Quote:
Originally Posted by widebody911
I did - why is that bad? I only used it for the top 2', so I could have the concrete above grade slightly.
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As someone else previously noted, you never do this for anything that needs to resist forces in a lateral direction. The reason is simple, you cannot get a tight fit between the sonotube and the hole, which means the portion of the pier that is encased in the sonotube is contributing nothing to the lateral resistance. This is probably your entire problem.
You need to redo these piers. Make the diameter large enough that you are bearing against undisturbed soils. You might have a little difficulty getting the old ones out of the ground without damaging they soil around the holes. Personally, I would probably rent a boom truck and pull them straight out vertically. If you want to use a short piece of sonotube above grade to form a round shape, that would be fine. I would also put rebar cages in the holes, I’ve never done a pier without steel in it.