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Driveway Is Separating from Garage

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Skeezix

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My house was built in 1982. It has a concrete driveway and a double garage. Over the years the driveway had cracked and slid about an inch away from the garage. I tried using the gray styrofoam-like filler and some caulk, but that of course didn't hold, so in 2015 I had the driveway removed and then re-poured. The concrete guy put in one of those dark gray heavy paper-like things as a separator.

The separation continues and I now have another 1-inch gap between the driveway and the garage slab. The separator is gone. The concrete is 4 inches thick. It appears that the separation will continue no matter what I do, so what is the best way for a DIYer to fill this gap?
 

Snoonyb

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The separator is called an expansion joint and is used to prevent cracking at that joint, because concrete swells under heat.

I'd use the sika-flex concrete filler with an aggregate, sold at most big boxes.
 

bud16415

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Is your driveway on a slope? Maybe clay soil. It is odd to me it is moving in one direction and growing.

About all you can do is fill the gap as it grows.

I'm not an expert but I think I would use a product called Cement-All do a search the big home centers have videos of using it for different fixes. It can be mixed in a 5 gallon bucket and poured in the gap.
 

kok328

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I have the same problem but, realize I'm not going to win the fight against a 1 ton slab of concrete.
The solution that has worked for me for years is to pour fine, screened, clean, dry play sand into the opening.
The first time I did it, it swallowed up and entire 40lb bag of sand. Wasn't until a few years later I had to repeat the process but, only used a 1/2 bag of sand. That was about 3 yrs. ago and doesn't appear I'll need to add more any time soon. The slab really isn't moving that much (if at all) anymore.
 

Skeezix

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Thank you for your replies.

Yes, the driveway slab goes down and away from the garage slab. And yes, the soil here is clay. :(

I'm not familiar with sika-flex or how to use it, nor do I know anything about Cement-All.

At this moment, filling the gap with sand sounds like the best solution. I'm just a little worried about water getting into it but I guess it won't hurt. It's been getting into it over the last 25 years...
 

68bucks

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I did the same thing with the play sand and then used the Sika flex over that once the gap was filled to about 1/4" depth. I had several slabs where that was necessary. I also beat on it with a rubber mallet to get the sand to settle in. I would have to repeat this every few years. I would use a flexible product regardless. A risged materlial will just crack. There is obviously movement there.
 

tomtheelder2020

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So, starting with the driveway slab tight against the foundation, it took the slab about 30 years to move 1 inch. The new slab, poured with a control joint that may have allowed water in, then moved 1 inch in 5 years. There are a number of issues that could be involved but, where there are soil problems, letting water in is almost always a significant part of the problem*. Fill the crack with whatever you want but cap it with something that will shed water. If new cracks develop in the slab, seal them too.

*based on experience in former life working in geotechnical engineering.
 

Skeezix

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I dunno. The separation is 5 inches deep and 16 feet long. I also have another place that is again, 5 inches deep and is 9 feet long. How far will 10.5 ounces go? Seems like I would need a lot of 10.5 ounces of Sikaflex to seal all of that.
 

Snoonyb

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See post #6 and after the sand has tamped down, then the amount of sealer needed will be substantially diminished.
 

oldognewtrick

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You can place "backer rod" in the void and caulk over that. It's a foam material that comes in different thicknesses and available at most big box stores. Caulk mfg's reccomend only a certain thickness of caulk, look on the package to see their reccomended maximum application.
 

68bucks

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You want to fill the gap with the sand to about 1/4" - 1/2" deep to cut down the required sealant. Spread it out in the sun and get it good and dry so it will flow in and fill as much as possible. I'd shy from a backer rod if it leaves much of a void underneath it.
 

Skeezix

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I had forgotten all about using sand. I'll give it a try.
 

bud16415

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I know there are many opinions on how or what causes the movement. The most likely for me is the freezing and thaw cycle with the water trapped in the area expanding. For that reason and if the OP lives in a freeze thaw climate I don’t care for the sand filling method. The sand will hold water and the more water in the area the greater the expansion.



That’s why my suggestion was the Cement All product that will pour into the void like soup and harden like a rock. Hardly any void to collect water thus nothing to freeze.



You could pour the product in and then seal the top of it for extra protection with something but I don’t think I would.

Any way that’s my 2 cents coming from the pot hole capital of the world. :)
 

68bucks

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I live in NW Ohio so we get a lot of freeze thaw. Anything ridged will crack, 100% guaranted. You have to have something that will give. The sand and flexible caulk method will last a couple years or so, then you do it again. I know of no 1 time fix it forever product or method. You have freeze thaw, you have movement.
 

Skeezix

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Thank you for all of your comments and replies.

I think I'll cheap out and use sand to fill the gap. Careful measurement of the gap is 3 inches deep by 3/4 inch wide by 15 feet long. The area doesn't get much water at all and if I have to top it off every couple of years that's okay with me.
 
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fill it, up to about 1/8 or 1/4" from the top, then top it with Sika driveway crack filler (Home Depot sells it), and it may last MUCH longer.... make sure you DAM up the ends, as it will run out any crack it can, as it "self-levels"
read directions on Sika container for correct distance, etc
 

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