How to Fix a Basement Leak: DIY Basement Wall Crack Repair That Even Novices Can Do

Updated on August 9, 2019
Maren Morgan M-T profile image

Maren is a one-person fixer of "TLC Needed" houses. She explains methods simply to homeowners who are not in the construction trades.

Fill Those Cracks!

One paint which fills cracks in masonry is Drylok brand.
One paint which fills cracks in masonry is Drylok brand. | Source

Necessity is the Mother of Learning New Skills

I bought a house. The house had challenges.

When I looked around to see who could help me repair it, I observed me, myself, and I. This was not necessarily a BAD thing, but it required learning new skills.

I didn't exploit my wonderful neighbors by trying to induce them to do my work, but I did talk to them for advice. They gave me great suggestions and product recommendations. THANK YOU, ALL!

Here are the happy results of my crash course in basement leak repair.

Observe, Observe, Observe

In real estate, the mantra is "location, location, location." I say that house repair requires looking, looking again, and then REALLY observing over time.

Among my wet basement problems, one easy-to-spot challenge was a front corner which got a puddle of water every time it rained.

Following are the observation steps I took, sometimes even photographing the site. (With cell phones, it's easy and valuable to record problems.)

1. I checked this corner several times a week unrelated to outside weather. I wanted to determine if the wetness seemed primarily rain-related or possibly connected to super-saturated soil in my yard.

2. Every time it rained, whether lightly, medium-ly, or heavily, I ran down to the basement many times to see if and when the puddle appeared. [It turned out that even light rain started the wetness in that corner.]

3. Every time it rained, I ran down to try to determine where the wetness started.

4. After each rain event ended, I carefully cleaned and dried the corner so I could start with a blank, clean slate for the next observation.

First Guesses

If this was a seventh-grade Science Fair project, I would call my guesses hypotheses. See, gang? That Science Fair methodology really can be applied to real life!

My first set of observations was that the puddle increased in size immediately during the lightest of rains. Since I had just put on a new roof, with careful attention given to the decking underneath the shingles, I was ruling out leaks from the roof above causing the basement problem.

For my first anti-wetness step, I decided to paint the corner both inside and out. I recommend this as a strategy for you, too.

Use the Right Paint

I used DRYLOK (R) Latex paint. I will always opt for a latex paint over an oil paint due to the ease of cleaning up afterwards with only soap and water. This Drylok paint is white and looks and feels as if a bucket of sand is mixed into it. That "sandy" feature is excellent because the sandy bits are what fill the tiny pores and crevices. Look for Drylok or something else especially designed to fill cracks.

(All in all, by the end of the process I used about three gallons.)

Painting the Wet Spot On the Inside

Clean it thoroughly - and this is no small task.

Brush away all loose concrete bits, insect carcasses, dust, debris, etc.

Even vacuum the wall to get the tiniest bits of dust out.

My first observations led me to think that water pushed in at the joining of the concrete floor to the cinder block wall just in the front corner. The corner even seemed depressed (as in dipping lower, not clinically sad). I cleaned, dried, and applied Drylok about 3 times on the two adjoining walls and about one square foot of the floor where the puddle appeared . (Please note: this floor painting is probably not an approved use of the particular style of Drylok which I used.)

My Buddy

A can of Drylok (R) masonry waterproofing paint sits patiently on old wooden stairs.
A can of Drylok (R) masonry waterproofing paint sits patiently on old wooden stairs. | Source

Do Light Painting Work Outside at the Leak Site

I did not think it necessary, nor did I have the time and money, to do an entire French drain, PVC pipes, or other complicated projects to lead water away from the foundation of my house. However, since the property had been neglected, I figured that a little painting of the unpainted foundation could only help.

At the corner of the leak, I dug about 4 inches of soil away and allowed time for the cinder block foundation to dry. Digging down 4 inches is not, or hopefully should not be, difficult for you.

Then I painted the exposed area with Drylok.

After it dried for a few days, I pushed the soil back in place, taking care to make it slope away from the house.

This is not rocket science. You can do it.

Observe with Your Nose Next to the Wall

Obviously, in a mission to stop leaking basement walls, one checks frequently to see if the corrective measures work. And so I did. And so should you.

I was able to see a reduction in the puddle size, but it still re-appeared. However, as I applied a coat of regular primer on the wall, quite closely, I was amazed to find a horizontal razor thin gap in the cinder block course about 30 inches (76 centimeters) wide and 1/8 of an inch (half a centimeter) tall.

Sweet Expletives! This explained quite a bit. The reason I had not spotted it earlier was because it was below my eye level, and the upper row of blocks at this gap actually formed a half inch (1 centimeter) cantilever-style overhang above the next row. Whoever heard of a side wall that was not a level plane?

Holy Moly! So, this is why I say one's nose must be within 4 inches of the suspected leak area. It is not for the purpose of smelling the problem; it is for a very close visual inspection.

