How to Drain a Composite Retaining Wall

Retaining walls can be made of several types of materials, including composite blocks. These are hollow blocks that are stacked in a wall and filled with crushed stone. As with any retaining wall, a drainage system must be installed along the base of a composite retaining wall to drain water away that would otherwise destabilize the wall by washing away the soil underneath it.

Shovel
Tape measure
Crushed gravel
Tamp
Composite wall blocks
Drain tile
Landscaping fabric
Drainage aggregate

Instructions

- 1
  Dig a trench where you are installing the wall. The trench should be about 12 inches deep and 8 inches wide.
- 2
  Fill the trench with 3 inches of crushed gravel, and tamp it down. Add a second 3-inch layer, and tamp that down.
- 3
  Place the first course of composite blocks into the trench, and fill the blocks with crushed gravel.
- 4
  Wrap the drain tile in landscaping fabric. Drain tile is a perforated plastic pipe that carries water away from the retaining wall.
- 5
  Lay the wrapped drain tile into the trench, centering it in between the back edge of the composite blocks and the back wall of the trench.
- 6
  Cover the drain tile with drainage aggregate, using enough aggregate to reach the top of the composite blocks.

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