Retaining walls create a flat space for a garden bed, patio or hedge; they also prevent erosion. Retaining walls are used to manage steep slopes on a landscape; however, they are not limited to sloped yards. They also add the illusion of a slope on a flat yard. Interlocking block requires no mortar. Interlocking blocks come in many styles and colors that will blend with or provide an accent to your landscaping.
Things You'll Need
- Excavator or shovel
- Line level
- Utility knife
- Landscape fabric
- Compactable gravel
- Tape measure
- Plate compactor
- Interlocking block
- Perforated drain tile
- Hand tamp
- Construction-grade adhesive
Excavate the slope on your lawn to create a level area for the retaining wall using an excavator or shovel. While excavating, allow at least 12 inches of space for the gravel backfill between the back of the wall and the slope.
Mark the front edge of the wall at the ends, corners and curves using stakes. Pound the stakes into the ground using a hammer. Connect the stakes with string using a line level. Adjust the string if necessary until it's level.
Dig a trench for the first row making it 8 inches deeper than the thickness of the retaining wall blocks. As you work, measure down from the string to verify the trench remains level.
Cut landscape fabric using a utility knife into strips 3 feet longer than the planned height of the wall and line the excavated areas with the landscape fabric. Overlap the strips at least 6 inches.
Spread a 6-inch layer of compactable gravel into the trench using a shovel and tape measure. Compact the gravel using a plate compactor according to the manufacturer's instructions.
Lay the first row of blocks into the trench. Align the front edges with string. Check the blocks frequently as you go with a level, and adjust them if necessary by adding or removing gravel.
Lay the second row of blocks according to the manufacturer's directions. Make sure to stagger the joints with the course of blocks below and check as you go that the blocks remain level.
Add approximately 2 inches of gravel to create a slight downward pitch.
Place perforated drain tile on top of the gravel added in Step 8, about 6 inches behind the blocks. Make sure the perforations face down. Verify one end of the pipe is unobstructed, as runoff water cannot escape it if it's obstructed.
Lay the additional rows of block until the retaining wall is approximately 18 inches high and has offsetting vertical joints in straight rows.
Fill behind the wall with course gravel, packing it down as you work with a hand tamp.
Lay the remaining rows of block, except the top row, backing filling the wall with grave and tamping it down with a hand tamp as you work.
Foil the landscape fabric down over the gravel backfill. Add a thin layer of soil over the fabric, light packing down the soil with a hand tamp. Fold excess fabric back over the tamped soil.
Apply construction adhesive according to the manufacturer's directions to the top blocks and lay them in place.
Fill in with soil behind the wall and the trench at the base of the wall.
Add sod or plants if desired above or below the wall.
Tips & Warnings
- Limit the height of retaining walls to 4 feet. Taller walls require special building techniques and permits because they are subject to thousands of pounds of pressure from the weight of the soil and water.
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