Crazy Looking Spider Web of Basement Wall Cracks Explained

Joseph Coupal - Wednesday, February 05, 2020

In this episode, Crack Daddy himself, Adam Tracy, shares a case study on a pretty gnarly basement wall crack problem. The blog has pictures of these cracks so be sure to visit waterproofing-blog to see them.

Narrator: It’s time once again for the “Crack Man Podcast” hosted by A1 Foundation Crack Repair. We’re here with the Crack Daddy himself, Adam Tracy. This podcasts provides expert basement waterproofing, concrete repair, and preventative maintenance tips for homeowners and businesses. A1 Foundation’s valuable insight will help avert a disastrous flood within the basement, health problems associated with water infiltration within the basement, and protect your biggest investment….your home. The topic of today’s podcast: Crazy looking spider web of basement wall cracks explained. Adam, you sent us some pictures of some of the worst basement wall cracks I’ve seen. What can you tell us about them?

Adam: Yeah this is definitely an unusual case. Most times we get a customer calling us, it’s pretty easy to diagnose what they have. Most foundation cracks in the concrete or concrete foundation are going to go straight up and down, or maybe come off at a slight angle. In some more structural cases what you’ll see is it’ll go more on a horizontal location, may go some deflection, where one side pushed out from another. This particular customer called us up from the Boston area, Somerville. And he calls up and says “I have cracks that go top to bottom, left to right, diagonally.” So I immediately thought, “Well that is a strange scenario, we don’t see that very often.” And I asked them, “Could you please send over some photos?” Because sometimes what is described is not always what is seen in real life. So, I saw these photos and sure enough, he had cracks that went from the top to the bottom, left to right, and diagonally across the foundation and one corner of the foundation.

So, we set up an appointment to go out and take a look at this and found out that part of the issue with this property is the grading on the land. Where these cracks are actually located, are at the entrance to a garage hole under for the house. It’s a split-level house, where the garage is underneath the living space, and the living room above. And on the backside of the house, the grade level goes from 7 and a half, 8 feet of soil down to where the garage floor is, and a very steep drop-off. So, you can imagine, if you’re looking at the back of the house and the land really slopes very quickly, with a retaining wall type of scenario right outside the garage door.

So, these cracks were formed right at the corner of the garage opening, on the very back corner of the house.

So why did these form? What causes something like this? When we see cracks that go top to bottom, we know that most cases it’s the settling crack where the footing has dropped a little bit after the compaction of the soil, or it could be a shrinkage crack when the water and the concrete starts to dry out a little bit, concrete starts to shrink and it causes the stress crack that goes from the top to the bottom. But we know we see a crack that goes from left to right across the foundation of a concrete foundation, usually that’s an indication that it’s a structural issue, where the soil is pushing in. Maybe this was caused by a piece of heavy equipment that bumps the foundation during construction or landscaping events. But when we see them looking like the photos that I’ve sent you, where they go every direction, looking just like you described as a spider web, that’s when we have what’s called “shear force”. Shear force is when the foundation is being pulled across itself against the grain. It’s not necessarily an issue of footing, although I’m sure the footing is being affected here. It’s not necessarily an issue of a piece of equipment, or the soil pressure just pushing against the foundation after a bad foundation pour. In this case, the land itself is pulling the house against where it’s anchored to. So you want the house to stand where it is, and you want the soil for it to go on a different direction, and so were seeing a lot of these shear forces across the foundation, where it’s basically being torn apart at the concrete level.

Narrator: Well, the science of what you guys do really never ceases to amaze me because there’s just so much going on and so much analysis has to be done. So, in a case like this, obviously you’re going to fix the problem with the wall, but do you have to do something with that land on the outside to keep this problem from popping up again?

Adam: Yeah, part of the recommendation is certainly going to have a landscape team put a more gentle grade slope away from this foundation instead of having a steep drop-off against this corner. The lucky part of this particular home is that there wasn’t a lot of deflection in the cracks where one side of the crack is significantly pushed in or out from the other. We saw the shearing of the crack, we didn’t necessarily see a movement of the foundation being pushed in or out. So we’re lucky in the sense that this case. This portion of the house didn’t have to be replaced with a new foundation. We were able to save it by stabilizing the entire structure using a carbon fiber. We flanked it on the interior, which is 10 times stronger than steel and actually reinforces both in the up and down direction and the horizontal direction. These things are used a lot in applications where you have a concrete overpass or a highway, and they need to stabilize the underside of the concrete overpass. They use these to wrap the concrete beams in. This is the same type of material that’s used here in order to stabilize all the pressures that are being forced on this corner of the house. Now if the grading does not get changed or is not affected later down the line here, you will see additional pressures build up further down the foundation just because that pressure has been relieved. But in this case the house was able to be stabilized in this corner without a replacement.

Narrator: Thanks Adam for sharing this fascinating case study. I’m sure the homeowners’ relieved that you’re able to take care of this problem for them. If you have a basement water problem and think you need a professional, or, if you’d like more information on foundation repair and waterproofing topics, please visit or call Rich at (866) 929- 3171. Or you can email rich at Thanks for listening and keep that basement dry.

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A-1 Foundation Crack Repair, Inc. is a fully registered home improvement contractor. Contact us today to talk to a knowledgeable, master waterproofing professional.

Toll Free: 866-929-3171

Call Us Today at 866-929-3171

A-1 Foundation Crack Repair, Inc. is a fully registered home improvement contractor. Contact us today to talk to a knowledgeable, master waterproofing professional.