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I'm building an attached deck and have already buried precast piers in the ground. Unfortunately, I had to dig so deep that the tops of the piers are below finished ground level. I'd rather not bury the 6x6 posts. The tops of the piers are 8"x8". Should I use sonotubes and pour concrete on top of the piers (assuming I can jury rig round sonotubes on top of a square pier top) to bring the piers above ground level? How about putting a post sleeve around the post to keep it away from the soil? I know metal and today's PT lumber aren't friendly with each other, so could I use plastic sleeves?

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  • How far below ground are the top of the piers? If it's not too deep, you could set post blocks (those pyramid looking concrete blocks with post anchors on the top) to raise it a bit (assuming the top of the poured piers are nice and flat.)
    – DA01
    Aug 18, 2014 at 23:26
  • If the piers aren't very far below finish grade, you could also surround the posts with 1-1/2" crushed rock to grade. It's nasty stuff to shovel, but it drains marvelously. If you sleeve the post, the sleeve will just catch & trap water. Aug 19, 2014 at 2:46

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Without seeing the plans and what kind of precast piers you have - I would say that I'd pour more concrete, with some rebar drilled and epoxied into the precast piers and the new concrete poured over to join them both.

Then set stand-off post bases into the new concrete for the PT posts.

post base

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Pour your concrete first and set the preformed pier on of the concrete to get the post bottom about 4 inches above grade. No sonotube needed.

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  • Too late. Piers are already in the ground. Aug 2, 2014 at 11:20
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Pressure treated lumber is rated for ground contact. A common way of creating footers that I have seen is to pour concrete down in the hole, but below grade. Then just put the post on top of that and fill with dirt. I personally wouldn't do that, but I have heard of it being done. I would probably pour concrete in a tub on top of the footers and bring them up out of the ground 6-8 inches. The gravel isn't a bad idea.

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