Understanding slab foundation split in half

18 Replies

Hi folks, 

I'm a DIY'er myself and I picked the DIY section so I can learn from the experience of other hand-on folks. I'm trying to understand the approach to recommend to my foundation guy.

I'm working on a BRRR property with a foundation cracked along a straight line. Here's a picture and video explaining it.

It's as bad as this sample image: 

and here's a video of the crack: Video of crack

Wondering if anyone has any ideas of the approach to fix this. I know the foundation guys will be able to lift it up, but I'm trying to understand how to 'join' the cracked parts together so it can make a stable floor and be a reliable rental property.

Thanks!

So if you were selling it for a flip, I would be worried about an inspector perhaps squishing your hopes of profit if there is evidence to be seen. However, you are renting this. An appraiser for refi does not really care about a crack in concrete (happens all the time). I would just make sure there isn't going to be movement, water penetration, or bug penetration. The latter two can be accomplished with some PL concrete sealant. Unfortunately I do not have the expertise to advise on making sure there is not going to be movement. If the structure is safe and the crack will not impact finishes (i.e. you are not putting a tile floor over it that will just crack too) then I would not focus too much on making it perfect in a rental. If an engineer says this was from settling and there is not further risk, I would come back with a grinding disk and take off any high points, then a crack chaser wheel to clean it up, and then put in a backer rod if needed and top with a self-leveling PL sealant. Let it dry, then underlayment and LVP as a floating floor in case there is movement. Now if the engineer says it is not sound, you are out of my league. Best of luck!

I don't have much experience with foundation/ slab repair but you have quite a significant crack in that slab. This is no backer rod and filler type deal. I wouldn't recommend doing this sort of work yourself or at least consult a foundation specialist. Doing this incorrectly could cause some significant problems with different parts of the house settling faster than others.

@Milind Shastri a crack in concrete isn't necessarily a problem. The issue here is the crack runs the entire length and appears to reveal settling on one side of the property. It may seem logical to support the side that is moving, but in some cases that can make things worse. If you stabilize a portion, the rest can still move so it is usually best to support the entire slab. Assuming this is a monolithic slab (no footings), the real question is how much this affected the housing structure. You can put a laser level on the siding and see if one side is lower. The fix could be as simple as filling the crack or as complex as adding piers. The piers can be inserted through holes in the concrete and go deep enough to find stable ground. It is not a DIY project. You want foundation experts that have been around a while and offer a guarantee. 

Like I said, it could be as simple as just filling the crack. Figure out why it moved, how much it moved and if it will continue to move.

@David Lee Hall, III , @Joel Calkins , @Joe Splitrock , thanks for the suggestions! Being in TX, foundation cracks are pretty much the norm. I've handled worse on flips, but usually, piers have done the trick. However, in this case, I'm prepping up for an out-of-state rental and trying to avoid getting a sewer line/gas line leak from the sunken side breaking off from the rest of the slab a few years from now (PS: I will not mind if you think I'm being too anal). 

Really curious to see if there are ways to 'bond' two broken halves of a slab together in a way that the joint halves provide structural support to each other. With the risk of sounding like a nut-job, I'm wondering in addition to installing piers to level things out, an approach such-as scooping out chunks from either side and dropping in some rebars for binding strength and pouring cement back (kinda like stitching a wound) could work. something like this: 

Texas! Yes I have seen a few of those broken slabs when in Dallas for training. I think I have only ever seen one here in Pittsburgh. Not being an engineer, my thought would be what they do on highways around here which is similar to your drawing, cut out the crack on both sides, drill and epoxy in rebar, then back fill with concrete. Not something I have ever tackled and I would recommend an engineer consultation.

