I have a hole in the concrete floor of my basement. It's about the size of a quarter and is deeper than a chopstick (I didn't try putting anything deeper in there). I'm including a picture below.

I've lived in this house for a few years now. According to the realtor (we bought an estate property) there was a major project to replace some sewer lines due to a large tree growing outside near the house. This might not be related to the patched concrete that @Ecnerwal mentions, but I figured I would add this info in case it's relevant.

Question 1: What the heck could be causing that hole?

Question 2: Is this something I should try fixing or have someone come take a look at? I'm generally game for fixing it myself, but wanted to see if you think there are bigger issues that could be causing this.

Question 2a: Any recommendations for what I should do to get started?

enter image description here

Here's a picture of a wider area: enter image description here

  • Thanks for including a photo! Looking at this, it would be helpful to also have a photo of the general area, in addition to the detailed one you already posted. Could you edit your question and add such a photo? Maybe there's something in the surrounding area that gives us a clue. Feb 9, 2022 at 2:20
  • 2
    Clearly the area above/right of the hole is a newer patch, with the hole along the boundary with the older concrete left/below.
    – Ecnerwal
    Feb 9, 2022 at 2:56
  • 1
    Concrete termites.
    – FreeMan
    Feb 9, 2022 at 14:26
  • @PhilippNagel here's a picture of a wider area. I'll try to see if I can edit my question to add the picture there as well. Feb 9, 2022 at 15:22
  • 1
    Those don't chirp, they are the sad cousins who look ugly, can't sing, and never go outside.
    – jay613
    Feb 9, 2022 at 22:39

2 Answers 2


If it were mine, I'd mix up some hydraulic cement a bit on the fluid side, pour that in until it was about an inch below the surface (hopefully not requiring huge amounts to fill a huge void below) and then mix some up stiff to plug the top inch of the hole after the lower part had set.

Or get out the sledgehammer to find out if it's buried treasure or something less delightful under the patched area, then repatch with regular concrete mix. Probably related to the sewer work, per your update. A more pedestrian less delightful best left alone.


I had a similar size hole found when putting ceramic tile down. I just put tile over the hole. The house was several years old . I knew the foundation had been poured in winter ( IL). I believe there were chunks of ice and snow on the ground when they poured the floor and there was an ice chunk that was just covered by the concrete, by the time it melted, the concrete had set up enough to bridge the gap. When I was putting on the ceramic tile I pushed through the thin spot. The hole was a couple inches deep and about the same width.

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