Next Step: Concrete Patch

All righty then, it was time to fill in obvious gaping holes with concrete. I used QUIKRETE brand. There is also a pre-mixed form of it, but I don't mind mixing up the amount I need in an old soup can. All you do is add water and stir! Just follow the directions and fill the hole.

After a few days of allowing the patch to dry, I repainted this area with Drylok.


Quikrete is as easy as playdough to use.
Quikrete is as easy as playdough to use. | Source

More Observing, More Discoveries

As I once again had my face up close to the wall while applying primer where the house sits on the cinder blocks, I was appalled to see little pinpricks of sunlight.This is not supposed to be. The house should not have gaps, however small, along its connection to the basement. These leaks obviously contributed to cold temperature in the basement (I live in a 4-season area), and perhaps was permitting moisture into the basement. They had to be closed.

I used a spray foam sealer: GREAT STUFF Gaps and Cracks Insulating Foam Sealant (TM) to fill those holes. Warning if you've never used this sealant: it expands immediately, so you apply less than you think is needed and then watch what happens.

Then for good measure, I stuffed empty plastic grocery bags in those spaces to provide further insulation.

"Great Stuff"

This stuff gets yellow, bubbly and hard.
This stuff gets yellow, bubbly and hard. | Source

Less Water, But Still There Is Water...

The good news was that the puddle became smaller when it appeared. The not-so-good news was that there was still water in that corner. So, be a Sherlock Holmes. Keep watching. I continued with step 2 from above:

Every time it rained, whether lightly, medium-ly, or heavily, I ran down to the basement many times to see if and when the puddle appeared.

By doing this, I was able to see that a tiny trickle of water started at 2 pinholes in a cinder block about 30 inches above the floor. They were like 2 little vampire fang puncture holes, only ten inches apart. Very strange, but I didn't care --- all I cared about was closing them. After cleaning and drying them, I applied several more coats of Drylok to the area.


Of course, I kept observing after this step.

In dry weather it was dry.

Then, my area had a large rainstorm which dumped 2 inches of precipitation in 24 hours.

Guess what?


Persistence, Continual Observation, and Changes

If my 57-year-old, non-construction-experienced, stubborn self can fix a basement leak - you can, too!, Be stubborn! Be persistent! And keep examining and attacking the wet spot until it is gone.

You got it! But...

As we all know, the earth shifts, ground water adjusts, and an underghround channel of rain may decide to visit your repaired basement foundation. Do not regard it as personal failure if a little moisture reappears a few years after your fix. Be ready to use all the same steps again.

Climate Change, More Frequent And Severe Storms, More Flooding

I never thought I'd see what is happening with weather and climate in my lifetime.

Insurance companies and the U.S. military are totally aware of the changes in severity of storms, temperatures, and coastal submersion.

I am sad that more of us will need to be using the skills in this article.

However, I'm glad to pass along the knowledge and hope it is a temporary Band-Aid (TM) while we all all do more to mitigate and reverse the global warming and its consequences.

Please do something for future generations.

Steps for Stopping a Basement Wall Crack Leak

  1. Observe the problem area frequently.
  2. Apply a masonry waterproofing paint as many times as needed.
  3. If possible, grade soil to slope away from the house.
  4. Fill larger cracks with concret patch or foam sealant.
  5. Apply more waterproofing paint.
  6. Continue observations, problem-solving, praying, and painting until the area stays dry.

It Is Possible That You Have a Big Problem

If the described steps don't work after several tries, you may have a bigger problem than the one I conquered. If that's the case, please start shopping for bigger guns (pros) to help you.

Maren E. Morgan will continue to share her adventures in house re-habbing. If this article helped you, I am very happy. We're all in this together.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

  • Can we put a coating of stucco mix over drylock and then reseal with drylock?

    It sounds do-able to me.

© 2013 Maren Elizabeth Morgan


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    • profile image


      3 years ago

      I'm currently fixing a leak in my basement wall. It has a great big gob of great stuff sprayed on there from the previous owner. I've painted drylock but when I get close to the great stuff the drylock seems cause the great stuff to pull away from the wall and that original leak has started again. I'm tempted to paint more drylock on the leak, but am worried the great stuff will react? Not sure if any of that made sense, but since you used both I was wondering if you had experience with this?

    • Maren Morgan M-T profile imageAUTHOR

      Maren Elizabeth Morgan 

      4 years ago from Pennsylvania

      Hi. First of all, DryLok is NOT approved for that use on the floor. I used it only in one corner and mostly on the wall. The part on the floor was probably 2 sq feet at most. The wall took repeated applications! I would advise you to look at all the kinds of Quikrete products available now. Best wishes.

    • profile image


      4 years ago

      You said you used 3 gallons of DryLok for your basement. Was it your entire basement? What are the dimensions? I'm looking to reseal my mom's floor and need a guesstimate of how much I'd need if i used that product. Thanks!


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