Why drainage matters so much
Wet soil is much heavier than dry soil, and clay, which is common around Pittsburgh, holds water. A wall with no way to drain is holding back both. In winter, water trapped behind the wall can freeze and expand. Good drainage gives that water a path out: clean gravel lets it move down, a perforated pipe at the base carries it away, and weep holes or outlets let it out through or around the wall.
Signs of a drainage problem
- Water seeping through the face of the wall or staining it
- Soggy ground or puddles at the base after rain
- Soil or fine gravel washing out of the joints
- A downspout or driveway sending water toward the top of the wall
- The wall starting to lean or bulge
If the wall is already leaning, drainage alone may not be enough. See retaining wall repair and when you need a retaining wall.