Garage floor foundation cracked, preventing door from closing

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    I’m a DIYer in NJ, but have more experience than the average homeowner.

    We have a garage where the floor has cracked and shifted, preventing the main garage door from closing properly. It’s high on one side.

    I had a mason come and he cut out a 2x20ft section of the floor where the crack was and pour a new foundation in that space.

    The problem is that the work he did wasn’t level. It was more than an inch high on one side, which obviously still prevented the door from closing properly.

    Afterwards, the mason claimed my issue was with a crack that was allowing rodents to enter the garage from the outside, and while that was a concern, it wasn’t my main concern.

    He tried to argue that “we did the concrete as you tell us to do just to close the gap.” He said the floor is not level “because you said that you wanted to close the gap under the door, the door was like that and you didn’t notice” which is complete nonsense.

    My question is – under what circumstances would I ever have to instruct a mason to pour a level foundation? Is there any validity to his argument?

    Please let me know what other information I can provide to help.

    North Bay, ON

    As you have explained it, I believe your issue is with the mason. It seems to me you have a communication problem and not a technical one.

    BE the change you want to see.
    Even if you can’t Be The Pro… Be The Poster you’d want to read.


    Is your garage door header and jamb opening level plumb and square?

    Honolulu,, Hi.

    Maybe you floor is all out of level so he may have had to pour the mud from bang to bang and the heck with the level. If your door is rubbing on the bottom grind the concrete down or cut the bottom of the door or do some thing that will make it work. It shouldn’t be that big of a deal.


    Yes, I believe this is completely the fault of the mason. I just can’t imagine a mason ever pouring a foundation that wasn’t level, for any reason.

    The garage door and jamb are both plumb and level. I had a garage door expert come and evaluate it (in addition to just using a level myself), and he agreed it is not the fault of the door.

    I’m curious about the comment about it being a communication problem. Should I have better communicated to the mason that I wanted the floor to be level when he was done?

    They are definitely trying to make the point that my request was not communicated to them properly, but I think it’s an excuse. I first explained I wanted a 1″ strip the length of the door (from left to right) cut out with a saw so the door would close properly. It was their suggestion that they cut out the 2′ rectangle and pour a new foundation, so my intention was clear.

    I didn’t ever tell them to make sure it was level, but how could they possibly not know to do that??

    Honolulu,, Hi.

    Yes, I believe this is completely the fault of the mason. I just can’t imagine a mason ever pouring a foundation that wasn’t level, for any reason.

    Then you have really very little experience with cement.


    Pictures would help a lot.

    Boys and girls, this is the problem with trying to GC your own project, when you aren’t a builder and don’t know anything about construction.

    Not a dig on the OP, but there is a reason the professionals do what they do. I would completely suck at rebuilding my boots.

    If you know what the problem is, and what the best solution for a fix is, then you can instruct your subs exactly what to do.

    If you don’t, and you rely on some specialty trade contractor to come up with a solution, then results will vary.

    If you hire a mason to fix a garage door, the concrete might only be part of the problem. So the mason is going to do what he thinks is best, from a mason’s perspective, not necessarily from a total project perspective.

    In addition, when you hire someone to hack in a fix for something, without spending the time and money to do the project completely and properly, you’ll run into situations like this. Maybe a non-standard approach was the only way to do half a job.

    Personally, I decline work like that. If I’m not going to do the job correctly and completely, and if I’m not in charge of the entire project, I pass on doing the work.

    But some photos of what is going on might help us to give you a little more info.


    I’m still confused about the facts of the case.

    On the one hand, you keep mentioning “foundation”.

    On the other hand, you stated that you were only concerned about where the garage door meets the concrete… the “sill” if you will.

    The sill is not the foundation. There is no load path from the structure to the sill. Homes are routinely built and standing with no garage floor poured at all, but there are stem walls, piers, and/or grade beams supporting the engineered jamb walls (either prefab units like Simpson Strong Walls, or site built sheerwalls sheathed front and back with a really tight nail schedule 3″ oc).

    To try and reconcile the confusion concerning your story, I have to ask, did the contractor who did the 2′ by 20′ cut and repour dig out from underneath the door jamb shear walls? Since a garage door is typically only 16′ wide, it would appear so, but it isn’t clear.

    Are there piers poured under the jambs? An inverted T? Was the actual foundation supporting the short shearwalls on either side of the door left alone, and the 2’x20′ saw cut performed immediately behind it?

    If the final grade of the new slab section is 1″ higher than before, does it meet up smoothly with the surrounding slab it was cut from?

    Is the crack still there? How old is the structure? How long has settling had to take place? Has there been a change in drainage? Have you investigated the possibility of continued settlement?

    Most people address door issues as Dirty suggested… shave the door to match the grade. You chose an expensive way to close the gap, and I’m wondering if that money should have gone toward addressing the settlement?

    Does the garage slab float separately from the perimeter foundation?

    So many questions… which is probably why internet diagnostics doesn’t work well for these types of issues.

    Honolulu,, Hi.

    When I posted I thought it was a swing door not the roll up for the car door.

