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At the back of my property there's a concrete retaining wall that separates my back yard from my neighbor's. The wall has several enormous cracks and is leaning, especially toward one side. I'd guess the wall has been here since the house was built in the mid 1950s

To my novice eye, the leaning/cracking seems due to a larger tree in the corner of my neighbor's lot. Since we moved in to the house about 7 months ago the wall has been stable and went through winter and Oregon rains just fine. No idea how long it's been like this. There is evidence that a fence used to be against this wall but it has been removed.

What's the right course of action? Replacing the wall entirely seems like it'd be very expensive. Is there a sensible alternative? Is there a danger of the wall failing and taking some of my neighbor's yard and the tree down with it?

Pictures of the wall are here: https://imgur.com/a/gMAdd

  • Looks like this wall has two tiers and the bottom tier is doing fine? What is the rise and run of each tier? What sort of soil is the wall holding back (Clay, sand, mix)? If there is enough room the tree could be saved when the wall is replaced. – Stanwood Apr 14 '18 at 11:23
  • Where is the property line with respect to the failing section of retaining wall? It sounds like the top wall is on your neighbor’s property but the tree may land on you if it fails. That’s a tricky problem. Look up the book NOLO Neighbor Law (my library had a copy). Will give you some important background on the legal issues involved if this turns into a dispute with your neighbor. – Stanwood Apr 14 '18 at 11:29
  • Yes, there are two tiers and the bottom tier is in fine shape (although it needs a good power washing). Each one is about 3 feet tall -- the top of the second tier (below the metal fence) is about eye level for me and I'm 5'10". Not 100% sure about the soil. It seems like it may be sandy or a sandy mix judging from digging down into my yard. – Nathan G Apr 14 '18 at 20:59
  • That's also a great point about the legalities. I'm not really sure if the concrete wall is my responsibility or shared responsibility. The metal fences around the property seem to be shared responsibility, but it could be that also includes the rear retaining wall. – Nathan G Apr 14 '18 at 21:01
  • In many (most?) U.S. jurisdictions a boundary fence/wall is joint property. Both sides have rights and responsibilities to maintain. But it can matter if you are “making use” of the wall and some other details. The NOLO book gets into that. I’m not sure how a tiered wall is treated but you can be sure there is some precedence. – Stanwood Apr 14 '18 at 21:37
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You have several issues: 1) Diagonal cracks, 2) Deadman movement, 3) Tree root stress, 4) Fence movement, 5) Water buildup behind wall.

1) Diagonal cracks are an indication of wall stress load failure. That is to say, the wall is failing because of an excessive load on the wall and a lack of reinforcement in the concrete wall to resist the load. (Vertical cracks are an indication of temperature or expansion failure...which is much easier to fix.)

2) Most alarming is the fact that the steel plates with the steel rod and bolt is called a deadman and it’s failing too. Evidently a deadman was installed in at least two locations (that I can see) to help hold the top of the wall from tipping over. If you look close, you can see a gap (space) between the steel plate and the concrete wall. This is an indication that the deadman has failed. Perhaps the rod has come loose from the deadman. The deadman is doing nothing.

3) Yes, probably most of the “load” on the wall is from the tree. Of course as the tree grows it spreads out and “pushes” on the wall. However, as the tree sways from the wind, the tree roots “push” on the wall too. The tree needs to go...

4) Any movement from the fence will add stress to the wall too...similar to the tree in Item 3) , above.

5) water is heavy and puts tremendous stress on a wall if it’s not collected and drained away...especially in a climate like where you live. When you have many inches of rain in a short period time the subterranean water doesn’t have a chance to dissipate. When it builds up against the wall, that’s a lot of stress.

I don’t know of a way to save the wall. It will continue moving until it falls. You could slow the failure by removing and killing the tree. However, be careful when the tree falls, it could put a huge thrust on the wall.

BTW, I wish I had a Bronco to go 4-wheeling...

  • Thanks for the detail! Interesting about the failing deadmans. Do you know of a good resource to look more into how those work? I'm not looking forward to having that kind of conversation with my neighbor about that tree. It's also a lovely tree! What do you think the safest way to replace the wall is? Do you think it would be possible to replace the failing part? Trying to get some engineers out to look but want to be able to have an informed discussion. Thanks! – Nathan G Apr 14 '18 at 21:08
  • Deadman didn’t work before, I doubt they’ll work now. You’d need your neighbor’s permission to dig up their property anyway. We’ve “bound” the roots of trees with steel bands to restrict their growth, and it only lasts for 10-15 years and then the roots are a problem anyway. I’d encourage you to remove the tree AND kill the roots. I’d remove the wall and replace it with a “stacking block” retaining wall. They’re much cheaper than a poured-in-place concrete wall and you could do it yourself. You can go 4’ high without engineer report. I’d get your neighbors WRITTEN permission before you start. – Lee Sam Apr 15 '18 at 2:13

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