If you have the need to retain soil or prevent erosion, a wall may be just the thing. Any projects under 18″ in total height are simple and straightforward. Once you go over that height the project becomes more complicated, but with the proper machinery and prep, it’s still entirely doable.
Prepare the Site Dig back the soil and level the ground for the entire length of the wall and also about 3 – 4 feet back for anything over that magic 18″ number. This may require some of that machinery or just a bunch of generous friends.
The Base Lay a gravel base about 6″ deep along the line of the proposed wall and pack it down well. This helps with drainage, so don’t skip it and don’t skimp on the depth. Make absolutely sure that your first course or layer of wall is level. Whether you’re working with stone or wood, use a level to double and triple check.
Use Deadmen When you lay the second course there are a few things to consider. First off, if your wall will be any higher than 18″, you will need deadmen or tiebacks. These act like framing for the wall; running perpendicular to the face of the wall and back into the ground (like a “T”). At the other end of the tiebacks, you will lay a framed structure that nearly mirrors the outside wall.
For instance, the tiebacks start on the second level and are placed about 6 to 8 feet apart on center. They generally reach back about 3 to 4 feet and have a support underneath so that they are level. Then, a layer of wood (4×4 or 6×6, whatever works for the height of your wall material) is placed on top so that the next set of tiebacks (on the fourth course of the wall) sits on top of it. Make sense?
Consider Rebar If your wall is stone and higher than 18″, it’s a good idea to use rebar cored through each course to connect them. For wood retaining walls, spikes can be used (8″ or 10″) to connect each layer and the tiebacks together.
Set it Back Be sure to set each layer back from the front of the layer underneath by about ½”. Often stone wall systems are made that way, with a lip on the back end to hold it all steady. This is to prevent toppling.
Drainage Once your wall is built, lay a slotted drainage pipe along the bottom behind the first course and backfill with gravel. This will help to direct water away from the wall. Cover with soil, seed the top and voila, you’ve installed a retaining wall that will stand the test of time.