TerraDrain® Sheet 101 & 121 prefabricated drains are constructed using a formed polystyrene drainage core with a nonwoven filter fabric bonded to one side. The filter fabric is bonded to each dimple to prevent soil intrusion into the flow channels while allowing water to freely enter the drain core from one side.
TerraDrain® Sheet 121 provides additional protection for soft waterproofing membranes. The high-strength polymeric film is bonded to the flat side of the drainage core to prevent membrane intrusion into the back of the dimple.