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I have a crack across the entire front of my garage floor. I believe that the crack was caused by a poor drainage issue that has been corrected. The drainage issue also caused the pavers in front of the garage to sink.

Although I believe the drainage issue was fixed, I'm not terribly confident in the base under the cracked concrete or the pavers. Would a complete cut-out of the cracked area (probably about 12 inches by 20 feet), repair of the base and replacement of the cracked area be the better of the two options given the base may (or may not) be compromised?

What is the best way to fix the garage floor? Should I cut out about 12 inches of concrete (between the pavers and the main garage floor), tie into the existing floor with rebar and then pour new concrete? Is there a better solution? Is this a DIY project or should I hire a professional? I have some (although limited) experience with concrete.

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Edit 20230117 Just as a follow-up for anyone who might have a similar situation. I ended up using a grinder with a masonry disc to make the thin cracks a bit bigger and then filled the entire crack with Polymer Modified Structural Concrete Repair sold at Home Depot. It has held up reasonably well so far. Thanks for all the help.

UnhandledExcepSean
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Dean
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    Maybe you can help clear things up. On close scrutiny, does the outer edge of your slab appear to be the original concrete or an overlay (possibly to ramp to the pavers)? Look specifically at the ends, near the door track. – isherwood Jun 14 '22 at 14:30
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    I was able to obtain the original plans for the garage and I've added pics to the post. – Dean Jun 14 '22 at 16:41
  • @isherwood - Do a survey of garages in the same general area, and of the same age. You will see many with similar "features". – Hot Licks Jun 14 '22 at 17:09
  • @dean can you show a picture of the inside wall at floor level on one of the sides of the garage door? Basically looking to see how the slab meet ups with the wall, and how the wall sits on the foundation. I did not see an elevation marker for the garage floor or the foundation wall. Based on your first photo it looks like your foundation wall stands proud of the garage floor slab. That will be part of the difference between the 1'-2" drop at the door entrance and the 4" of concrete and 4" of gravel under the slab. Can you measure the difference between slab and top of foundation wall. – Forward Ed Jun 14 '22 at 18:02
  • @dean heck you said you removed pavers and dug down. do you also have pictures of that? Can you confirm if the concrete on the outside of the crack is the same type of concrete as the inside slab? ie different pours, or most likely from the same pour? – Forward Ed Jun 14 '22 at 18:15
  • @ForwardEd It looked like the same pour but not entirely sure. I'll post a pic of that and also a pic of the inside where the garage wall meets the foundation. The foundation sits about 3" above the floor. – Dean Jun 14 '22 at 18:20
  • A lot clear now what is going on and will allow people to more accurately answer, and for you to figure out which answered still apply. It looks like you do have an 8" foundation wall around your garage. Your perimeter walls sit on the outside half of it. Based on the disintegration of top interior portion, I would say you do not have air entrained concrete and you live in a climate subject to freeze thaw. Either that or your foundation was not cured properly. Your garage slab is slightly recessed at the doorway. This is most likely to contain any water that may seep in under the door. – Forward Ed Jun 14 '22 at 18:35
  • Looking at your picture with the paver, and assuming that you have a standard paver thickness of 2"-3" roughly, it looks like you have not dug down far enough yet. I was originally going to say you had a jagged line that distinguished the two pours, but closer inspection shows that its most likely just dirt caked on. You'll need to dig a little deeper, and clean of the edge of the slab a little to get a better understanding of what is happening there. At this time though it appears that the outer edge is one pour. (subject to change) – Forward Ed Jun 14 '22 at 18:42
  • I am highly doubtful of this, but what may be happening is your garage slab is settling at a different rate than your foundation. The slab may be hanging up on the foundation wall. I think this is personally hog wash to a degree as the crack would A) be closer to the interior, and B) the portion on the wall would be higher. Neither of these are true I think. – Forward Ed Jun 14 '22 at 18:54
  • As @ForwardEd said, this looks like natural settling of concrete, and that is something you may or may not need to do anything about. In this case it appears to be mostly cosmetic. Glue isn't a permanent fix by a long shot (although it will prevent water intrusion, which is one of concretes biggest enemies), but it might last long enough for you to pass it off to the next owner (who might fill it with glue again). You should see my garage floor, it looks like the grand canyon compared to yours... – Z4-tier Jan 18 '23 at 04:28

