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I have a poured basement foundation on a 1920s home in the pacific northwest (zone 8). We've had a few cold winters, and there are signs of frost heave in the concrete around the house. The walkway, for instance, is all busted out and unlevel.

More urgently, I noticed recently the basement wall is pitched inward, about 1/2" per 4'. Also the forms are not totally level. I did not notice this before (lived here 6 years). Yet, I did not see any evidence of shear or stress fractures in the foundation. there are no cracks or signs of stress. Also the interior walls are not pitched at all.

Is it possible the house has settled with some geologic movement? Or the original pour is off? Is this any sign of danger, and what remediation would be considered?

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  • Concrete does not bend well so if no cracks, then the pour being off a bit is possible. Would check carefully for cracks, frost heave and settling usually lead to cracks, some quite small.
    – crip659
    Oct 25, 2023 at 19:29
  • Are you saying it was plumb but not anymore
    – Traveler
    Oct 25, 2023 at 19:55
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    It's 100 years old. If the outside of the basement wall slopes, but the inside does not, (which is what I read you to say) it was built that way, and has been that way for 100 years, so it's not "urgent" because you noticed it.
    – Ecnerwal
    Oct 25, 2023 at 20:50
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    Can you see the sill and joists? Is the sill still connected to the foundation solidly? It seems unlikely that the wall would have come more than an inch out of true without impacting some structural elements.
    – Jon Custer
    Oct 25, 2023 at 20:50
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    re: "Is it possible the house has settled with some geologic movement?"; it's not possible, it's virtually guaranteed, though on a lesser scale than geologic. An inch or so through the wall is fine: as long as some of the bottom of the thick wall overlaps some of the top, it normally won't buckle. 90% of houses aren't plumb; new ones because of chincy foundations, old ones because wind, rain, frost, and age guide long-term unpredictable slow settling.
    – dandavis
    Oct 25, 2023 at 22:30

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Your pitched foundation wall was probably placed out of plumb. For your problematic concrete flatwork, frost heave is very unlikely the cause in USDA zone 8. Expansive soil, heaving from roots, and installer negligence (like leaving a layer of organics below placed concrete) are more likely root causes.

Expansive soil (or frost heaving soil) doesn't uniformly expand along a whole foundation. There are good spots and bad spots. The differential expansion along the whole foundation causes localized damage analogous to your problematic flatwork's damage.

I have seen earthquake induced liquifaction cause foundation failures, where you could see rigid body movements without localized damage like you've described. It's saturated soils with liquifaction potential, however, so the tiny probability of soil liquifaction being the cause of your pitched wall goes to an even tinier probability if you don't have a high water table.

Go to the corner where your pitched wall meets a perpendicular wall. If your wall has pitched after the concrete was placed, then you should see a wedge-shaped gap at the corner. If there's no such gap, then your foundation wall was probably placed out of plumb. It was probably placed out of plumb.

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