Project Guide

How to Build a Retaining Wall

Dig the Trench
someone using a shovel to dig a trench

The success of your retaining wall depends on a level base. To create a solid foundation, dig a trench for the first course of your interlocking retaining wall blocks to sit in, and make sure the ground remains even throughout.

  • Using a tape measure, decide the length and the width of your retaining wall, then mark off the area with the garden stakes and string.
  • Begin digging into the ground with a shovel
  • Depending on the size of your blocks, your trench should be 4 to 6 inches deep (below ground level) and have a width that’s twice the width of one block lying vertically. 
  • Once your trench is complete, compact it with a hand tamper or vibrating plate compactor.

Tip: Stay safe by wearing your
goggles and work clothes, along with protective clothing and boots, while you install your retaining wall.

Create a Building Base
a person laying concrete block to build a retaining wall base

Due to soil erosion, your retaining wall should be built on a solid foundation made from paver base. Similar to gravel, paver base is a form of construction aggregate that contains crushed rocks such as limestone.

  • Choose a paver base with landscape rocks between 1/2-inch and 3/4-inch in size.
  • Fill the trench with a 2 to 3-inch layer of paver base.
  • Use the rack to ensure the stones are evenly distributed.
  • Tamp the paver base with your tamper to make sure the foundation is evenly compacted.
Lay the First Course of Blocks
a person laying the first round of blocks for a retaining wall

It’s time to start laying your interlocking retaining blocks on the sturdy building base you just created.

  • Position your first block and use a standard level to make sure it’s even. If needed, reposition it using additional paver base and a rubber mallet to tap it into place.
  • Continue laying your first course of blocks, making sure to check that every block is level.
  • After you finish the first course, fill the space between your retaining wall and landscape with gravel.
  • Tamper the gravel to increase the wall’s stability and durability against soil erosion.
Build the Additional Courses
a person adding an additional block for a retaining wall

By installing an even first course, you’ve successfully laid the groundwork for more courses. Here’s how you lay the next levels of interlocking wall blocks.

  • Before starting the second course, cut an interlocking block in half using a circular saw, as the first and second levels of blocks must be staggered. Always wear protective goggles, gloves, a dust mask and construction-grade earplugs during this step.
  • Brush off the first course of blocks with a broom to remove any debris.
  • Lay the second course of blocks the same way as the first and finish the course with the other half of your cut block. Since the blocks are interlocking, there is no need for adhesive during this process.
  • If you wish to lay more than two courses, you only need to cut a block in half for the even-numbered courses. Following this rule will ensure your blocks are properly staggered.
  • After completing each course, don’t forget to fill the space between your retaining wall and landscape with gravel, and then tamper the gravel. 
  • Lastly, brush off the retaining wall blocks to clear away debris.

: If you don’t own an appropriate saw for cutting the blocks, you can rent one from The Home Depot Tool Rental Center.

Finish the Retaining Wall
a yard featuring a retaining wall, lush greenery and brick pavers

Lastly, put down a layer of block caps to complete your retaining wall and enhance the overall aesthetic.

  • Brush off the previous course to clean off any debris. 
  • Using construction adhesive, secure your block caps and create the top layer of your retaining wall. The block caps should overhang the retaining blocks by 1 to 1-1/2 inches.
  • Cover the gravel between your retaining wall and landscape with topsoil or sod, so your garden will grow against your wall, achieving a natural look. Complete the look with landscape fabric, if desired.

Tip: If your retaining blocks and block caps aren’t dry, the adhesive glue won’t hold properly.