FT Synthetics HYDRA is a breathable synthetic roofing underlayment designed to add an extra layer of water resistant protection under your primary roofing material, and at the same time help the release of trapped moisture due to poor attic ventilation. HYDRA is designed with an internal monolithic membrane. This structure provides outstanding vapor permeability using an advanced chemical transfer of water vapor and acts as a liquid water barrier under all weather conditions. HYDRA includes our slip-resistant GRIPSPOT™ technology top surface for superior walkability and HYDRY™ technology for faster roof deck drying. HYDRA is approved for installation over plywood or OSB roof decking with proper fasteners on roof slopes 2:12 and greater. It is an ideal solution for breathable roof systems such as metal, tile, slate, and cedar shingles, but can also be used under asphalt or synthetic shingles.