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My deck has 6"x6" wooden support posts sitting atop 12" diameter concrete footings. The tops of the concrete footings are about 16" above grade. When I inspected a little below grade, I discovered the 12" diameter footings end just 2-3 inches below grade, but they seem to be poured on top of 6" diameter concrete footings. The 6" footings completely underground, and have an unknown depth. The deck over the posts shows no sign of settling/heaving however, and the deck appears to be at least 10 years old.

The wooden posts appear to have no attachment to the 12" pillars: one of the posts has shifted to the edge of the 12" footing. I would like to attach the posts to the footing using a rebar post holder by drilling a hole in the center of the footing, and using epoxy or some adhesive for the holder.

My concern is that the footing may crack during drilling. Is this much of a risk for a concrete footing this size?

  • wood breathes. is it shifted as much in the winter as in the summer? if not, then you might be worse off locking it down tight; that tension will eventually find a release, probably warping the surface – dandavis Jul 7 '17 at 0:43
  • Dou you even KNOW that it moved? Could be it was just built sloppy and has set right there for the past 10 years or so - you look and see it off-center, and assume it's moved - but if you didn't look and see it centered at some previous time, there's nothing to support that assumption. – Ecnerwal Dec 6 '17 at 3:41
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Drilling with a rotary hammer at a high speed with low force should not crack the footing, assuming it's in good condition.

I wonder why the one post has moved, though, and the others haven't. Is the structure that loose? You might just repair and bolster the framing and not worry about anchoring the post at the footing.

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