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Background

Part of my tri-level house is supported by a crawlspace. The crawlspace has 3 rows of six 4x6 posts sitting on concrete piers. A couple of weeks ago I noticed that the bottom of three of the posts were not touching their respective concrete piers; they were floating a fraction of an inch above the the pier.

I hired a structural engineer to come look at the issue. The sinking piers are likely due to water + soil issues. (We did install a sump pump after moving in a few months ago because there were several inches of water down there after heavy rains.)

Longer term, I'm hoping the sump pump can help stop the settling of the piers. Perhaps I'll add a drainage system around the house too in the future.

My goal

I want to fix/replace these posts so that they are again supporting the floor girders. My plan is to jack up the girder 1/8th of an inch, remove the old post, cut & replace it with new 4x6 PT post that is the proper length, then remove the jack.

Question

I am considering just placing a piece of metal in between the bottom of the new post and the pier (so that contact + weight keeps the metal in place) but not physically attaching the post/metal/pier with screws or nails. Do I have to physically attach the bottom of the new posts to the concrete pier? My concern is that if there is continued settling and the post is physically attached to the pier that (1) I will not notice that there is settling because the gaps won't appear underneath the posts, and (2) the weight of the sinking concrete pier could pull down the girder due to its weight, more so than it would if the post were just 'free.'

Even if there is continued settling, is it best to make sure the post is attached to the pier rather than just sitting on it?

For what it's worth, none of the other posts have any base bracket of any kind. Most have some 6 mil and/or roofing shingles sandwiched between the pier and post.

  • Since you've already engaged a structural engineer who will have a greater bank of knowledge on what to expect for your region/building type, why not ask their recommendation? – Chris Jul 11 '16 at 20:05
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To meet modern best practice you'd want both ends of any post anchored. Obviously your particular home isn't going to collapse if a post was to fall out (and it's unlikely it could anyway with that small of a gap).

To slightly derail the conversation, I'd seriously consider permanent adjustable floor jacks for your purposes. Why not build some future-proofing into your solution (assuming you aren't opting to dig proper footings)? They aren't terribly expensive (for the few you want to fix), and they'll allow you to add height down the road as needed.

  • +1 Further, the gap indicates that there is no settling! – bib Jul 11 '16 at 22:08
  • My concern about using adjustable floor jacks is that the ones I've seen aren't designed for permanent use. If we ever sold our house I'd probably have to make them more permanent for code, yes? Also, good point about the gap indicating a lack of outer foundation settling. I suppose I'm trying to correct the pier settling. – BMS Jul 12 '16 at 18:40
  • There are houses all over the upper midwest (and I assume elsewhere) that have steel, adjustable posts in their unfinished basements. They're also used for finished basements. My home has them embedded in finished walls. Check your local codes, but I'd have no concerns using them. – isherwood Jul 12 '16 at 19:27

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