Abstract: A construction element for foundation drainage has an integral, flexible, and substantially water-impervious panel lying generally in a plane and formed with respective arrays of inner and outer bumps to opposite sides of the plane. The outer bumps form outwardly open outer flow channels on the outer face. Normally the panel is applied to a vertical foundation wall with the inner bumps bearing against the wall and the outer passages vertical and opening outward away from the wall. The inner bumps and outer bumps are offset to one another in the plane in two perpendicular directions. Thus the channels communicate also in these two directions and the element can be rolled up. A water-pervious and rigid filter sheet overlies the outer bumps, is spaced outward from the plane, and outwardly closes the channels so that water can filter through the sheet and flow down the channels.