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Drainage Boards

Another approach to waterproofing with applied sheet materials is to use drainage boards, with or without waterproofing on the concrete wall. These dimpled plastic sheets are available from several manufacturers and come in various length rolls, ranging from 4 feet to 9 feet 9 inches tall.

The dimpled side is placed toward the foundation and holds the sheet about ½ inch from the wall. A termination strip is attached to the wall at the top. The plastic serves as a waterproofing membrane, keeping water from penetrating to the surface of the wall, and as protection for the membrane on the wall during backfilling. Any water that may get through (by condensation or leakage) can trickle down to the foundation drains through the space formed by the dimples.

Different versions of this type of product have filter fabric attached to the dimpled side which is then installed away from the wall and forms the route for water to flow down to the drain. This gap can also serve to dry moisture that remains in the concrete wall from construction.

Some drainage boards incorporate solid materials that are porous enough to allow water to flow down while supplying some insulating value to the wall. Still others uses twisted or deformed wire covered with a filter fabric to provide the drainage space. There are lots of options for this component of the overall system.

Some additional points to consider:

  • The dimpled drainage board can help reduce intermittent hydrostatic pressure because it moves water away before pressure can build against the foundation.

  • A dampproofing coating is advisable behind drainage boards to prevent incidental moisture infiltration as long as it doesn't interfere with performance or the manufacturer's specifications.

  • Some drainage panels, as part of overall systems, use specially designed drainage boards in combination with waterproofing membranes, to replace drain tile pipes (such as the Tremco system).

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