Laminated sheet for protecting underground vertical walls

A coextruded laminated sheet useful to facilitate the drainage of ground water to protect underground vertical walls and foundations when placed thereagainst, said laminated sheet having an array of spaced apart projections extending laterally outwardly from one side thereof and forming a series of drainage channels, and comprising a core of crystalline polystyrene providing compression strength and creep resistance properties to said laminated sheet, a first non-pervious layer of high density polyethylene overlying and laminated to one side of said core and a second non-pervious layer of high density polyethylene overlying and laminated to the other side of said core, said first and second layers providing chemical and impact resistance to said laminated sheet.

A coextruded laminated sheet according to claim 17 wherein said projections extend outwardly, and have a dimension lateral to and a dimension parallel to said laminated sheet of about the same.

An underground drainage system for a basement or the like comprising a vertical foundation wall in combination with a laminated sheet laid along an exposed face of said foundation wall, said laminated sheet having a planar base portion and an array of spaced apart projections extending laterally outwardly from one side of said base portion and forming a series of drainage channels, and comprising a layer of crystalline polystyrene providing compression strength and creep resistance properties to said laminated sheet, and at least one non-pervious layer of polyolefin overlying and laminated to one side of said crystalline polystyrene layer, and providing chemical and impact resistance to said laminated sheet.