Leveling a retaining wall


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Old 06-03-20, 10:46 AM
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Leveling a retaining wall

I spent a lot of time researching building retaining walls on my own. My wall is eventually going to be about 40 long and 24-30 high using concrete blocks. So I had a ton of gravel delivered, dug a trench (about 8 deep), tamped down the earth and then layered the gravel. While I didnt have a plate compactor, I used a 10x10 tamper to level off the gravel. I then put down my first course of blocks, making sure each one was level on all directions by using a 16oz. rubber mallet.

Before laying down all the first course, I did about 15-20 and built up from there to get a sense of how high we wanted and how it all looked. Love the look, however Im finding that even though the first course was level, Im starting to get off level, mostly front to back. Not a ton but the bubble is no longer centered. Im wondering if this is a common issue and how to deal with it. Perhaps things are settling with the weight of the blocks or some of the blocks arent quite uniform. Regardless, if I find this can I use something like leveling sand to make slight adjustments as I grow the wall? I could always pick up Any other suggestions?
 
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Old 06-03-20, 11:43 AM
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How thick is your base? You mentioned an 8" deep trench but didn't say how much stone you put in. A ton of stone isn't very much so it's possible your base layer isn't thick enough. 6" thick after compaction is the minimum I do for any wall no matter it's size.

You might be seeing some poor compaction of your base material. It really is difficult to achieve the same compaction by hand as you get with a plate compactor. As you build up drop/place blocks and move them about it could be pressing down unevenly into your base causing the wall to move a bit.

It also could be that your first course is not as level as you thought. It doesn't have to be perfect but the closer to perfect you can get the better. You can use a rubber mallet or dead blow hammer to correct somewhat as you build your wall by driving the high side of the base blocks a bit lower until your wall is vertical again. Easy movement of the wall at this point should be a warning to how easily it could shift or move as the wall ages.
 
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Old 06-04-20, 11:36 AM
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Hey Pilot - thanks for the input. The trench is 8", 3" of gravel so that's probably the issue. Somehow I thought I heard 3" was enough, apparently enough.
 
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Old 06-04-20, 02:16 PM
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So a 30" tall retaining wall is getting up there, you mention "using concrete blocks" what kind of blocks are your using?

 
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Old 06-05-20, 06:27 AM
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They are from HD - 4x11.75x6.75 Pavestone (#81100).
 
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Old 06-05-20, 09:38 AM
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I would not use those blocks for a retaining wall. They are OK for decorative, light duty edging or maybe a very short retaining wall but they just don't have enough mass and size for longevity.

These are the blocks I use for retaining walls. These are proper, structural retaining wall blocks engineered for holding back earth. There are other brands but they all are much larger and heavier. These use heavy duty fiberglass pins to lock the rows of blocks together. The larger footprint provides a larger bearing surface on your crushed stone base. Their mass (85-120 pounds empty) per block allows them to stay in place and resist bumps from cars and lawnmowers.
 
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Old 06-05-20, 09:54 AM
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That was my concern, those tapered stones are maybe good for 18" but not suitable for anything higher. As PD mentioned they really dont have the mass to support a wall that high.

To be honest even the ones PD has shown are a bit light.

Ive made many a 3' retaining wall out of 18-24" boulder and feel very confident they will be around for many years!
 
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Old 06-05-20, 11:16 AM
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Good stuff guys, I appreciate all input!
 
 

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