Build a Cinder Block Retaining Wall

Lead Image
  • 20-30 hours
  • Advanced
  • 3,000-9,000
What You'll Need
Cinder blocks
3/4-inch PCV pipe
Hacksaw (for pipe)
Gravel or small stones
Pre-mixed cement mix

Impeding slopes and erosion can be serious obstacles to landscaping and construction. If you need to create a stable, level ground from a grade, or if you have a sheer section that is subject to erosion, you can benefit from a cinder block retaining wall. With a little engineering and a minimal amount of work and supplies, you can build a retaining wall to suit your needs.

One of the best parts about this project is its simplicity. The blocks are arranged with mortar, so there are few tools and little expertise necessary to complete the wall. The key to success with this project is adherence to some simple engineering principals. Here are some simple steps that you can follow to make a sturdy retaining wall of your own.

Disclaimer: It is important that you check your local building codes before you begin construction of your wall. Many cities will require a permit for a wall over 3 feet high. Walls that are less than 3 feet high are likely exempt, but it is still a good idea to check.

Step 1 – Dig Out the Work Area and Foundation Ditch

Although this wall will not require mortar to bind the blocks, you will need to create a concrete foundation. In order to do this, you must dig the slope back away from where the actual wall will be constructed. Once the area is clear, dig a ditch about 1 foot deep and twice the width of the blocks under where you want to put your wall.

Step 2 – Create the Foundation and Reinforcement

To ensure your wall is able to hold back the extreme weight of the earth that you wish to retain, you will need to reinforce it with rebar embedded in a concrete foundation. The rebar pieces should be just about the height of the wall, and they should be bent in an L-shape at one end.

When putting them in place, you should make sure that they are lined up with each other. Place them with the end of the L-bend facing out from the wall and the long end sticking up from the concrete, about 1/4 of the width of the foundation from the wall. In other words, when you are finished, a line of uniformly tall rebar should be protruding from the foundation about 1/4 of the way to the back.

The rebar posts can be between 2-3 feet apart depending on the desired strength. Fill the concrete in about 10 inches deep. You will likely need to use wooden blocks to keep the rebar in place until the concrete is dry.

Step 3 – Install the Drainage Pipes

One of the most crucial aspects of the retaining wall is drainage. Water retention in the earth can lead to water damage that could destroy your retaining wall. In order to prevent this, you will want to install short lengths of PVC pipe through the base of your wall; this will allow water to drain.

You can do this by laying the first layer of cinder blocks with pieces of 3/4-inch PVC pipe between some of them. Use lengths of pipe that are as long as the width of the blocks so that the holes are flush with each side of the wall. They should be about 2-3 feet apart and just above the level of the ground in front of the wall.

Use the mortar to stick the pipes in place. The blocks must be placed with the rebar stakes sticking up through their hollow centers. Make sure that the inside of the back of the cinder blocks are placed against the rebar, so that it will absorb force from the earth being held back.

Step 3 – Build the Wall

This part might seem simple, but it will take care and discipline to accomplish. You might want to practice this a little bit before you try your final project. It is important not only aesthetically, but also structurally that the brick and mortar be placed evenly.

Step 4 – Fill in the Ground

Once the mortar is dry and your wall is completed, it is time to fill in the space behind it. You will want to use large gravel or small stones to fill it up above the level of the drainage pipes. Once this is done, simply fill in the rest with dirt.

If your cinder-block retaining wall is ever damaged, you can easily fix it by making repairs. For a lot less money than it would take to hire a construction crew, you have now created a retaining wall that will hold your landscape for years.