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-   -   Concrete patio undermining question (http://www.houserepairtalk.com/f135/concrete-patio-undermining-question-13934/)

Hallhouse 05-06-2012 08:28 PM

Concrete patio undermining question
 
Hello everyone,
We just finished poring a new patio on Saturday. I tested the sprinklers before pouring and had no leaks. However that night after everything was cured enough to Start cleaning up I hooked up all of the sprinklers and placed them where they will go and fired them up to test. I noticed a little water on the deck in a strange place but didn't think much of it until I got working on the area close to that spot when I noticed a tiny bit of mud that appeared to have flowed out from under the new patio. I kicked that line up one more time for a sec and verified that we have water coming up right on a cold joint in the concrete.

The water ran under the deck for less than 1 minute total between three different tests. Probably less than 30 seconds. The pipe is a 1/2" sprinkler line with pretty high pressure. Both slabs have remesh in them. My contractor had agreed to deal with the sprinklers. I don't yet know what he'll suggest we do but I wanted to run this by you guys before we talk tomorrow.

One thought is to run a new pipe through a 3 inch conduit I had placed under the slab just in case. That would be fairly easy and wouldn't require several more days, even up to another week without the use of this beatiful new patio. Not to mention the cost to the contractor.

My concern is the extent of the damage that has already occurred. I know it's impossible to know, but I'm looking for oppinions or educated guesses on this. Do you think the damage would be slight enough in such a short time that I would be safe with asking him for a written guarantee that he would cover damage that occurs prematurely to the surrounding area for a number of years (Would 3, 5, or 10 years be appropriate) and having the contractor put in the new line? Or should I demand it be torn out and replaced? We put a lot of expense into the project to have it look good and last well.

If anyone has any questions please ask. Thanks for any advice you may have.

BridgeMan 05-06-2012 10:43 PM

You didn't say who installed the sprinkler lines. If they were done by the contractor, it sounds like he has a problem, and not you. It's too early to determine the extent of the damage to the underside of the concrete, but don't be surprised if it's significant. High pressure water and green concrete don't do well together.

Asking for a 10-year performance warranty would not be out of line. If it were mine, I'd take some Schmidt hammer readings after 14 days of cure time (he is correctly curing the concrete, right?). Low readings in the leak area (less than 2500 PSI) compared to other areas of the slabs would definitely warrant complete concrete removal and replacement.

Hallhouse 05-06-2012 10:50 PM

Thanks for the reply. The original lines were there for years. he did stub them out to the front of the patio with funny pipe.

I'm not sure what you mean by curing it correctly. We stayed off of it for 24 hours. He's supposed to come back on Monday and clean and seal it. It's stamped and colored which concerns me a bit, as far as trying to match the color.

BridgeMan 05-09-2012 03:20 PM

Curing concrete correctly means providing a means of preventing moisture loss in the mix. Hydration of water molecules by Portland cement particles is what gives concrete its strength, durability, etc.--contrary to what many people think, "drying" does not contribute to strength. Moisture loss can be prevented by covering with plastic, frequently wetting/misting the surface, or applying a liquid curing agent designed to minimize moisture evaporation. If your contractor simply walked away without doing any of the foregoing, the long-term quality of your patio will suffer for it.


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