Drainage Behind Retaining Wall: How to Stop Retaining Walls from Failing

Why do retaining walls fail?

There are many reasons why a retaining wall will fail. However, the unifying thread through all of those failures is water. Walls fail because the builder did not use enough class 5  fill. Without the right amount of base material, water builds up underneath the wall and pushes the base layer out. Retaining walls also fail because the base layer was not leveled properly. An unlevel base layer allows areas for water to wash away certain sections more than others, which creates an unstable wall. In other failed walls, we’ve seen water collect behind the wall. This collected water freezes and expands which pushes on the wall, causing it to fall over. The common thread through all of these problems is improper preparation for water.

Retaining Wall Behind Drainage Diagram

Having an experienced landscape company build your retaining wall will take all the headaches and worries out of your wall.

4 Tips to Building the Best Retaining Wall

Use crushed stone behind the wall

  • Loose gravel and stones don’t hold water like soil does. Soil holds water, so the dirt will expand and contract during winter, thus pushing on the wall and eventually toppling it over.
  • We go about 6″-8″ deep behind the wall with loose rock (usually crushed granite) and up to the second row from the top. This loose rock is probably more than other companies would use, but we would rather allow more water to flow behind the wall and out than not have enough.

Use fabric behind the wall

  • Fabric keeps rock and soil separate.
  • Install it in a U shape way behind the wall.
  • Fabric keeps soil from leeching out of walls.

Use drainage tubing behind the wall

  • Slope the tubing from one end of the wall to the other or from the ends to the middle.
  • Cut holes into the wall to let water out. These are called weeping holes.

Use the correct stones

  • Stones should be 60-80 pounds. Small Menards ones don’t hold soil back because there are too many moving parts and not enough weight.
  • Contractor-grade blocks are built to last and hold soil and water much better than cheaper versions.
  • Pin systems can work to make a straight vertical wall. Otherwise set backs have to be used.


Ensure your retaining wall stands strong for years to come by using the correct type of stones for your project and by choosing a design that works well for your soil and lawn type. Our experts are happy to provide solutions for your retaining wall needs; just give us a call at 763-568-7251 or submit a message through our quick quote system.