Add vertical rebar to deck footing after drying?


Old 07-24-19, 12:06 AM
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Add vertical rebar to deck footing after drying?

I'm in the process of building a deck. Originally, for several reasons, my footing and post approach was to dig down below the frost line, pour about 8" of concrete, and then put my treated posts on the concrete and then backfill with dirt or gravel. According the Intl Building Codes, this is an acceptable approach:

After thinking about this more and researching it more, I'm worried about the longevity of this approach even with treated wood. So I have decided to shift gears to do something else. I'm now wanting to do this instead:

Now, the problem is that I've already dug and poured my footings. I'm talking about ONLY the large flat 8" footing in the first diagram. Not the pier as in the 2nd diagram. So I'm wondering, is it okay to pour a pier on top of an already dried footing? It is possible this could create some sort of unintended air gap between the two? Obviously if I had taken this approach from the beginning I would have poured it all at once but its too late for that.

Also, in order to help improve the connection between the dry footings and the new piers, I was thinking about drilling into the footings and putting in a few pieces of rebar sticking out vertically. Then I would pour my pier (using a Sonotube or something) centered on the rebar. So that would hopefully help tie them together better. My question here, is it okay to drill out and put in rebar into the dry footing? Do I epoxy it in there or what? Obviously it would have been best to put in the rebar at the same time as the footing but again, too late.

Can anyone give me some guidance here? Thank you in advance.
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Old 07-24-19, 01:59 AM
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Although I would do differently today your approach is basically what I did for my deck although the depth of the pier was about a foot below grade.

For structural strength it's never good to have a cold joint in concrete and the rebar will not fully resolve.
Old 07-24-19, 06:08 AM
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I think your good, like having a stone on stone foundation some have lasted many years. The rebar would be better for side movement depending on how you sealed it in. Good luck.
Old 07-24-19, 07:39 AM
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If you really want your rebar pins to hold in the old/existing footer I would epoxy them in. There are special epoxies intended for anchoring bolts in concrete. The added uplift protection wouldn't hurt if you are in a coastal/high wind area.
Old 07-24-19, 08:24 AM
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I'm in Colorado so not much of an issue with wind here. Would the rebar only really be adding uplift protection?

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