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Is my foundation moving?

user-6758514 | Posted in Green Products and Materials on

My wife and I are having a net zero slab on grade house built on very sandy soil.  Foundation, built October 2019, is 4″ reinforced concrete on 7″ high density EPS on 3″ compacted base with compacted (sandy) fill below that; preconstruction grade was gently sloped.  Many of the windows are Thermo Tech Northern Exposure triple-pane casement windows, installed in January.

On a recent visit to the house, we discovered that with some but not all of the casement windows, the locking mechanism takes a great deal of force to operate.  Unfortunately, we aren’t sure how well they operated right after installation; those we operated were fine, but we didn’t systematically test them all, and don’t know whether the installer did. 

We were concerned that this observation about the windows might reflect settling of the house/foundation.  General contractor has taken a look and says that there is no evidence of settling.

Question is whether this phenomenon with the windows could be due to settling, and that it might be more sensitive to settling than anything else one would look for as a sign of settling.

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  1. Expert Member


    If your window are installed in wood frame walls with exterior sheathing providing a shear-plane, unobservable settling of the foundation would not make any difference to their operation. The problems with the operation of your windows are due to something else. My first guess would be excessive insulation around the perimeter of the openings used for air-sealing, or wet framing.

    Uniform settling of the house would be unnoticeable, almost unheard of, and cause no real effect. Differential settlement would first cause visible cracks in the foundation.

  2. Expert Member
    Akos | | #2

    Triple pane and vinyl casement is not the best idea. The IGU is very heavy and even with moderate sized openings, the window frame will warp over time. Unfortunately the manufactures don't tell you this and people end up with barely operable windows down the road.

    This normally would happen a couple of years down the road, so I'm not sure that is the case here, definitely not foundation shift. Bad window install is more likely.

  3. ohioandy | | #3

    Chuck, I've installed hundreds of windows, and I'm always amazed at the variation in final operability of identical windows. Installation is the major factor, as mentioned above. I wouldn't rule out framing movement, but I wouldn't suspect foundation settling without other obvious signs. There are so many deforming forces that can be applied as the flange is nailed, as sealant and insulation are pushed into the cracks, as trim is applied. Another major factor is the manufacturing tolerances that seem to always show in visible variations, regardless of whether it's cheap or high end. (A particularly troublesome unit was probably assembled on a Friday.) I always spend time "tuning" at the installation stage in an attempt to standardize the operation. Depending on how far along your are, maybe some tuning is still possible.

  4. walta100 | | #4

    If you suspect the foundation has moved look for cracks in the concrete.

    From your question it is not clear how complete your house is at this point.

    Are the windows still plumb at this time?


  5. user-6758514 | | #5

    Thanks to all who replied. As I think about it, of course deforming forces on the windows could as easily originate in the walls as in the foundation. (Walls are double stud walls, windows are mounted in the outer, load bearing wall.)

    Akos uses an acronym I don't know--IGU. Could someone please expand it?

    Thanks, CB

    1. ohioandy | | #6

      Insulated Glass Unit. Often you hear "thermopane" buts that's an early manufacturer's trademark. It's the glass sandwich, two or three panes with various coatings and gas fillers. Sometimes window manufacturers buy this from another company and build their window around it.

    2. Expert Member
      Deleted | | #7


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