How to Build an 8-Foot Segmental Retaining Wall

Remove the soil from the area where you are building the segmental retaining wall with a shovel. Create a trench 24 inches wide, slightly longer than 8 feet and 8 inches deep for the base material.

Level the base of the trench and tamp it firmly in place, using a hand tamper. Add 6 inches of small, coarse gravel to the base of the trench. Tamp the gravel pieces together and create a level surface. The coarse edges of the gravel bind together to create a stable base.

Place the first course of six segmental building blocks on top of the gravel. Set a carpenter’s level on top of the blocks to ensure they are level from front to back and side to side. If the base is uneven, add or remove gravel to level it and reset the block on it.

Fill the trench area behind the blocks with more crushed gravel. Use the hand tamper to press it firmly into place. Use your hand to brush off any gravel that falls on top of the first course of blocks.

Break a full-size block into two pieces. Score the block at its midpoint with a chisel, and then tap one end of the block with a hammer to break it into two pieces. You might be able to purchase half blocks for your segmental wall. If you can, omit this step.

Set the half block directly over the first block in the first course. If the segmental blocks you are using have a lip on the back, press the lip of the half block firmly over the back edge of the base block. Set the remaining five full blocks in this course and finish with the remaining half block.

Tap two connection pins into the holes in the tops of the second course through to the holes in the blocks in the first course. Place one connection pin in each of the half blocks.

Fill the area behind the second course with gravel and tamp it into place with the hand tamper. Clear the blocks of any debris.

Continue building your 8-foot-long retaining wall using the preceding steps until it is the desired height. Place connection pins between adjacent courses to tie rows together. Remember to stagger all joints to give the wall additional structural stability. Backfill all of the courses except the last one with gravel. Leave the area behind the last course empty for now.

Run a bead of masonry cement on top of the top row of blocks. Set a row of capstones in place on top of the wall. The capstones cover the openings in the blocks for the connection pins and give the wall a finished appearance.

Fill in the trench area behind the final course and the capstones with topsoil. Adding topsoil allows you to seed the area behind the retaining wall with grass seed or, if you prefer, plant flowers in the area.