After a couple of rod holes started leaking behind a finished basement wall, we decided on a proactive campaign of basement waterproofing. We found several more rod holes either leaking or about to leak, but the most perplexing find was a sheet of bubble insulation glued and pinned to the concrete basement wall. It was clear that there was a problem behind there because the texture on the basement wall next to it was showing indications of water, so I ripped it down and found a cemented area that was visibly wet. The cement stops a little below the top of the basement wall, and there's a decent-sized crack visible there. Since I exposed the area a couple of months ago, the cement has remained damp to the touch.

I have two questions:

  1. What's going on? I'm assuming this was a crack in the basement wall that has been repaired, but how can the water be leaking through the cement?
  2. What should I do to fix it?

Photos: Front-on Looking up Under the carpet

Clarification: I need to fix this from the inside. Fixing it from the outside is not an option (due to money and practicality). Presumably I first need to remove the existing "fix". How should I do that? Then what's the best way to fix it "properly"? Any idea what's going on under the carpet?

Update: The plastic was part of a waterproofing solution by Foundation Systems of Michigan. It was leaking so I ripped the plastic off the wall. It turns out that it would have been under warranty if I hadn't touched it (not that there were any labels telling me it was under warranty or who to call; I called them for a quote on the repair and they happened to have done it in the first place). Now they want $1000 to fix it, but even if they were going to do it for free I don't trust them to fix it correctly after they've already gotten it wrong once. I can fix it myself better and cheaper.

What's going on under the carpet is that's where they've refilled with concrete after digging out the basement floor. Their "solution" is supposed to channel the water leaking in the crack down and out under the basement floor where it should get picked up by the interior drain tiles, dumped into the sump and pumped out. I don't like this "solution": I would think that having water leaking through the wall is eventually going to cause more problems (freeze-thaw cycles, particulates getting into the drain tiles), so I would rather keep the water out in the first place instead of redirecting it.

2 Answers 2


Water will always win if you "fix" these from the inside.

The correct, effective, and unfortunately expensive fix is to excavate outside and drain the water below wall level outside, then seal and drain the exterior of the wall to the exterior drain.

You may choose to chisel out this mess and try fixing from the inside again, but it will almost certainly fail again. The other inside approach is to "capture" the leak and lead it to a sump.

If tilting at the windmill, this image from "www.oldhouseweb.com" illustrates the correct shape for chiseling or diamond-blade cutting out the crack before attempting to re-fill it. At the bottom of their page they note that their information came from Michagan State University Extension publication E2109, and the image would appear to also have come from that publication originally.

enter image description here

  • I agree, but it's worth trying a product like UGL Drylok before taking that big, expensive step.
    – isherwood
    Aug 1, 2016 at 17:12
  • I'm gonna hafta "tilt at the windmill" because it's under the patio outside and I don't have the $$$. Is it worth trying to chisel the cement away and then either using the correct-shape with some hydraulic cement, or some epoxy injection; and then maybe Drylok over the top? May not last forever, but maybe will last "long enough"?
    – Paul Price
    Aug 1, 2016 at 19:10
  • Yes, that's the way to go at it. Sancho, my masonry chisel! ...he said, Quixotically
    – Ecnerwal
    Aug 1, 2016 at 19:19
  • I would add that after you finish your repairs remove the plastic from the wall if you reassemble it. Plastic just traps moisture and promotes mold growth. The wall needs to breathe and dry to the inside since it can't dry to the outside. Good luck!
    – ArchonOSX
    Aug 1, 2016 at 19:33
  • Also do whatever you can to get surface water away from the area - the patio should slope away from the house, gutters (add if not there, check function if there, extend downspouts if needed..) ground slope in general.
    – Ecnerwal
    Aug 1, 2016 at 19:39

Sorry, I just don't buy the line that "the correct ... fix is to excavate outside". I'm sure that's probably the most effective solution, but that doesn't mean it's the correct solution because it's not satisfying the other boundary conditions (i.e., manpower and cost constraints). I doubt whether those who suggest fixing things on the outside actually do that themselves when they find leaks in their basement walls. Surely there's a cost-effective solution that will allow me to fix it from the inside!

