How to Repair Cracks in a Concrete Block Wall

LESLIE: Howard in South Dakota, you’ve got The Money Pit. What can we do for you today?

HOWARD: I’ve got an older, cement-block garage and it’s got a bunk house in there, too. But it’s got a cellar under one corner and I guess I’ve – the dirt had saddled on the outside, so those – the wall on the north and the wall on the east in that cellar was starting to push in. And it made some pretty good-sized separations in the block above the ground.

TOM: Right. Cracks?

HOWARD: And we dug it out and then put – just right in the corner, we put a foundation there and then put cement up and then took two strips of metal, one on each side, with bolts in them. And we got it pulled back pretty good together but there’s still some of those cracks on the outside, in those blocks. And I don’t know whether just putting mortar back in them – I had a guy tell me if he used carbon fiber to tie those together where they would stick to the block …

TOM: Well, look, first of all, Howard, you’re talking about a do-it-yourself structural repair and I can – I appreciate your willingness to attempt this on your own. But that said, it’s not for the faint of heart.

Now, what’s most important to understand is that the structural stability on this is being loaded from the top down. So, a vertical crack doesn’t bother me so much. A horizontal crack, where the wall has the potential of being sort of pushed in, does bother me. It sounds like you’ve dealt with the horizontal crack but you still have some vertical cracks.

What I would do is I would simply seal those vertical cracks as best I could. Mortar is not going to work. You’re going to need to use a sealant that can stick to concrete, like a silicone or something like that. QUIKRETE has a number of products that will work for this. And then once you get that sealed, then you put the soil back.

You need to be very, very, very careful about grading here. The reason this happened is because you had too much water that settled against the foundation. It froze, it expanded and pushed that wall in. If you get the drainage right, that won’t happen again because most of the runoff will be away from the wall and that soil against the exterior wall will stay relatively dry.

So the drainage is going to be really important when you put it back, both with the angle of the soil, which should drop about 6 inches over 4 feet. And with any gutter system that you have on it, you want to make sure that you extend the downspout. Does that make sense?

HOWARD: Yep. I thank you very much.

TOM: You’re very welcome, Howard. Thanks so much for calling us at 888-MONEY-PIT.