Is this a basement slab or at ground level? Cracks in slabs are normal, but a crack of this size indicates ground heave (as opposed to vertical cracks in a wall indicating settlement). If this is at ground level, and depending on what your winters are like in Texas, I would suspect this is the result of annual freeze/thaw cycles, in which case there may be no getting away from the problem without serious renovation work. If, however, this is in the basement below frost line, it could be the result of poor backfill of stone base when the slab was first poured. @David Lee Hall, III described the perfect remediation in his first reply to take down the high points and follow with a crack chaser. I would recommend not using backer rod and instead filling solid with a high strength non-shrink grout. Either the slab is still moving or it's not, and if it is still moving no matter what you put in there it's going to crack/pull away, even with the rebar "stitching" method.

Originally posted by @Milind Shastri :

@David Lee Hall, III , @Joel Calkins , @Joe Splitrock, thanks for the suggestions! Being in TX, foundation cracks are pretty much the norm. I've handled worse on flips, but usually, piers have done the trick. However, in this case, I'm prepping up for an out-of-state rental and trying to avoid getting a sewer line/gas line leak from the sunken side breaking off from the rest of the slab a few years from now (PS: I will not mind if you think I'm being too anal). 

Really curious to see if there are ways to 'bond' two broken halves of a slab together in a way that the joint halves provide structural support to each other. With the risk of sounding like a nut-job, I'm wondering in addition to installing piers to level things out, an approach such-as scooping out chunks from either side and dropping in some rebars for binding strength and pouring cement back (kinda like stitching a wound) could work. something like this: 

 I would not do this. The crack occurred at a stress point. Rejoining the stress point without addressing the issue could make it worse. How old is the property and using a laser level, can you see any movement of the structure? Shoot the laser level on each corner and see if how much higher one corner is versus another. 

Originally posted by @Brian Ploszay :

Very common in parts of Texas from my understanding.  For a rental property, the solution is a bit easier.

YUP its not if  its When in parts of Texas no doubt and in MS  especially the Jackson area with the Yazoo clay .. especially rentals when the foundations must be watered in the summer and the tenants fail to do so.

its something landlords need to factor in.. and also have cap ex reserves.. 

 

@Milind Shastri

You pretty much have only two options here. 

1 - Doing what your foundation guy is suggesting. This is basically jacking up the slab, filling in the voids with grout and then epoxy the the joint once its back in place and the crack is smaller. 

2 - Do the above but instead of epoxy in the crack you saw cut back the slumped slab about 12" from the crack. The drill holes in both sides and epoxy rebar in to tie the slabs together. Then pour new concrete to fill the gap. 

The first option is cheaper but unless your foundation guys can pin-point exactly where the failure occurred you have a change of it happening again. If this is just a small section then its probably not going to happen again but if its the entire length or larger area you have a decent chance of failure again. 

Just an FYI. This is why it is common practice now to have a reinforced slab. So even if there is settling it takes A LOT to actually crack the slab, and near impossible for it to separate without a whole building failure. Obviously older buildings didn't do this. 

What does your structural engineer say?    That would be my first point of contact.   That is a tough looking crack and probably a tough one to fix.  Looks like Irving, Carrollton, or Plano to me.   Sometimes I wonder if there are longterm solutions to this big cracks....let us know what works.

@Milind Shastri that's what we did to the foundation in the basement and the beginning of the foundation in the garage. Make the crack bigger. Take a drill or hammer drill that can put holes in the concrete. Of the foundation is 4 inches thick, drill holes about half way (so 2 inches) from and set the rebars inside. The rebars don't need to meet the other side of the wall. Do the same to the other side. Pour concrete.

Originally posted by @Bruce Lynn :

 Sometimes I wonder if there are longterm solutions to this big cracks.

Hi Bruce, this was very close in Garland. I wonder that too. In all the reading I did understand that tacking the source of the problem (seasonal cycles, nonuniform moisture levels, plumbing leaks, poor pours, etc) is critical.

 

Hi, Texas spacially Dallas and Ft Worth is well known for slab cracks, and what you show is the right approach. Get good advice on how to prevent further issues. I remember in Dallas years ago they told me that you need to keep the ground around the house moisture or with plants to prevent the 110F plus days drying the ground to much .

https://www.nachi.org/foundati...

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