How do you build a block wall?

To build a block wall, stack rows of interlocking retaining wall blocks on top of a layered base, and backfill the wall with crushed gravel for support. Contact a building code administrator to ensure the area is structurally sound and free of underground utility equipment.

1. Dig a trench

   For a 4-foot wall, dig a trench that is 7 to 9 inches deep and 24 to 28 inches wide. Set the soil aside for later use. Place a block at the front of the trench and a few inches back, and ensure there is at least 12 inches of open space behind the block.

2. Flatten the base

   Use a tamper to flatten the base.

3. Mark the base for the layered materials

   Attach a 4-foot level to a long 2-inch by 4-inch board. Start at the bottom and measure up. Measure the first 4 to 6 inches of the height of the base, and use the level and a stake to mark the top of the height. Measure 1 inch higher than the first stake, and use the level again to mark the height.

4. Install a compacted base

   Pour class V crushed base material in the trench. Tamp the base until it is flat and flush with the top of the first stake.

5. Install a layer of sand

   Pour sand on top of the compacted base. Use a screed board and a hand trowel to level the sand to the top of the second stake.

6. Install the first brick

   Lay down the first brick, and secure it with a 3-pound sledge hammer.

7. Install the first row

   Run a masonry string along the back of the first brick. Install the rest of the first-row blocks along the string. Ensure the row is level lengthwise by using a 4-foot level, and use a torpedo level to make sure the row is level widthwise.

8. Install the soil

   Pour the soil from earlier in front of and behind the first row. Pack the soil until it is ground level.

9. Install the remaining rows

   Lay the second row of bricks on top of the first row with a 3/4-inch offset from the front and a 4-inch overlap at the vertical joints. Hammer the pins into the holes, and hammer a center pin below the surface of the blocks. Repeat with the remaining rows.

10. Fill the back

    Pour crushed gravel in the space behind the wall until it is flush with the top row.

11. Install cap blocks

    Apply two lines of concrete adhesive on one of the top row blocks. Install a cap block on top of the block. Repeat with the remaining blocks of the top row.