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My uncle built a concrete bunker in the side of a hill over 50 years ago. The shelter seemed to be free of any leaks until just recently in which there is a steady drip in a few spots in the ceiling. With no rain for several months, the water must be coming from a spring in the hillside. Is there a sealer that could be applied to the concrete to eliminate the water from seeping through the concrete? If so, would the entire ceiling need to sealed or just in the area of the water stains?enter image description here

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    Feel free to try a concrete waterproofing product on the inside, but I'll be surprised if it works for any length of time before failing. Effective and reliable waterproofing is generally done from the outside, which in this case would appear to involve removing the hill on top of the bunker, temporarily. Alternatively, hang a gutter to direct the water to a drain. Of course, if you've had no rain for several months, perhaps finding a way to tap the spring would be useful, and have the side effect of reducing or eliminating this leak.
    – Ecnerwal
    Oct 11, 2017 at 21:26
  • @Ecnerwal this is old, but... if you convert that to an answer (which it is), it'll get at least one up vote so this'll stop popping to the top every couple of months.
    – FreeMan
    Aug 22, 2022 at 14:47

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Feel free to try a concrete waterproofing product on the inside, but I'll be surprised if it works for any length of time before failing.

Effective and reliable waterproofing is generally done from the outside, which in this case would appear to involve removing the hill on top of the bunker, temporarily.

Alternatively, hang a gutter to direct the water to a drain.

Of course, if you've had no rain for several months, perhaps finding a way to tap the spring would be useful, and have the side effect of reducing or eliminating this leak.

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  • And there we go! Thanks.
    – FreeMan
    Aug 23, 2022 at 12:17
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I don't know how well it works but there are companies that will drill holes through the concrete and then inject a waterproofing agent under high pressure. This is normally done for walls but I'd guess could work for a ceiling. It might even work better as for a ceiling as it won't sink down the wall outside.

If you search for "concrete waterproofing injection" you will find lots of companies selling the service and some reviews (good and bad). I've never done it. I looked into it a while back when I had a basement leak but I solved it another way.

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    Don’t drill through the rebar. When you say, “waterproofing agent”, what is that?
    – Lee Sam
    Mar 28, 2021 at 18:41
  • The method is called grout injection that utilizing pressure to force the grout into fine cracks. Can be effective, but could be expensive because it needs special equipment and knowledge of know-how.
    – r13
    Aug 27, 2021 at 0:09

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