How to Build a Retaining Wall With Manufactured Blocks

A retaining wall is an inexpensive, decorative way to level a slope on a property or create a garden space. Because they interlock and are uniform in shape and size, manufactured blocks make building a retaining wall a bit easier than natural materials, although the job still requires some heavy physical labor.

Instructions

Difficulty: Moderately Challenging

Things You’ll Need:

• Gloves
• Safety glasses
• Back support
• Flat-pointed shovel
• Retaining wall blocks
• Tape measure
• Wood stakes and string (or a garden hose)
• Carpenter's level
• Mason's line
• Line level
• Hand tamper
• Leveling sand
• Gravel
• Chisel
• Hammer
• Landscape fabric

1. Mark the space where you want to build the retaining wall. Outline the shape using stakes and string or a garden hose.
2. Choose the blocks you want to use. You'll need to know the size of the blocks you'll be using before you can figure out how many blocks are needed for the project.
3. Call your municipality to find out if a permit is required to build a retaining wall. Also ask for the contact information for all local utilities. You'll need to call them before you dig as they will need to mark the location of underground lines in the area of your proposed wall. Often this can be done with one phone call instead of calls to multiple utilities. If you can't find this information, then call each utility individually.
4. Dig a trench a little wider than the block width and four to six inches deep. Be sure the foundation course is below ground level. Tamp, level the bottom, add a one- to two-inch layer of sand or paver base, and tamp it down again.
5. Place the first block in place and check it with your level. Use a hammer to gently adjust the block if it is not level. Continue laying blocks. Be sure each block is level; adjust if needed.
6. Score a line on the center of a block, then place the chisel in the center of the line and strike with a sledgehammer to cut it in half. This is the first stone of the next course. It must be cut in half so that the wall will have a staggered look. Set the stone in place on the end of the second course and interlock with the foundation layer.
7. Move to the other end and place another block on the foundation layer. Run a string between the two blocks and check for level using a line level. If the string is not level, adjust the foundation course.
8. Lay the second course by interlocking the blocks with the first course, making sure they are level. Cut the last block on the row in half.
9. Fill the trench around the foundation wall with soil and tamp it well.
10. Continue to place the rows of blocks. Cut the first and last blocks of every other row in half to be sure the rows are staggered.
11. Place landscape fabric behind the wall and a few feet up the slope. This will prevent soil from seeping through the wall. Backfill behind the wall and tamp the dirt. If the wall is higher than two feet, fill the area closet to the wall with gravel.

Tips & Warnings

• Manufactured interlocking blocks should not be used to build walls higher than 15 to 28 inches. For a slope higher than this, consider adding a series of low terraces rather than one high wall. Consult the block manufacturer's instructions about height limits.

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