A retaining wall must provide a way to release the water that builds up in the slope behind it. Without a pressure-relief system, the weight of the water in the soil would crack or even buckle the wall. Weep holes, which are lengths of ¾-inch pipe inserted along the top of the first course, escort some of the water out. The other part of the system is a plastic drainpipe covered with gravel. As water accumulates behind the wall, it percolates through the gravel into the drainpipe, which carries it off safely. Retaining walls must be stronger than freestanding walls. Insert rebar in the footing when you pour it; this should be done at every three blocks or at intervals specified by your local codes. As the last step, fill the cores around the rebar with mortar from the bottom to top. Expect to spend 20-36 hours building a 3x10-foot concrete-block retaining wall. Before you begin, you’ll need to design the layout and pour the footing.
