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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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    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 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 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 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 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 at 18:15

2 Answers 2

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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.

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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. Jun 14 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.

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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? Jun 14 at 1:17
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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 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 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 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 at 17:53

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