How To Build A French Drain Behind A Retaining Wall. Otherwise, water moving down the hill will build up. How a french drain works.
A french drain or a drain tile is built by filling a trench with gravel and a perforated pipe is used at the bottom to divert underground water.
Is a drain always needed or can one get away with like a foot of.5 to 1 rock behind the wall? Poor drainage resulting in saturated soil and frost heaving is the main cause of failure. Our retaining wall will be two sleepers high, but you can make it lower or higher depending on your requirements. Install french drains at the foundation/perimeter of your house.