Otherwise water moving down the hill will build up behind the wall and undermine it.
Installing french drain behind retaining wall.
Mar 19 2014 when building a retaining wall lay perforated drainage tubing at the base of the wall slightly above ground level so runoff can drain out without undermining your wall.
This is so that when water gets into the space it does not become bogged down in soil but instead can flow down the wall to the drains or weep holes.
Check out this video for some simple instructions on installing a french drain behind an 18 to 24 tall retaining wall before it is backfilled with dirt.
For proper drainage the first 12 inches of space behind a retaining wall should be filled with crushed stone or gravel.
The pipe should rest on the same compacted gravel base or concrete footing that supports the wall.
Water that s allowed to build up behind retaining walls can damage a wall or cause it to give way.
Typically drain lines are installed at the base of new walls before the soil is backfilled.
Fill the trench with topsoil and compact to completely cover the entire french drain system.
If you re building a retaining wall add a french drain behind the first course of stones or blocks.