How to Build a Block Foundation Wall

What You'll Need
Masonry chisel
Drilling hammer
Carpenter's level
Chalk line and line level
Protective goggles
Retaining blocks
Landscape fabric
Leveling sand
Wood stakes

A concrete block foundation can be used as a soil retaining wall or to emphasize a colorful flower garden, the peace of a garden waterfall or a section of well manicured lawn. With the right block shape and color and a few simple tools, you can have your block wall set up in no time.

Step 1 – Measure and Stake Out your Wall Boundaries

Using your string and stakes, mark the outside boundaries of your wall. Locate each stake within 10 feet of the next one to keep the string taut between them. Tie the string to each stake to keep it from being blown off the stake.

Step 2 – Create your Foundation Trench

Dig a 4" trench, beginning at one end of the area where your wall will be built. Remove sharp or protruding rocks from the soil at the bottom of your trench, tap the soil on the floor of the trench, pour enough sand in the trench to cover the bottom with about 2" of leveling sand, then tap the sand.

Step 3 –Lay your Blocks

Place your first block on the floor of your trench, beginning at one end of the trench. Use your level to be sure the block is level. If it is not level, try tapping it with your hammer. But be careful to avoid breaking or chipping the block. If you are unable to level the block by tapping, remove it and level the sand on which the block was resting. Lay additional blocks, end to end, leveling each block to be sure all blocks are of an equal level.

Step 4 – Place your Line Level

As a guide line to set your block row level, lay a block at each end of your block row and set your line level on these two blocks. This level will serve as a guide to level the next row of blocks. Saw a block in half, and lay one half of the block at each end of your second row level. This placement will allow you to stagger the position of blocks on this second row so that each block on this row spans the ends of the blocks in the foundation row beneath it. The bottom blocks are supported better using this method. Finish laying blocks in the block row above the foundation row, following the same procedure as in the second block row.

Step 5 – Fill with Soil

Lay your landscaping fabric out evenly against the back surface of your wall. This will prevent soil and water from seeping through cracks between the blocks when this space is filled. Fill the space behind the fabric with soil. When finished filling, trim away any exposed edges of the fabric.

On the surface of the top block row, use mulch or decorative stone for a finishing touch.