Drainage and insulating material for subterranean walls

A drainage material for subterranean walls comprising a plurality of generally planar panels adapted to be applied in edge-to-edge relation substantially covering the exterior surface of said wall, while said wall is still free-standing and prior to the application of backfill material to said outer wall surface, each of said panels including:

• a. a planar slab formed of a material which is normally substantially moisture impervious, but subject to the passage of moisture therethrough as a result of possibly imperfect manufacture thereof, or as a result of cracking, breaking, crushing or piercing thereof by heavy rocks included in the backfill material when said material is applied, said slab having fluid flow passages formed therein parallel to its plane through which ground moisture may flow downwardly to the lower edge of said panel by gravity, said passages opening exteriorly of said slab at areas distributed evenly over the entire area of at least one face thereof to permit said ground moisture to enter thereinto, and
• b. a sheet of filter material covering any surface of said slab through which said flow passages open, whereby to permit the passage of moisture to said flow passages therethrough, but to inhibit the passage of sand, ground silt or the like.