A.Carl Hagstrom responds: There are plenty of ways to detail such a joint. I recommend using a backer rod and urethane caulk. If possible, it’s best to apply this after the concrete has had about six months to cure and shrink back. But this is just a band-aid, not a lasting solution to the problem. You have to deal with draining the water first. Then you can worry about sealing the joint to keep out radon gas, if necessary.

Here in northeastern Pennsylvania we have high seasonal water tables, so on all foundations we pour, we have to use an interior perimeter drain to deal with the water. Most builders think in terms of an exterior drain. But if you have a high water table, the water will rise inside the foundation. Unless you have an interior drain, the footings...

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