Grace Tri-Flex 30 synthetic roofing underlayment is a premium water-shedding underlayment. Grace Tri-Flex 30 is not designed to protect against standing water or water moving “upslope” resulting from factors such as accumulated snow, ice, wind-driven rain, or debris. For protection from standing water or water moving “upslope”, it is recommended that Grace Ice & Water Shield self-adhered underlayment be used. These two types of underlaymetns can be used independent of each other or together to provide a premium system, depending on the design needs.