HAL-TEX Cor-Ply is a two-ply building paper with 3 mm deep corrugations. The corrugations prevent moisture entrapment by creating a drainage gap between the outer cladding and the structural wall. This gap will permit drainage of errant moisture and allow airflow behind the cladding for better drying. These rainscreen/drainage benefits are provided very economically in terms of material cost and labor savings on installation. The product is designed not just to be your average two-ply 30 minute paper. It is a 2 ply 30 minute WRB that provides the added bonus of assured drainage.