So, I tilted at the windmill, and tilted hard. I started by chiseling away some of the concrete that had been used to previously repair the crack. In hindsight, that was a mistake, but it confirmed for me that the crack was very thin and that I didn't want to attempt to solve the problem with cement --- that's already been tried unsuccessfully, and I didn't want to have to rely on my ability to form the correct shape with a chisel. I decided to go for polyurethane injection. However, because the crack is very thin, previously repaired and actively leaking, this required a different approach than the usual injection through epoxy paste over the top. I found the Acta-Leak Crack Repair Kit from Applied Technologies.

The kit costs $200 (I tried to buy it on Amazon, but they wanted an extra $20 for shipping; that policy seems to have changed and they now appear to offer free shipping), and there's a video with instructions. The kit included:

  • Gloves (cheap, tear easily; get your own)
  • Plastic bag/drop-cloth (too thin and small; get your own)
  • Protective goggles
  • Water squirt bottle
  • Grease gun (decent quality, but treat it as disposable; you can get replacements for $15)
  • 20 packers/injection nipples (3/8 inch)
  • Polyurethane goop to inject

You'll also need:

  • Hammer drill (can get one for $50 from Lowes or Home Depot)
  • 3/8 inch x 12 inch masonry bit ($15 from Lowes)
  • 3/8 inch socket and ratchet (may want a deep socket to get over the nipple)
  • Plastic drop cloth
  • Can of compressed air is helpful

The idea is to drill in behind the crack (not into the face of the crack!) and inject the polyurethane goop, which will foam on contact with water, force its way through the crack and harden over the course of hours, sealing the crack.

  1. Mark locations about 5 inches to the side of the crack, alternating sides as you go up the crack with each about 8 inches apart vertically.
  2. Set your hammer drill to go about 7.5 inches in (I used a bit of tape on the drill bit).
  3. Drill at a 45 degree angle to get in behind the crack (start perpendicular to the wall, then kick over to 45 degrees once you've got it started).
  4. Blow some compressed air down a straw into the hole to get the dust out.
  5. Flush the hole with water from the squirt bottle. Besides clearing out some dust, this also provides some water to activate the polyurethane foam.
  6. Insert the packers and tighten with the socket+ratchet. I had some of the foam leak out the packers which makes me think I didn't tighten them enough (I was worried about over-tightening; maybe that's something you shouldn't worry about).
  7. Do the above for all the holes before proceeding (because the goop is going to destroy the grease gun before you can inject into every hole if you don't). Now don your gloves.
  8. Fill the grease gun with the goop, close it up and prime it (unscrew the top, pull the plunger back, pour goop into the canister, screw the top back on, hit the plunger release button, pump until the goop starts coming out the spout, you may have to hit the plunger release button a few times as you pump so that the goop is pressured). My kit included some little plastic pockets that were intended to go inside the grease gun, but I couldn't get them to work: they blocked the goop from getting to the business end.
  9. Starting at the bottom hole and working your way to the top, put the grease gun on the packer nipple and inject the goop slowly but steadily. If the goop/foam is leaking back out the packer, that's a sign that you're probably not gaining anything by injecting more goop. It's quite gratifying to see the goop/foam/water being forced out the face of the crack when you inject the goop. You need to use some fair force to get the grease gun off the nipple; don't be afraid to give it a good yank and maybe lever it a bit.

I've uploaded some pictures showing the result on my wall. It's been through a bit since I completed the repair a few months ago (rainstorms, melting snow) and has remained dry. Some of the hardened polyurethane is visible from the outside above ground level, and combined with the polyurethane that forced its way out the face of the crack inside and over the top of the concrete repair, I'm confident that the crack has been sealed from top to bottom and front to back. I'm quite happy with the result.

  • After several months and seasons change, how satisfied are you with your solution? Jul 22, 2017 at 15:26
  • 1
    Well, the repaired crack is now hidden again behind a finished wall so I can't go and check it, but during the several months it was exposed I didn't observe any leaks (including through the wet springtime). I remain very happy with this repair. I've got a bunch of goop and some packers left over, and I'm hanging onto them just in case a similar problem is revealed elsewhere.
    – Paul Price
    Jul 23, 2017 at 21:37
  • Thanks for responding Paul, I may give this approach shot before doing anything more drastic. Jul 24, 2017 at 0:04
  • 1
    All the best! Let us know how it goes. If the crack isn't actively leaking, you can get polyurethane injection kits that are cheaper and much easier to use - no drilling, no grease gun. You mix spread some epoxy (included in the kit) over the crack, and then inject the polyurethane using a caulk gun.
    – Paul Price
    Jul 25, 2017 at 2:06

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