Concrete Foundations Must Be Strong
DEAR TIM: My husband and I hired a contractor to build a 25 by 25 foot addition. This addition has a poured concrete foundation. Because access to the jobsite is very difficult, we had to use a concrete pump to place the concrete in the forms. Immediately after the pour, the concrete-pump operator didn't think things were quite right and implied it was the concrete. During the pour, he needed to clear out the pump several times. As he was packing up his equipment to leave, he asked us if the concrete seemed to be getting hard. From what we could see, it appeared fine.
At the time we didn't realize it, but his was our first red flag. Several days later, my husband found concrete in a pile that was cleared out from the pump and he was able to crumble it. Then he had to drill a hole for a drain pipe and he thought the hole was too easy to drill.
We tested the concrete and the results showed the concrete had an early strength of 1,100 pounds per square inch (psi) and few weeks later it tested to 1,600 psi. Our understanding was that it should have been quite a bit higher at this cure point. For the record, we ordered a 3,000 psi mix.
Our structural engineer recommended we get a more thorough test to find out exactly what happened. We did do this rather expensive test and discovered there are many variables that can make the concrete test so poorly.
The structural engineer indicated that we need to take out the foundation to take care of this problem, but then he also says that we could probably live with the compromised concrete because our addition probably won't collapse. Neither of these scenarios really helps out because of the amount of money involved. We have already spent quite a bit of money on testing, structural engineer advice and we don't even have the slab in!
We used insulated concrete forms (ICF) and it seems that might be a problem. I don't think our structural engineer is that familiar with them. All the same, we would love to know if you have any alternative solutions to dealing with this compromised foundation. Just building on it the way it is with the concern of leaks, cracks, settling etc. doesn't seem to be the smartest move. Katie Nunez, Newtown, CT
DEAR KATIE: One of the things that amazes me about your story is the noticeable absence of your contractor. Where is he in this debacle? Unless you do things differently in Connecticut, I would think he has an obligation to make sure the job is constructed correctly.
But let's start with the facts. The concrete test results tell me everything I need to know. Assuming you used standard concrete, if there really is such a thing, seven days after the pour the strength should have been 2,250 psi. You poured the concrete in nearly ideal conditions since you used ICF forms. These wonderful foam products help retain the heat created by the chemical reaction that happens as the concrete hardens and cures. This is an important thing to keep in mind since the work was happening in cool or cold weather.
You have several problems as I see things. If your state is like mine (Ohio), you have a property disclosure law where you are obligated to reveal known defects to future buyers. Can you see the nightmare this might create five, ten or fifteen years from now? If you think it is expensive to install a new foundation now, just wait fifteen years to see what it will cost with a finished room addition on top of it.
The other problem is the basic one of having a substandard foundation. In my opinion, this is simply unacceptable. A strong poured concrete foundation is the key to a room addition that will stand the test of time.
The solution to this mess seems straightforward to me. I would immediately stop all work. Then I would contact the ready-mix concrete supplier with a copy of your delivery ticket proving you ordered a 3,000 psi mix. This ticket will also have another critical piece of data; it will show if any water was added to the concrete mix once it arrived at the jobsite. If a significant amount of water was added at the jobsite, we may have discovered the smoking gun.
For sake of discussion, let's assume the problem started with a bad batch of concrete at the ready-mix plant. There is a strong possibility they have insurance that will cover the loss. If the fault lies with another person or persons, contact their insurance agent(s).
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