Fix a small leak in a basement wall

A small leak in a basement wall can scare people off. It looks like it should be an expensive repair and a precursor to all sorts of other problems. But if the foundation is leaking through a chip in the wall, you can fix it yourself for a few dollars.

If the basement wall has severe cracks, you probably need to bring in a professional. Assuming the wall hasn’t moved, you’re looking at a couple hundred dollars to have a professional fix it. If the walls are moving, that’s a bigger issue and definitely needs professional help. But you can fix small leaks yourself cheaply and easily, especially if it’s a chip, not a crack.

If you have small leak in a basement wall coming through a chip like this one, you can shore it up with epoxy putty to fix it cheaply.

Not every chip or crack leaks. That said, even if a chip or crack has been dry for years, it can start leaking at some point. If there’s a weak point in your foundation, water will probably find it eventually, but it can take years. Shore it up, and the water will find somewhere else to go.

A quick fix for a small leak in a basement wall

Chips in basement walls are fairly common, often the result of misguided home improvement projects. To fix one, go to the plumbing section of a hardware or home improvement store. Buy a stick of plumber’s epoxy putty. The no-name brand is usually a couple of dollars cheaper than a big name brand like Loctite and will work just as well. For example, Home Depot sells a brand called RectorSeal for around $4. A 2-ounce stick is enough to fix a pretty large chip in the wall. Look for it in the plumbing aisle, not in the adhesives aisle. The stuff in the plumbing aisle is just as good but costs a couple of dollars less.

Epoxy will cure even if it’s wet, but it will stick better to a clean, dry surface. If at all possible, wait for a dry day when the spot isn’t leaking. Running a dehumidifier will help to dry it out quickly. You can also try hitting the affected area with a heat gun to help dry it out.

Applying epoxy putty to the chip

small leak in a basement wall
Here I’ve applied epoxy putty into a chip to fix a small leak in a basement wall. I need to smooth it out a bit to make it look nicer, but it will keep water out once it cures.

Break off a piece big enough to fill the low spot in the wall. Roll and kneed it in your hands until the color is consistent, with no marbling or lines in it. It will heat up a bit once you mix it consistently. Once it starts getting warm, you don’t have a lot of time left to apply it. Press it tightly into the hole in the wall. If it doesn’t fill it completely that’s OK. Just come back and follow up with a bit more. If you mix up too much and end up with a bulge, that’s OK. Just smooth it out as best you can. A bulge of a few millimeters won’t hurt anything.

If there are other spots nearby, go ahead and fill those in too. If they haven’t been leaking, they may start once you fix the other one.

The epoxy sets up in 15-30 minutes, and fully cures in a matter of hours.

Once it cures, the epoxy remains a dark gray color that probably won’t match your wall. It takes paint well, so you can paint it a color closer to the rest of the wall. For extra protection, paint it and the area around it with Drylock paint, taking extra effort to get the paint into the edge where the epoxy meets the concrete, since that’s a potential spot where any future seepage could occur, if it ever does.

If there are other chips in the concrete near the one you fixed, go ahead and fix those too. If the water can’t escape through the chip you just fixed, it may find another one nearby.

What about cracks?

I’m willing to use this quick, cheap method on chips because I know exactly how far into the wall it goes. You can’t be certain of how far back a crack goes. If you have a crack in the wall and it’s not leaking, you can leave it alone. Not all cracks leak, and not all cracks ever start to leak. My tips for stopping hydrostatic seepage also help keep cracks dry.

If you do have a leaking crack, it’s best to call in a professional. A professional will fix a crack for around $200 and guarantee it, even after you sell the home. A professional crack repair involves injecting epoxy into the concrete to seal the crack all the way through, in addition to applying epoxy to the visible surface. If it ever leaks again, they’ll come out and inject more epoxy and shore up the visible surface as necessary. But recurrence after a professional repair is uncommon.

So while a leaking crack is a more expensive repair than a simple chip, it’s still not a ruinous expense.

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