beneath the slab as described in ACI 302.1R-04, “Guide for Concrete Floor and Slab Construction.” Since insurance policies now have mold exclusions, if an architect specifies or a contractor installs 6-mil poly or value engineers a specified vapor barrier to poly, and mold occurs on or under the floor covering, the design firm and/or contractor could lose their business.
— Paul Blasdel, Caroll Bryan, Esq. Stego Industries, San Juan Capistrano, Calif.