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I have a portion of my deck that's a 4' square connecting stairs that go up and down from it. One of the corner posts (green post in the pic) has sunk between 1/2 and 1 inch and I'd like to raise it and pour a new deck piling to stabilize it. I don't think it's still sinking and has been stable in its current position for at least a few years. The wood seems all in good shape.

I'm a total newbie at this and am evaluating whether to even try this myself. I thought about using a jack to raise the corner, but I don't know where I can place the jack such that it won't interfere with my ability to dig the hole for the new concrete. When I tried to place it anywhere a foot or more from the post, it basically tries to lift the entire platform rather than the corner I'm concerned about. How could I effectively and safely raise the deck here while still leaving enough space to dig a hole around the offending post? Or is there another technique that might be better?

Approximate design below. Posts are 4x4 and platform is 4' x 4'.

To respond to @Ecnerwal's question about the screws versus nails attaching the framing to the post: lots and lots of nails, sunk deep into the wood.

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  • Those are cool floating steps! Is there a post supporting the stringer for the stairs? If so, it's highly likely that you could pull the post and replace it without any additional support. Heck, for a 4' x 4' platform, you could probably pull the one post even if there isn't a post supporting the stringers. Make sure you board it off while working to ensure nobody walks on it and I'd venture you'd be good to go. – FreeMan Oct 26 '20 at 22:10
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    If the post is screwed rather than nailed to the framing, consider unscrewing it, raising the framing, and re-screwing it, leaving the lower end that has stopped moving right where it is. If they were not so annoying to get out, you could do the same with nails, but they usually are miserable. – Ecnerwal Oct 26 '20 at 22:12
  • I like the idea of just raising the frame on the existing post, but there are a few screws, and lots and lots of nails attaching the framing to the post here. – Chris Farmer Oct 26 '20 at 22:22
  • @FreeMan, I agree that it's likely to be stable (or at least not dangerously unstable) without the post during a repair, but wouldn't replacing the post require the same jack issue in order to ensure that it's level? – Chris Farmer Oct 26 '20 at 22:27
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    Re: Nails - A "Sawzall" (the general tool, not necessarily the brand) will cut those right off. Re: Jacking it up - Once the deck is free of the post, drop a couple of concrete pavers right next to the post, put a hydraulic jack on the pavers, cut a 4x4 or 2x4 to just shy of the distance between jack & bottom of the deck, screw the wood to the joist temporarily, jack it up, screw it to the post, unscrew the temp support, done! – FreeMan Oct 26 '20 at 23:30
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I get the issue with the nails. I think you need to try to take them out.

I would start with a sledge hammer and try to tap one of the sides inward. When demo'ing a deck you are taking full swings to do the same thing but I would go really light. All you need is a slight gap. Once you get a tiny gap get a crow bar in their and try to get it popped out maybe to a 1/2" - I would not go further.

This only works if you can work it out without the rest of the deck moving and getting angles jacked up. So either you need to tap softer or just back out of this or try the other side and start over.

Once you get around a 1/2" (doesn't have to be that far) cut the nails with a reciprocating saw.

I would support this corner while you do this by either jack it up or throwing up something like a 2x6 which should be plenty with no load on deck. Now follow the same procedures for the other side and this side should be easier.

From there you need to raise the jack or 2x6 to level. Then drill a hole in each side for a lag bolt. Get your bolts in at level and then try to get one more hole on each side for another lag bolt.

Option 2... Dig post out really really good . Raise it up with jack and framing. Note that you must have this secure well to get the concrete raised (this could be easier if they didn't go very deep hence the sinking). Pour a couple more bags in or go down to the appropriate depth for your region. Let dry then take supports out.

Either of these options could be a 1 day deal. If you are dismantling a lot of the deck to get to post top (remember you have to saw those nails out) then I would try option 2 first. Digging this thing out in a muddy yard might take 30-40 mins and will give you an easy view of how hard it will be. This would be my choice if deck looked nice minus the tilt.

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  • Thanks for the suggestions. As for option 2, the post goes about 6 inches into the ground, and seems to rest directly on top of ~12" diameter concrete. The ground around it is easy enough to dig up. – Chris Farmer Oct 26 '20 at 23:19
  • Also, from a newbie perspective, can I ask what exactly you mean by "get the concrete raised"? – Chris Farmer Oct 26 '20 at 23:28
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    I would sawzall (with a demo blade -- 'wood and embedded nails') the post free from the rim/joists all day every day. Just pop the deck board that's on top of it (so you can cut from above and if cutting from below aren't banging at the underside with the tip of the blade) and start cutting. It's nice if you get a tiny crack to work the blade into, but you don't really even need to do that. The blade will cut a small kerf that you'll close up later when you reattach. – Aloysius Defenestrate Oct 27 '20 at 0:24
  • Either way will work. If the ground is pretty flat it is really easy to jack up the deck. Gets a little harder on slopes. If you don't have a way to jack the deck then number 1 is the clear option. As for digging - 12" diameter doesn't matter. You need to see how deep it goes. It would help to see pictures of your deck. – DMoore Oct 29 '20 at 18:45
  • I ended up jacking it up to secure it, getting the demo blade and taking out the nails, raising it and re-securing it. It’s nice and level now. Thanks so much for the suggestions. – Chris Farmer Oct 31 '20 at 20:17

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