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Thread: Question about a basement leak

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    DIY Junior Member riker1384's Avatar
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    Default Question about a basement leak

    We recently had a new deck put out back. They dug post-holes about 8 feet deep for it. While the holes were there, we had some rain and 2 of the holes collapsed, with dirt falling away from the house and exposing some of the foundation. They filled them in and completed the deck. I'm not sure exactly how well they filled them; it looks like there has been a little bit of subsidence, but it is small compared to the size that the holes were.

    Shortly after it was built, we had a leak in the basement wall during a rain. It's a small one, just enough to soak a couple bath towels during a big storm. It's along the back wall, but some distance away from where they were digging. Later, a smaller one appeared closer to where they were digging.

    We hadn't ever had the basement leak, for almost 30 years. Is it possible the post-holes had something to do with it? Now, one relevant thing is that the gutters in the back fell down a few years ago, so there aren't any there right now. I'm sure that's a contributing factor, but there were no actual leaks until just after they did this work.

    The other day during Hanna, we also had a tiny leak toward the front. There are gutters up there, in decent condition and clean. Incidentally, they also dug a few post-holes for some handrails out front, near where this third leak has started. (There were no problems with those holes collapsing.)

    We have a sump pit in the basement, but it was dry, at least after the first two leaks started. There is no sump pump in it, as we've never found water there.

    What is the likely cause of these leaks? (Besides the obvious that we need gutters in the back?) Also, what's the best thing for patching these leaks?

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    Moderator & Master Plumber hj's Avatar
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    Default leak

    NOTHING they did would have caused the wall to leak, but changing the grade of the ground could have allowed water to flow back to the foundation and then show up as a leak when it had not happened before. Your description of the occurance is somewhat puzzling. Why were the holes 8' deep, and when they collapsed, unless they were very large diameter, why did so much earth move?

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    DIY Junior Member riker1384's Avatar
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    Quote Originally Posted by hj View Post
    NOTHING they did would have caused the wall to leak, but changing the grade of the ground could have allowed water to flow back to the foundation and then show up as a leak when it had not happened before. Your description of the occurance is somewhat puzzling. Why were the holes 8' deep, and when they collapsed, unless they were very large diameter, why did so much earth move?
    It's a good-sized deck. They were required by the building code to dig the post-holes down to the same depth as the bottom of the foundation of the house. They put a little bit of concrete at the bottom of each hole, placed a post on top of that after it set and then filled the holes with dirt (And maybe a little more concrete at the bottom). Each hole was maybe 18 inches square, I think.

    When the 2 holes collapsed, the dirt that fell down came from the side closer to the house. So, if you looked down into it you could see the side of the foundation. The holes were dug a foot or two away from the house, before they collapsed.

    There weren't any major changes in the grading around the house. There were some subtle changes under the deck just because of digging the holes and also having some extra dirt that came out of them, but that's it.
    Last edited by riker1384; 09-10-2008 at 07:05 AM.

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    Plumber Cass's Avatar
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    I would get the gutters fixed then see what happens.

    It may be that the earth needs to compact better than it is now, if it has sunk down you need to fill it, loose earth may allow water to percolate down to areas that it may not have reached in the past with enough flow to leak through to the wall.
    Last edited by Cass; 09-10-2008 at 08:34 AM.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Take a level and make sure that the soil slopes away from the house as HJ said...in the process of excavation, it may now be either level or slope towards the house.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Senior Robin Hood Guy Ian Gills's Avatar
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    In my great experience of basement leaks in my house, 90 percent of the time it is gutter-related.

    The one at the back needs to be fixed. And I swear my gutter guards cause me problems in heavy rain, so if you have these there might also be a problem there.

    The other 10 percent I have found to be:

    1) leaking windows or doors upstairs - watch for a leak appearing in the basement directly below a window or an exterior doorframe upstairs. You'd be surprised how much water can get in through the tiniest gap that has been left unsealed. I use caulk to seal any gaps.

    2) small cracks in the masonary above grade that allow water to seep down below grade into the basement. I had one on my front door step of all places that appeared as water coming from the bottom of the wall in the basement directly beneath it. I used hydraulic cement in this case.

    Torrential rain is the best way to test for leaks. Some problems will not show up without it. Since it only rains really hard a few times a year where I live (in DC), some leaks can be hard to spot.
    Last edited by Ian Gills; 09-10-2008 at 11:20 AM.

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    In the Trades AZ Contractor's Avatar
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    Three things I can think of but they were all already mentioned.

    1- Soil is more permeable when its not compacted. Water can be pooling up against the foundation where the cave in was and following the path of the foundation until it finds a crack.

    2- Check for proper grading.

    3- Put in a new gutter.

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    Plumber jimbo's Avatar
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    DId they disturb the ashphaltic barrier coating on the foundation wall?
    Did they damage a french drain system around the foundation?

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    DIY Junior Member riker1384's Avatar
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    Quote Originally Posted by jimbo View Post
    DId they disturb the ashphaltic barrier coating on the foundation wall?
    Did they damage a french drain system around the foundation?
    I don't know that there was any sort of coating on the foundation wall. As far as I remember, all I saw was bare concrete, but I might be mistaken.

    I don't know anything about a french drain. When they dug, all I saw down in the holes was clay and some rocks.

    Anyway, we're having new gutters installed. We're trying those Leafguard covered ones. I'm a little bit iffy about those because they're expensive, and I wanted to get a quote on regular gutters and then figure out the total cost of ownership including cleanings. I'm not the owner though, and the contract is already signed. Hopefully that will solve it.

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