Building a retaining wall can be a great way to prevent hills from sliding and shifting, as well as providing an additional landscaping level around your home. Properly built retaining walls can increase your property values as much as they can improve your curb appeal.

You may already have a concrete slab on your property, and might wonder if it is a suitable location for a retaining wall. However, there are some considerations to keep in mind. While a retaining wall can be built on a concrete base, you will need to do some preparation to the slab to ensure it is strong enough.

Improperly prepared concrete bases can cause damage to your retaining wall over time, including misalignment, cracking, breaking, and eventually collapsing. Let’s take a closer look at ways you can use an existing concrete base to build a retaining wall on, while ensuring it remains strong and stable throughout the years.

Adjusting an Existing Concrete Base

If you already have an existing concrete base and want to place a retaining wall on top of it, you will need to do some re-building of the slab. This slight adjustment to the concrete base will ensure the retaining wall does not crack or break throughout the different seasons.

You will start by breaking away some of the existing concrete slab. The idea here is to create a trench that you can place horizontal rebar into. Once the rebar has been placed, you will pour concrete on it as the actual retaining wall foundation.

From here, your goal is to build up the retaining wall by placing cinder blocks onto the wet concrete that is over the horizontal rebar. You will then be adding vertical rebar through the centers of the cinder blocks to help reinforce it.

The purpose of having to rebuild some of your existing concrete base with rebar reinforced concrete is to help the retaining wall remain strong and can flex without breaking during the changes in temperatures and seasons.

Deciding on a Foundation

Once you have your trench laid out in your existing concrete base, you will need to decide on a foundation before placing the cinder blocks. Most people will opt for a simple mix of sand and gravel. This is an effective and cost efficient foundation to use with retaining walls.

Other foundations can include all gravel, all sand, polymer sand, and packed soil. Regardless of your foundation choice, in order to keep your loose foundation effective, it’s important to place a landscaping cloth over the top. This will help prevent erosion on the packed foundation.

Regardless of your foundation type, be sure to evenly stack your bottom stones or blocks for the retaining wall. These are the most important placements and will help determine the stability of the rest of the wall. This first layer of stones or bricks should be just below the grass line. Further stones or bricks should be placed in a staggering method to help interlock the wall together and make it much stronger overall.


A retaining wall can be placed on an existing cement base, but will need some adjustment in order to be viable over the long term. Building a retaining wall directly onto an existing concrete base will not give you the many years of longevity you want when it comes to a retaining wall.