Introduction: How to Build a Block Retaining Wall
I had an area on the side of my house that was a narrow path of flagstones and sloped down toward my neighbor's house. The space was pretty much unusable for anything except walking by. I decided to build a retaining wall on the property line, and raise up the ground to be level so I could reclaim this part of my yard and improve the look of my property. It's important to note that I've never built any type of wall before so this was my first attempt and I'm really pleased with the results.
This project used about 165 blocks, 30 bags of gravel, and my finished wall was 39 feet long. The total cost came in around $1,200. It took me around 80-90 hours to build from start to finish.
Step 1: Tools and Supplies
Step 2: Getting Started
A word of caution before we get started: The vast majority of time spent working on this wall was measuring, re-measuring, leveling, and measuring again. Stacking all the blocks once everything was measured took about 1 hour.
Your very first steps should be to decide where you want your wall, and place stakes accordingly. Run your mason line tightly between your stakes and hook your string level to it to be sure it's level. Double check this, because you aren't going to want to redo this part later on. Measure your block front to back. Then dig a trench about 3 inches bigger than that. You will need to make sure you have room for gravel in front and behind your blocks to allow water to drain. Dig your trench deep enough to allow you to put 1-2 inches of gravel while still leaving your first row of blocks partially buried. My blocks were 4 inches high. I dug a trench 4 inches deep and filled it with 2 inches of gravel. Then I packed the gravel down using a hand tamper. This left my block 2 inches below the ground. You can see from the photo that I also have gravel in front and behind the block.
Step 3: Prepare Your Block
The blocks I used were interlocking. They had a lip on the back that is meant to grab the back of the block below it and keep it from sliding forward. This gives the wall strength and allows it to resist being pushed over by the weight of all the dirt behind it. The bottom row of blocks is much easier to level and move around if this lip is removed. Use your pick to chip off the lip for each block that will be resting on the gravel.
Step 4: Level Your Block
Once you've laid your first block onto the packed gravel, lay your torpedo level on top of the block. It won't be level. Add and remove gravel from under your block until you are level. If you're off by just a tiny bit, try banging the top of the block with a rubber mallet. The first block I leveled took me about 10 minutes. After the first few it got a little quicker. Double check to be sure your block is perfectly in line with the string. In the third photo you can see the string lined up with the back of each block. I later changed my method to lining it up with the front of each block because the wall looked straighter that way.
Step 5: Add Blocks
Most of the time building your wall will be spent on this step. Place the next block (with lip removed) down alongside the one you just leveled. Use your torpedo level on the edges of the two blocks to determine whether your new block is too high or too low in relation to your nicely leveled block. Add or remove gravel until the two joining edges are at the same height. (Photo 1) Then place your level on the center of the block and add or remove gravel until it is level. Check the edges of the 2 blocks again to make sure they are still even with each other. If they are, congratulations! Go back to the beginning of this step and repeat until your wall is as long as you'd like it to be.
Step 6: Stepping Up
As you continue to place and level your bottom row, you may notice you need to dig deeper and deeper to place a block that's level with your previous one. If this happens, you might want to consider stepping your wall up. (or down, depending on your landscape) To do this, stop your row and put gravel around the block. Instead of placing your next block alongside the previous one, place it on top positioning it exactly halfway. Fill underneath with gravel and level this new higher block. Then continue as normal.
Step 7: Moving Along
Once your first row is complete, straight, and level, fill the empty space behind your wall with gravel. Now lay your landscape fabric on top of your block and place your second row of blocks on top so they hold the fabric down. Make sure you stagger the blocks.
Step 8: Gravel/Dirt
Place gravel against your wall inside your landscape fabric until it almost reaches the top of your wall. Then place dirt on the other side to bring up the ground to the same height. Once they are even you can place the next row of bricks. After that row is complete, repeat your gravel and dirt filling.
Step 9: Caps
If you want your wall to have a finished look, you will want to add caps to the top. Caps are just a solid concrete block with no lip that you will glue with adhesive to the top of your block.
Step 10: DONE!
Now's the time to step back and admire your work! If you have any questions or tips, please feel free to add them to the comments.
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