How to Use Concrete Blocks for Retaining Walls
- 1). Remove the soil from an area in front of the hill, digging a trench that is 4 to 6 inches deep and 24 to 28 inches wide. Screed the bottom with a piece of 2-by-4-inch timber to make sure it is even and straight.
- 2). Dig back another 12 inches behind the previously excavated area to create a backfill area for gravel. The gravel installed behind the wall will provide water drainage.
- 3). Pour 4 to 6 inches of gravel at the base of the wall area. Compact the gravel using a tamper so it is 1 inch below the top of the excavated area.
- 4). Add a layer of sand to the gravel base. Wet the sand. Run a 2-by-4 along the sand to make it smooth.
- 5). Set two wooden posts at the edges of the installation area and run a string between them. The string makes a straight line to install the block along.
- 6). Place the first level of concrete block underneath the string line. Place a 4-foot level on the top of the blocks to determine whether it is level. Lightly hit the concrete blocks with a rubber mallet to make them even.
- 7). Place the next course of blocks onto the first layer. Stagger the blocks like brickwork.
- 8). Drive metal rebar in through the holes in the concrete block. Drive in two pins per block. Place another pin on top of the installed pin and tap the two pins with a hammer to set it slightly below the top of the block. This prevents the pin from interfering with the next level.
- 9). Fill in behind the wall with gravel as you build the layers.
- 10
Place a 1/4-inch bead of concrete adhesive on the top block of the wall. Place cap blocks on top of the adhesive to finish the wall.
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