3 Answers3

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Good news, that is not a crack in your garage floor. It's just a damaged cosmetic connection from garage floor to the pawers. Someone already patched it before. Since those are thin, it will not support the weight of the car driving over and over.

You can easily chisel it out (just the loose parts), and replace with some concrete. Use a hammer and gently knock on it, to find the loose parts. Do not start cutting with any tool. No need for that.

There is a fiber reinforced concrete which would be good for that. When buying concrete look at what is the minimum thickness it can be used at. I recommend "Vinyl Concrete Patcher "

Also mist the surface before applying concrete, and mist it afterward for few hour so it cures well.

This is very low cost solution and anyone can do it.

isherwood
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Ruskes
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    @isherwood In general, a crack near the edge of imperfect concrete subject to heavy wear & tear would not be that unusual. I just don't think that's the case here. We'll see once we have more information. – manassehkatz-Moving 2 Codidact Jun 14 '22 at 18:24
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I'd pick a line inside the garage and cut it with a concrete cut off saw (14" gas powered) or use a 7" angle grinder with a diamond blade. Setup a straight edge the saw / grinder can follow.

Break out the old concrete.

Then dig out enough to have at least 6" of thickness for a slab that will bear the weight of a car. Depending on the width I'd add at least one row of rebar with rebar chairs.

The new portion of the slab will crack on the cold join but it will be straight. Compact the base and pour your concrete. Finishing a narrow slab like shouldn't be too hard since you have a reference surface. If you haven't poured and finished concrete before then I'd hire that portion out.

As far as the pavers go you'll likely have to pull them and put down a new base and ensure it is properly compacted.

jwh20
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Fresh Codemonger
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    The concrete so you have a nice line between the garage floor and the new piece of garage slab. Assuming they want a good job otherwise why touch it? – Fresh Codemonger Jun 14 '22 at 01:17
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    My guess here is that the edge of the slab was undermined by poorly compacted fill just like the pavers adjacent to it. – jwh20 Jun 14 '22 at 11:21
  • note: Based on the drawings, the existing garage floor slab is only 4" thick. In addition there is 4" gravel. The foundation wall was dropped 14" at the garage door opening. This would leave 10" of "SOMETHING" – Forward Ed Jun 14 '22 at 17:09
  • @ForwardEd - it's hard to read but I think the plans say that the foundation was dropped 1-2" at the garage door opening. I did remove a few pavers and dug down 6" and couldn't find the "bottom" of the concrete. Also, the plans indicate that the foundation is 8" wide but the portion of the concrete that was dropped down 1" below the rest of the garage floor is just over 12" wide. So some portion of that is not on the foundation. – Dean Jun 14 '22 at 17:35
  • @dean normally plans don't give a vague range. So it should not be 1" - 2". It is most likely 1'-2" for 14". It is actually quite clear. you can see the tick for the foot indicator right above the dash. it really should be closer to the 1 but no one is a perfect drafter all the time. – Forward Ed Jun 14 '22 at 17:53
  • @ForwardEd Apologies. You are right about the 14" drop. My ignorance is on full display. – Dean Jun 14 '22 at 18:17
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Just as a follow-up for anyone who might have a similar situation. I ended up using a grinder with a masonry disc to make the thin cracks a bit bigger and then filled the entire crack with Polymer Modified Structural Concrete Repair sold at Home Depot. It has held up reasonably well so far. Thanks for all the help. Dean

Dean
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