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We have a below-grade basement with a walkout door. In between the concrete stairs and the foundation floor there is a tiny gap (see 1st picture below). During extended heavy rain, ground water would ooze out of the small hole at the left corner (2nd picture).

We have a working sump pump and the outside soil is graded properly so there is no standing water on the ground. This happens only when it rains heavily and continuously, so my assumption is that the water table is brought to the level of the sump pit while it rains continuously and the water flow rate in soil is just not fast enough to drain completely to the sump pit.

What's the best solution in this case? I'm thinking of using 1) Hydraulic cement like this; 2) Polyurethane sealant; or 3) epoxy or polyurethane injection-type concrete repair kit. In (3), my worry is how to securely place the injection port on the angled surface.

Overview Detailed left corner

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  • you have no landing at the bottom of the stairs? code here has the door threshold 4" above the stair landing. if that is your door trim butting up to the bottom riser - that seems crazy. Jul 24, 2023 at 0:25
  • @FreshCodemonger Older buildings may not meet code in that regard. My basement just has poured concrete straight through the opening.
    – keshlam
    Jul 24, 2023 at 0:47
  • @FreshCodemonger Yes, that is basically my door trim up against the bottom riser. In the first picture, the two sides with weatherstripping are the door trims.
    – P. B.
    Jul 24, 2023 at 3:03

1 Answer 1

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How sure are you that this is exactly, and only, the place where water is coming in? I patched some weeping cracks in my stair enclosure only to find that most of the leakage is coming through the bulkhead doors above; someone "helpfully" fitted them with deadbolts and the holes they bored to mount those keep water above the door from being properly directed to the sides.

Also, note that the enclosure may have been cast separately from the stairs -- the stairs may be a precast unit dropped in, as my wooden bulkhead-door stairs were -- so the crack you are looking at may not actually be where the water is coming in, and closing it up may just mean the water backs up around the steps and flows from higher up.

But presuming this is indeed the entry point... If it's a wide enough crack to stuff hydraulic cement into, that's the most basic solution. Wide cracks are also harder to fill with the injection polyurethane, at least at reasonable cost; hydraulic cement is cheap. And this isn't a structural issue, so epoxy injection would strike me as overkill, as well as not being cheap. While using ordinary spray foam is tempting, and might work briefly, I'm not sure

I've used the poly injection systems on thin cracks. The good news is that if you take your time and are careful and slightly lucky, they can work well. The bad news is that "if". The poly has to be injected into the crack with exactly the right amount of pressure and a LOT of patience; if you try to push it too fast the injection tube pops off and makes a mess, and "too fast" is still pretty darned slow since you're trying to push a thick fluid into a small space and persuade it to flow until that space is filled. It's frustrating enough that, if I do it again, I'm going to be seriously tempted to pay the extra money for their modified caulking gun which maintains the correct flow rate without needing a death-grip on the trigger, and doesn't allow you to exceed that rate.

Don't know if that helps, but not being able to examine it directly, this is the best I can do.

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  • Thanks for sharing your experience! The gap is about 1/16 -- 1/8 inch. I'm pretty sure right now water is coming in from the circled corner in my second picture. I can see a stream of water flowing out there. There is also a rod of caulk the previous owner must have filled in the hole. And that rod is really deep. I can only clean out the top portion. Not sure if the residues would interfere with the repair. I appreciate your tips on using the injection repair kits!
    – P. B.
    Jul 24, 2023 at 3:13
  • I don't know how the stairs were constructed. It's possible that once this spot is closed, water may come in elsewhere. However, it is currently a pretty localized stream of water.
    – P. B.
    Jul 24, 2023 at 3:15

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