How to Install Drainage in a Cinder Block Retaining Wall

A cinder-block retaining wall's job is to hold back an incredible amount of pressure from the soil behind it. When this soil becomes wet, it applies even more pressure. The cinder-block retaining wall may start to lean, buckle and crack from all this pressure. While you cannot stop the soil behind the retaining wall from becoming wet, you can set up a drainage system to guide as much of the water as possible out from behind the retaining wall.

Hand tamper
Drainage aggregate
Metal rake
Landscape fabric
Scissors
Perforated drain pipe
Soil

Instructions

- 1
  Build the first three layers of cinder blocks for the retaining wall. Flatten out the ground about 12 inches behind the cinder blocks, with a hand tamper. Pour 2-inch layer of drainage aggregate on the flattened surface.
- 2
  Smooth out the aggregate with a metal rake. Determine which end of the retaining wall you want water to drain to. Slope the aggregate slightly toward that end.
- 3
  Cut one or two strips of landscape fabric to equal the length of the cinder block-retaining wall. Lay the strips over the drainage aggregate and slightly up the hill. If you needed to use two strips, overlap them by about 3 inches.
- 4
  Lay a perforated drain pipe behind the cinder blocks, on the landscape fabric. Extend the drain pipe's draining end 1 to 2 inches past the retaining wall's end. Fold the landscape fabric extending up the hill over the top of the perforated drain pipe.
- 5
  Pour more drainage aggregate on top of the landscape fabric, in a 12-inch-wide layer, up to the top surface of the third cinder-block level. Backfill behind the aggregate with soil. Tamp the aggregate and soil down with a hand tamper.
- 6
  Continue to build up your cinder-block retaining wall, adding drainage aggregate directly behind the cinder blocks and soil behind the aggregate.

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