USG Durock™ Brand Performance Flooring products are primarily meant to be used over properly prepared concrete. The products can also be used with metal lath over engineer-approved, APA-Rated exterior glue plywood or oriented strand board (OSB) (i.e., APA-Rated Exterior or Exposure 1 panels) wood subfloors following the Tile Council of North America's F-185-11 specification at a minimum ½ in. depth.