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Question DetailsAsked on 6/27/2013

my cement garage floor is sinking and cracking who should I call

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4 Answers


First - assuming it is on-grade - i.e. built on ground level, not over a crawl space or downstairs or basement or overhanging a slope. If it is NOT on-grade, you need a structural engineer ASAP, and do not park in it - you have a structural failure in progress. I would also look into my homeowner's policy to see if structural failure is covered, and if so have an adjusted come out to look at it.

Now, for the normal case where it is on-grade - i.e. no rooms or open space under it, and you drive right out onto the driveway from the slab.

1) If minor settling (say less than 1" maximum from center to edge, IN ADDITION to any drainage slope that was already there), with narrow random cracks or relatively straight cracks towards the corners, this could be due to inadequate compaction of the fill under the slab. Unless it is a new house still under warranty, I would not worry unless it is more than hairline cracks (i.e. wider than a ball point pen tip). A normal garage floor, after 10+ years, will probably have 3-8 of these, with some along the edges, and most in the center portion of the floor, commonly radiating out from the floor drain if you have one. Can be washed clean, broken pieces dug out, and patched with garage floor repair epoxy, with portland cement mixed to soft dough consistency and trowelled in, or with concrete crack repair caulk (in a tube, like siding caulk, applied with caulk gun).

2) If cracking is aligned with the center of the slab and opening at the top (rather than spalling or splintering the concrete), then it may be settlement of the rest of the house dragging the slab down and "breaking its back". If cracks no larger than in 1) and not growing noticeably, then I would not worry - repair as above.

3) If cracking and sagging parallel with drain pipe from floor drain, then could have a broken sewer pipe. If keeps sagging more, get sewer and drain contractor to clean and run a camera in the sewer to look for broken pipe, ESPECIALLY if your main sewer pipe exits the house under the garage slab. (There will normally be a vertical about 4 inch cleanout pipe, open or rubber capped or plugged, sticking a few inches above ground level about 2-4 feet outside the foundation wall where the sewer pipe exits the house).

4) If only cracking lightly right at the abutting edge of slab from the house, probably not a problem - house and garage slabs will settle differently, with house settling more because the central part of the house sits on the house slab. This will commonly cause spalling and cracking, and sometimes pulling away, right at the edge of the garage slab.

5) If slab is generally cracking up and pieces are broken free and raising above one another, like a sidewalk breaking up, then you have a general failure of some sort - either bad construction, too heavy a vehicle for slab thickness (like large SUV or loaded pickup on 4" slab), or serious foundation movement. I would call a civil engineer specializing in residential foundations.

Search the List (in green banner bar) for local engineers and reviews. To find which local engineers are Foundation or Residential specialissts you may have to match their names agasinst specialty listings in your local yellow pages.

Feel free to answer here with more description of type, direction, extent, size etc of cracking if you want to get more detailed.

Answered 5 years ago by LCD


I actuallty have this problem, too. I think mine is due to woodchucks. I get at least 2" of water during heavy rains in the front part (the door gets trapped in the ice in winter time). I really don't know who to call either. The bottom part of all the walls are now rotting due to the water....

Answered 5 years ago by Zarine


Garage is lower on sides, causing gaps. What's the best fix?

Answered 4 years ago by n8dogmd


n8dogmd - just noticed your question and photo on this older post.

What I do, and not tough to DIY, ASSUMING your vehicle has adequate overhead clearance coming in so that the buildup will not cause roof scraping on the doorway beam, is to build up a grout sill under the door to fill the gap. Chisel or chip a roughly 2" wide strip (in your case) in the concrete slab right where the door makes contact, and wash it off good to remove dust and chips and to saturate the concrete for good bonding. Using straight portland cement or a patching grout (a smooth or sanded concrete repair patch mix, NOT concrete mix - avaialbe in 1 pound and larger containers) mixed to a thick consistency (thicker than waffle mix - more like bread dough so it will mound up) put down a bead along on top of the roughened concrete more thann thick enough to fill the gap, then cover with a couple of layers of saran wrap or a plastic garbage bag cut into strips to prevent the door from sticking in it. The grout strip has to be thick enough for the door to compress it when it closes, but not so high it spreads out badly and looks unsightly - so will be fairly thin in the center, thicker toward the edges in your case.

Then after the plastic is on it, close the door on it normally. This is where saran wrap is nice - you can see through it to be sure it left an impression in the grout. Open door and make sure it made contact all the way across its width - if not, peel up plastic and put down more grout mix. You can also at this time clean up (with a spatula or putty knife) any excess spread out material making the ridge unduly "deep" (from front to back). Then, when sure the door is making contact all across its width, lower the door again and leave the door down for a full day. After curing that way, I keep wet with wet newspaper or cloth (good wet layer) for at least 2-3 more days to be sure it cures well, then peel off the plastic and the grout sill should match the bottom of the door beautifully. Works especially well with bulb-type bottom door seal strips, forming a very air and bug-tight seal across the bottom.

Do not drive on for 3 days, keep wet during that time - and do not do this in freezing weather because the grout will not cure corretly and will spall off the slab.

Another way to fill the gap, which is also the way to do it if tight vehicle clearance prohibits the grout sill solution, but can be more trouble to my mind especially if you want a real good seal and have a large gap like yuou do, is putting tapered wood strips on the bottom of the door to fill the gap. Of course, easier to do if you approximate the gap with wood, then use a bulb type garage door seal on the bottom to finish making the seal - I use the M-D Building Products seals, available at many box stores and lumberyards.

Answered 2 years ago by LCD

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