Retaining walls serve both a functional as well as aesthetic purpose in landscaping. Built of many different materials ranging from railroad ties, concrete, cement blocks, bricks, and natural stone, to manmade blocks that replicate natural materials, they serve to hold back slopes from eroding. They also provide a functional wall for climbing vines and close-growing perennials. You can also plant herbs like thyme in between the building materials for a beautiful fragrant cover. Terraces formed from retaining walls provide a flat, level area for plantings as well as inhibiting run-off. If you have a slope that prevents you from installing things like pools, patios, playgrounds, parking areas, or decks, you can build a level area to accommodate them by installing a retaining wall. Retaining walls are not difficult to build but they can be manually intensive. There are two basic methods for building a retaining wall. You can use the dry wall or dry stacking method or lay up your wall with mortar. Natural stone does not require a foundation like concrete, cement blocks, bricks, or similar materials would. Natural stone using the dry stack method works well if your retaining wall is less than three feet high.
- Begin by laying out the profile of your retaining wall. If it is a straight line, use wooden stakes or concrete form stakes and string to mark out the wall.
- If the wall forms a curve, you can use a string or a garden hose to lay out the wall profile.
- You can also mark out the area using marking paint, flour, or any other white powder.
- No matter which method you use, make your marks to one side of the location where you will start your retaining wall trench.
- Dig a trench at least half as wide as your retaining wall is high and at least six inches deep. The first course of stone should be below ground.
- Place dry sand or fine gravel in the bottom of the trench, level it, and tamp it to ensure a firm foundation for the first course of stone.
Build the wall
- Cut the first stone in half using a broad mason’s chisel. Score the stone all the way around then strike the chisel in one spot on the scored line to break the stone cleanly.
- Lay the first stone in the trench. Level it both ways and tamp it firmly in place with the butt end of a block hammer or mallet. The stones’ built-in taper should cause the wall to tilt in toward the slope as you build the wall. If the stones do not have that built-in taper, adjust the stones in the trench to slope in toward the hillside.
- Lay the next stone adjacent to the first using the same method. Follow this routine all along the length of the trench until you reach the far end.
- Start the next course with a whole stone so the joints between the stones alternate. Cut the end stones on every other course until you reach the top.
- After laying the first course in the trench, backfill the trench with soil to help hold the stones in place.
- On every course after the first one, install a dead man evenly spaced. A dead man is a long stone placed perpendicular to the course extending back toward the slope to help lock the wall to the hillside.
- Install the capstones following the same method you used to place the base course of stones in the trench.
- Lay landscape cloth inside the retaining wall and up the slope a few feet. Then, backfill in behind the retaining wall.
You can spray the bottom of the trench with water to help settle and pack the bottom.
Fill in between the stones with soil so that you can plant ground cover like Vinca minor.
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