A composite drainboard includes a patterned substrate core having an inward surface, and opposed outward facing surface. The substrate core comprises a plurality of projections, forming concavities on the inward surface. A first geotextile membrane is attached to the substrate core and covers the outward facing surface. A second membrane is attached to the substrate core to cover the inward facing surface and the concavities to provide a substantially smooth coating to the inward surface. The second membrane at least partially absorbs a liquid applied waterproofing.