New Concrete Piers Repair

[schmeling]

:oops:
I just poured 8 concrete piers this week for a deck. The piers go down 48 inches. They are about 9-12 inches in diameter at the bottom. The top 12 inches are 8 in diameter with an 8 inch J-bolt at the top.

I waited a two days to bolt the post anchors to the piers and attached the posts. The next day the piers broke away just below the J-bolts (about 7 inches down). I think that I did not wait long enough for the piers to cure as they appeared "wet" where they broke.

My one neighbor, who is a builder thinks I need to break up the piers and remove them!

However, a friend said I should just get a larger diameter (10-12 inch) sono tube, drop it over the existing pier and put a new top on the original pier. When I expressed concern over the strength of this approach he said I could reinforce them by putting bolts half way into the original pier.

The main purpose of the pier is to provide a surface for vertical compression support, not tension, so it seems like this might work. Could anyone help me on this?

[Rich]

All the piers broke? Were they poured up to that level and then a final pour over that?

[schmeling]

So far 3 of the eight have broken. These are the first three that I started working with.

I was mixing cement by hand and pouring one bag at a time. I was looking at it this morning. On one of the three broken piers looks like it broke at a point where I changed bags. On that particular pier, I ran out of cement and had to run to the store to get more.

The other two piers just look like they broke a little below the J-bolt.

[Rich]

Huh..
I would probably chip down below where the end of the j-bolt would be (maybe 6-8") drill and epoxy 2 pieces of #4 rebar into the existing concrete maybe 12" and repour the tops. The rebar will give it a little better bending moment right at the union of old and new and also help keep the pieces together better.
If you just pour right on top of the old one (where the j-bolt is) it will most likely break there again. I would try and go below that. Sticking a sonotube over the top won't help you much.. it'll act more like a thimble which come off pretty easy too. And most likely between the old concrete and the new (thin section) you would get more breaks anyway.

[mjpliv]

It sounds like your pier separated on a cold joint. Running out of product and having to run to the store would probably do it.

Rich is right. Chip down (leave the surface as rough as possible), drill and epoxy in a few steel dowels. A little bonding agent wouldn't hurt either.

[schmeling]

Thanks for your help and feedback.

I spoke to a construction engineer who has done a lot of work with concrete. Thought you might like to hear his recomendation. It is very similar to yours.

He said I should drill into the original concrete about 1ft and drop in a long piece of threaded steel rod. This rod will serve as a concrete reinforcement, and will also be the bolt for the post. This way the post will be connected to both the original and new concrete.

I'm using a 2ft-1/2 inch diameter rod, which I will trim to height. This should be attached to the original concrete with epoxy, like you both recommended.

Then drop a 12" sono tube over this and fill.

Thanks again.

[Rich]

Geesh.. another engineer that thinks he knows what he's talking about.. :rolling: haha.. just kidding.

[Ben Thayer]

My local Home Dumbo rents mixers for $60/4hrs a real back saver ;)

[skipmarr]

We had a deck built out of treated lumber and Trex. The post were put into the footing and then concrrete was poured around them to fill the footings. I am concerned thatt the wood will rot with the constant contact with the ground. Dan anyone suggest a way to correc this short of jack hammering out each pier, pouring the pier, then putting the posts on brackets - the way it probably should have been done.

Thanks for any advice or referral.

[Tom R]

Let's put it this way, I've used this same method on decks I've done 15 years ago, and they're still as strong as the day one. And I still do it this way. Makes for a much stronger deck/rail system because of the 'continuous' posts. I don't do it because it's easier (it's not), I do it because it's stronger. And although 9 out of 10 people will say it's the wrong way to do it, and it's not 'allowed', it's been 'detailed' on my deck drawings, and always gets approved (at least in my town and several surrounding towns). If you're really worried about it, coat the grade-area of the posts with creosote (or similar).

[mjpliv]

My only concern would be from any lateral "shifting" of the concrete from frost. This can be a real problem locally but may not be an issue in more temperate climates.

Attaching the wood post with a saddle bracket gives you the opprortunity to "adust" the connection later on.

[skipmarr]

Tom,

So what you are saying is that in NJ it is not a problem. I am in Missouri.

The footings here are required by law to be min. 30" though I think they went down 3'+. The posts are 6x6 treated, and the concrete is about 4" below the grade. If I understan you, you suggest I coat or insulate the exposed posts from the soil? What about the post that is in the concrete in the ground? Will this not eventually rot due to the moisture in the cement?

I am askeing what may seem a lot of silly questions, but I ma just a homeowner and not a builder/contractor. I really appreciate your comments and advice.

Thanks.

[Tom R]

I do it the same way, stopping the concrete 4-6" below grade, then fill to grade with soil. I also put 2" of gravel at the bottom of the hole, before installing the post, or the concrete. If you were to ever have a problem, though it would be 'years and years' down the road, it would be at the soil/air intersection, mainly because the soil-section is taking on moisture, whereas the 'air'-section is taking on sun. That's why you would creosote-coat from the concrete-section of the post to about 3 or 4" above grade (maybe 2" in Missouri). To make it look 'neat and professional', first put masking tape square around the 'height' line, then creosote, then remove the tape. As far as the part of the post in the concrete taking on moisture - - not a problem - - Did you know that when they originally 'tested' treated wood they buried a 4 X 4 in a swamp in Louisiana - - pulled it out 32 - - yes, 32 years later - - Bingo - - nothing wrong with it! P.S. Ask all the questions you want, that's what this site is for.

[Rich]

Careful on that test of treated wood. They later found out the reason why it lasted that long - no air. They've pulled wood that was sunk underwater (saltwater, swamp, and clear) many years ago and it's just fine also - no treat at all and also no air. Not saying the treat didn't help but there are many differences in real world and that test.
Like you said - the problem area is where the encased (no air) post meets above grade (air).

[Rich]

I should also say - not sure if my rendition is in response to that exact test but a very similar one.

[Tom R]

You're right, Rich. I referred to that test in answering his question about the part of the wood 'encased' in concrete.

[Rich]

:) oh
I should read better eh?