Solving a Drainage Problem in a 3-Foot Gap Between a Patio and Retaining Wall

Water was pooling up in a ditch near a retaining wall. Without proper drainage, this would erode the ground underneath, and the wall would collapse. Ideally, the drain would go on the other side of the wall, but due to some unique challenges, this spot proved the best for a large drain to remove water pooling and send it away from the nearby home.

Completed in this French Drain project:

1. Dug trench that was sloped away from home
2. Installed french drain to collect water that pools in trench and carry away from home
3. Wrap drain in non-woven geotextile fabric (allows water seamlessly in while keeping everything else out)
4. Fill wrap with drainage rocks and close wrap
5. Fill remainder of trench with drainage rocks
6. Cover trench

This isn't totally necessarily if you measure the slope with levels, but I like to use a hose to test the trench. All looked good here, and water at the top of the trench quickly made it to the bottom. This simulated what would happen with rain water collecting in the trench.

Holes facing down is what you want. The lowest part of the drain is lower than the holes. This makes it so water flows into the holes and collects at the bottom of the drain, which is then carried downhill by the slope - continuously flowing collected rain water away from your home and patio.

Water flows through this nonwovn geotextile fabric wrap seamlessly. It never ceases to amaze me. It's like the wrap is not even there for water flow.

Normally, we'd cover the trench with dirt to give a clean look, but for this project the entire surrounding area was going to be river rocks, so it was better to just leave it as rocks for increased drainage.