Background: when I moved in in 2018 I had the sewer line replaced. This necessitated cutting a section of the basement floor, which was then filled with concrete:

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The contractor left unfilled a small slit from where they sawed the original concrete:

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Last week we had a huge, historically-unusual rainfall onto already-saturated ground. There was widespread flooding in the area. In my basement, water flowed up through this slit (and also trickled through a crack between their patch and the original concrete). It flowed steadily across the floor and down the floor drain. After about 12 hours of this, the water stopped flowing up.

What caused this and how should I remedy it? I believe my house has footing drains connected to the sanitary sewer, which I understood to be good protection. Do those drains not protect the basement from water table rise from below?

1 Answer 1


I suspect the concrete replacement did not contain the correct amount of cement (the yellowish color looks odd) and the job wasn't done the correct way. The extensive/heavy storm has caused the groundwater to raise, and the pressure forced the water to seep through the shrinkage cracks between the old and new concrete contact surface, and the through-depth slit left by saw cutting.

This is the way I expected:

  1. Saw cut the concrete to the depth approximately equal to 1/3 of slab thickness.

  2. Chip out the concrete and let the surface remains irregular in shape for better bonding with the fresh concrete.

  3. Insert steel dowel at a spacing not greater than 18".

  4. Thoroughly clean and moisten the rough surface.

  5. Install 1/4" - 1/2" thick removable felt on the smooth saw cut surface and place the concrete.

  6. After curing for at least 21 days, remove the felt, and grout the gap with a water-resistant sealant. Note you can remove the felt once the concrete has hardened (approx. 3-7 days). Be careful not to damage the concrete and place plywood board for walking around before finishing.

At this time, I don't think you have much choice but to redo the cutting and capping on an area slightly larger than the original.

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