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How to Build a Retaining Wall

Updated: Dec 19, 2023

Welcome back to the MAD county build. It's July 22nd, and we've got about 10-12 days left before most of our materials for framing arrive for our build. But before I can even think about the frame, I’ve got some critical work to tackle – building retaining walls. In today's blog, I’ll walk you through the process of properly installing retaining walls, a crucial step in preparing our site for construction.


A picture of the retaining wall + storm shelter all finished

Planning the Retaining Walls: The first thing to consider when building retaining walls is determining the desired finished height. It's crucial to know where you want the top of your retaining wall to be. For our project, I decided that our wall should be about four to five inches below the top of an existing wall.


The choice of block type is essential too. Depending on the kind of blocks you select, you'll need to calculate how high the wall should go to achieve the desired height. With these details figured out, I was ready to get started.


a picture of mr post frame leveling the gravel

Creating a Solid Foundation: I began by preparing the ground for our retaining walls. The first step was to level the area and compact it. This foundational work ensures that the wall will be stable and able to withstand the test of time.


I’m building two retaining walls on either side of our storm shelter, which is built beneath the garage. This setup will allow us to maximize space while avoiding potential water issues. To start, I filled the area with gravel and used a laser level to get our grade right.


A picture of mr post frame laying out the first concrete block down

With our foundation prepared, I could move on to laying the first course of blocks. This is the most critical step because it needs to be perfect. If the first course is level and properly aligned, the following levels become much more manageable.


While our wall design is relatively straightforward, it involves a slight outward angle, which I incorporated by adjusting the first layer accordingly. To ensure the blocks were level, I used a six-foot level across the back of four adjacent blocks, creating a straight guide for the rest of the wall.


Building Layer by Layer: The following courses of blocks are relatively straightforward once the first one is set correctly. One key tip is to stagger the blocks in each layer, meaning that for every other course, you'll need to cut a block to ensure that they overlap properly. This adds stability to the structure.


a picture of a excavator filling the blocks with rocks

Reinforcing with Rock: To further reinforce our retaining walls, I decided to fill the hollow blocks with rock as I built them. This method helps lock the blocks together and adds structural integrity to the wall. I plan to add approximately a foot of rock behind the retaining wall to ensure stability.


Adding Drainage for Durability: Another element I incorporated into our retaining wall construction is drainage. I installed a perforated four-inch tile along the bottom course of the wall, which slopes down and outwards. Although I haven't experienced issues with water buildup, this proactive measure helps prevent hydraulic pressure, a common cause of retaining wall failure.


As I moved up to the fourth course, I came across the need for precision cuts, particularly in the first block to accommodate our wall's angle. I used a skill saw to cut through the thick block, ensuring that our cuts aligned on both sides. Then, I gently tapped the block to break it along the cut lines.


a picture of the walls and storm shelter all finished

Finishing Touches: With our retaining wall rising layer by layer, I'll fill the cavities with rock and backfill with dirt as I continue. This ensures that the wall remains stable and well-supported. Finally, I'll cap the retaining wall with 53-pound caps, providing a polished finish to our retaining wall.


Our journey to build our dream home and garage is well underway, and constructing these retaining walls is a pivotal step in securing the foundation of our project. We're excited to see the progress, and I’ll keep you updated as I move forward. Stay tuned for more updates on our MAD county build!


Thank you,

Mr Post Frame



a picture of Mr and Mrs Post Frame

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