DIY Low Cost Retaining Walls

Divide the height that you plan to make your wall, measured in inches, by 10. Add 6 to the result. This result is your foundation trench depth, in inches. As an example, if you plan on a 3-foot, or 36-inch, wall, then your foundation trench needs to be 3.6 + 6 = 9.6 inches deep.

Mark the line followed by the outer face of the retaining wall in front of the hill. Use spray paint or string tied between posts. Dig a trench for the foundation behind the line you marked, 24 inches wide.

Pour 3 inches of 3/4-inch gravel evenly over the bottom of the trench. Compact it with a jumping jack or similar powered compactor. Pour another 3-inch layer of gravel. Compact it.

Lay the bottom course of stones in the trench. Use the widest stones for the bottom row, so that upper rows don't overhang and overbalance. Use a level to check that the stones are lying flat.

Lay the next row on top of the first. Use the widest of the remaining stones for each row, to avoid overbalancing the wall. Stagger the joints between stones with each row. No joint should be directly above a joint in the rows immediately below and above it. Use small stones to fill in gaps and to bring an edge up to level. Use the level regularly as you go, to make sure you are keeping the rows horizontal.

Fill the gap between the wall and the hill face with soil and gravel. Use a shovel to save money by not renting a backhoe.