    Owatonna, MN - Minnesota

    While the OP is a little short of details and a photo would help, here is my take on this. Unfortunately I do have to make a few educated guesses.

    the garage is a freestanding structure that is build on a foundation consisting of a thickened slab and not a stem wall with frost footings. The reason that the slab cracked is that some frost got under it and heaved a portion of the slab. the frost acted on the slab differently in different areas causing one side of the door opening to heave and not the other. When the frost came out of the ground, that side did not settle to it’s original position.

    The mason cut out the thickened slab through the doorway, recommending the 2′ width to get past the thickened portion of the slab. He poured the floor and thickened edge back matching the floor in the heaved condition to make the transitions, on each side of the door, match the concrete that remained.

    Without specific direction and noting that the door would not close properly due to one side of the existing, but cracked, floor was out of level and that the ultimate goal was not to match the existing floor but to make the portion of the floor that the door seals to level and square, leaving a “step” on one side of the door. I can easily see how this would happen and how a lack of communication and a full assessment of the problem with the mason would result in him matching the existing floor with the repairs, instead of making the modifications, which would be unsightly and possibly a trip hazard. I am sure he did what he thought was right with a limited knowledge of the problem.


    Okay, thank you for the explanation. I do now see there is a circumstance where the slab could be poured without being level. I thought I explained what I wanted well enough, pointing out the problems that I saw, but perhaps I didn’t.

    I spoke with the mason the other day and offered to cover the cost of removal of the concrete from the new slab and the new material (rebar/concrete, etc) that would be needed to do the work over. He agreed, but said he can’t do it until the spring because of the frost season here in northern NJ.

    This project started by me asking him to cut a 1″ strip from one side of the door to the other to account for the portion that had shifted over time, to allow for the portion of the door that was hitting the raised portion of the concrete to sit in an existing 2″ wide groove that was already there. It would then at least close completely.

    After I explained all this to the mason, he came up with the idea that it would be better to remove the 2′ by the width of the door (which I think is 20′) and I agreed.

    The new slab is level with the apron on the left side of the garage, but it’s higher than the apron on the right side – the side that is clearly too high.

    I’ve attached three pictures here. The two with the red lines show a trough that was created in the apron and extended into the old slab inside the garage, I assume to allow water to drain, before it was redone with the new slab, but was allowing rodents to enter through the small trough, especially with the slab having shifted.

    The other picture is showing the gap that’s resulted from the door not being able to close completely because the slab is at least 1″ too high on that side. The door on the other side, where the slab is 1″ lower, at least closes flush with the left wall.

    Fort Lauderdale, Florida

    So…have you determined the cause of the crack and out of level with the slab? Is it frost heave? Giant tree roots coming up, or differential settlement from poorly compacted subsoil? Or Godzilla passing by underneath?


    It’s conceivable it was giant roots, but the only tree that could have caused it has long since been taken down.

    My best guess is that it was due to frost heave.

    I believe it was level at some point. Perhaps I should have checked it for level prior to it being busted up and repoured, but I was only thinking of the new slab, which would have been level.

    The new slab is at least an inch higher than the outside apron on the right side. You can also see from the picture that there’s still a 1″ or so gap between the inside slab and the apron.


    I feel like I’m looking through a soda straw while trying to reconcile the details shown in your photos in context with an as yet unseen bigger picture that would reveal existing extenuating circumstances which would inform a course of action for the best possible, least costly outcome.

    On the photos alone, it appears one could surface grind the hump between the hand drawn red lines that seem intended to suggest a cause for the door not closing all the way on one side.

    But the wetness in the area calls attention to a bigger picture… one of drainage. What is the surface runoff management plan away from the building?

    Already I see a good reciepe for jam rot in the photos provided.

    Owatonna, MN - Minnesota

    We do not build anything on a slab without a course of block on top of the slab to give a separation from the wood framing to grade. Having a course of 8″ block allows for a good 7″ of separation and helps greatly.

    It pretty much eliminates the jamb rot we are seeing in the photo’s and gives a much more rot resistant structure.


    Hi, thanks so much for your continued help. I’m only now seeing this – for some reason this site doesn’t alert me to new messages. (I’ve checked the “notify me” box)

    I’ve created a video to help clarify some of the comments that have been made. Hopefully this helps.

    The surface wetness is because the seal on the bottom of the garage door desperately needs to be replaced. Water inside the garage door is otherwise not a problem.

    Can I ask you to view this brief video?

    If that’s not possible, I’d be happy to answer any further questions directly.


    The link leads to an error message that states “We are processing this video. Please try again later”.


    Okay, it’s apparently been processed and ready now – thanks!


    Hi all, thought I’d see if anyone had any other thoughts on this?

    After watching the video, do you have any follow-up questions to try and determine how to get the garage door to close properly?

    Columbus, Ohio

    If you’re just concerned about the gap between the floor and the door and you’re okay with a quick fix, you can get 2 pieces of long cardboard and tape them to either side of the bottom of the door so when closed the cardboard is flush with the floor. Put the door up until you can see the new channel along the bottom of the door. You can fill the channel with a gap filler insulating foam from any hardware store. Let it dry for about 30 minutes to an hour and then you can cut away any excess, remove the cardboard and paint to match the rest of the door. The door should now close and seal preventing any rodents or debris from entering.

    Not the most luxurious solution, but apart from pouring a new floor it’s a quick, cheap fix.

    Good luck!

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