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I have a two-story home built in the mid-1970s. In the process of replacing a door upstairs several years ago, I realized how far out of plumb the upstairs interior wall is. Over the 79" from floor to doorway header, it is ~7/8" out of plumb. Unless I am mistaken, it is a load-bearing wall. It runs the length of the house underneath the peak of the roof; below it is a similar wall on the first floor and supporting columns and masonry in the basement.

At the time I was thinking about the practical hassle of installing a door in such a situation, but recently the concern of structural integrity has popped into my head. I suspect it's a non-issue, but: does a wall this far out of plumb cause any issues as far as transmitting load downward? Rather than being directed straight downward, the wall passes the load slightly horizontally as well.

To my knowledge, this hasn't shifted in the decade or so that I have lived in the house, so probably everything is just fine. But...it's on the back of my mind, and I thought I would ask those who may know. What signs of trouble might I be looking for...or is this really just a non-issue?

Edit: additional, clarifying details: First floor walls (both parallel exterior and the interior wall below) are reasonably plumb. The house is a saltbox, so there is only one parallel exterior wall on the second floor - it is out of plumb in the same direction as the upstairs interior wall, although quite a bit less so (1/4" to 3/8" over the same vertical distance, depending where I measure). Both walls are leaning in the same direction as the longer roof side does, if that matters.

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  • Do the exterior walls running parallel to this interior wall have the same out of plumbness? Or are they nice and vertical (be sure to sample multiple positions for each wall)? And I assume that the interior wall below is plumb? Is that right?
    – popham
    Jan 24 at 6:59
  • @popham, I have updated my question with this information - interior wall below is plumb, although second floor parallel exterior wall is not perfectly plumb Jan 24 at 14:10
  • That 5/16" is pretty reassuring. You might also check the ends of the interior wall and the ends of the parallel exterior wall for plumbness. The theory being that the walls were plumbed at the corners as they were locked in place with fasteners to the perpendicular wall. If they're plumb, then the optimistic theory is that the roof and ceiling have locked in out of plumbness dating back to the home's construction. If there's no ceiling and roof sheathing has been replaced, then that was an opportunity to lock the walls out of plumb.
    – popham
    Jan 24 at 17:09

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There's no structural problem with that level of out-of-plumbness. Its root cause could be a structural problem, however. If the exterior walls don't have the same issue, I would attribute the wall's plumbness to poor workmanship and not a developing structural problem. Even if the exterior walls do have the same issue, there's a laundry list of bad workmanship checks I would do before exploring structural possibilities.

To contextualize the pushover moment caused by this defect, I hypothesized a single story, 30 ft wide home with your out-of-plumb load bearing wall under its ridge and with 8 ft exterior walls under its eaves. I'll compare the out-of-plumb wall's pushover moment to a coarse approximation for that of a 25 mph wind.

A load bearing interior wall gets 50% of the roof load with the remainder going to the exterior walls. Assuming 5 psf ceiling, 10 psf roof, and 20 psf snow on the roof (equivalent to about a 30 psf ground snow load), I get a pushover moment of (7/8")(5psf + 10psf + 20psf)[(0.5)(30ft)] = 460 #-in/ft.

For a 25 mph wind, I get a pushover moment on the 8 ft tall exterior wall of

(0.00256psf/mph2)(25mph)2(8ft)(8ft/2)(12"/ft) = 610 #-in/ft.

This indicates that your out of plumb wall is structurally equivalent to about a constant 25 mph wind against the hypothetical house.

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  • Hmm...I don't know whether to be relieved or concerned by the idea of a constant 25 mph wind! :) In my time living here I have noticed a number of items that make me annoyed with lazy/sloppy/hasty workmanship in the past - are there specific indications of bad workmanship that you might look for as far as the out-of-plumb goes before more seriously considering structural possibilities? Jan 24 at 14:14

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