a product , and a wall system utilizing such product , adapted to allow drainage of moisture from a wall of a structure . a sheet of corrugated material forms a plurality of ridges and grooves on opposite sides of the sheet of corrugated material . the sheet of corrugated material is relatively inflexible under a force applied generally perpendicular to the sheet . the sheet of corrugated material has a multiplicity of perforations . a sheet of water permeable material is affixed to one side of the sheet of corrugated material . the product is flexible in a direction along the plurality of ridges and grooves allowing the product to be stocked in roll form . a method of providing drainage of moisture from a wall structure is also disclosed .