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I have a small, roughly 4' by 4' retaining wall adjoining my neighbor's yard (see photos) that is leaning over and needs to be fixed or replaced. We think it has moved not because of pressure from the soil, but because of the roots of a nearby tree (visible in photo).

The neighbor is rebuilding the wall across his property that once connected with mine, so now is the time to fix the wall between us. However, we don't want to kill the tree. Could the wall be pushed back? If not, is there way way to build a new wall that minimizes the footer depth (eg use blocks?)? Or would it be less invasive to insert posts at either end and put in timber or concrete slabs to hold the soil?
yellow wall 1
yellow wall 2

2 Answers 2

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The question was bumped, so this has probably been overtaken by events. But I'll add a couple of thoughts for anyone else in a similar situation.

My first thought is to question the tree root cause. That's a pretty massive concrete wall. If it had proper footers, I'm not sure roots could tilt it. The growing roots would expand in the easiest direction, which would be into the soil. I doubt that the roots could directly push the wall out of plumb.

Tree roots do create channels in the soil for water, and it's common for roots to result in the supporting soil being eroded. If the roots are the cause of the tilting, that seems more likely.

If you really want to retain a concrete wall in that area (as opposed to say replacing it with a section of wooden fence to match what's visible in the second picture), there are a few ways to do it. One is to re-support the wall with helical piers. Another is to jack the wall back into position and get some good footers under it. Since you don't want to damage the tree roots, that can require a creative solution based on exactly where the roots are, so it wouldn't be practical to speculate here.

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I dont see that wall moving unless all the dirt is excavated from behind it, but even if you did that, it'll move right back unless some support structure was added. Either a brace or some sort of deadman.

I think the wall will be a bear to bust up and remove not even knowing what type of footer there is. Replacing it with an identical wall will require a pretty big base that should extend back beneath the backfill to prevent it from leaning again.

The easiest way my be to excavate the dirt from behind the wall and push it back to vertical. Dig a trench perpendicular to the wall and install a devised tie-back anchor securing it through a hole on the wall.

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  • Would the trench go on my neighbor's side, or my side? A landscaping company came yesterday and suggested building it with mortarless blocks. He said it could be built on top of the existing footer.
    – JCK
    Commented Sep 13, 2018 at 12:29
  • Into the dirt side, search for 'retaining wall tieback' and you'll see what I'm talking about. The blocks may work, but 4 feet is the upper limit for the smaller blocks available at HD. I've built two, one was tiered for a 5' change and the other was a bit less than 4. They both still look good, 15 years later. I'd worry about the footer being level, unless it is cut level for the blocks.
    – Gary Bak
    Commented Sep 13, 2018 at 13:44
  • Not sure about the tiebacks since they'd have to go deep into my neighbor's yard, right? It's just under 4 feet tall so maybe HD blocks will work. I'll check into it further. Thanks Gary.
    – JCK
    Commented Sep 13, 2018 at 14:37

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