To build a concrete block retaining wall, dig a trench, stack and secure the concrete blocks, and add capstones. This procedure takes about two days and requires a measuring tape, wooden planks, gravel, sand, concrete blocks, capstones, concrete adhesive, work gloves, metal pins, a hammer, a level, a rubber mallet and a shovel.Continue Reading
Measure one of the concrete blocks. Dig a trench that is 1 foot wider than the block and 6 inches deeper. Tamp on the bottom of the trench to compact the soil, then add thin wooden planks. Cover the planks with 6 inches of gravel and sand, compact the fill and add another 2 inches of sand.
Stack a single layer of blocks in the trench, starting in the middle. Drive each block into the sandy foundation by hitting it with a rubber mallet. Use a carpenter's level to verify that the blocks are even. Place a second row of blocks on top of the first, staggering the edges of the blocks.
Drive metal pins down through the blocks with a large hammer. Pin each row of blocks before you lay the next.
Stop laying blocks when the wall reaches the desired height. Lay gravel behind the wall so no empty space remains in the trench. Tamp down the gravel so it is level with the surrounding ground.
Dab the top of the wall with concrete adhesive, and set capstones on top. Drive them down into the adhesive with a rubber mallet.