Heres whats important in the new ACI Guide to Floor and Slab Construction.
Submitted by Dennis Keane, Stego Industries, LLC
Written by William D. Palmer Jr.
Originally published on Concrete Construction in August, 2015.
Protecting a concrete floor on ground from the moisture coming up from below has become an important issue, especially when moisture-sensitive floor coverings are used. The old chart (Fig. 3.1 in 302.1R-04) that showed when to use a vapor retarder/barrier has been replaced by one that is much more specific (Section 5.2.3) and with a lot more detail. Basically, if the intended use of the building above the slab involves anything that could be sensitive to moisture (flooring, adhesives, underlayments, coatings, goods stored on the slab), or if the building will have a climate-controlled environment, a vapor barrier is required. And in almost all cases the slab should be placed directly in contact with the vapor barrier. The old way of placing the vapor barrier and covering it with a blotter layer of granular material, that inevitably ends up trapping water next to the slab, has largely been abandoned by Committee 302. ÏThe term conditioned space was causing some confusion, says committee member Scott Tarr, North S.Tarr Concrete Consulting. ÏI think the changes have cleared that up.