I have a house with a floating slab floor built on a cement foundation. There is a crack in the foundation that is 1/8 inch wide which has existed since before I moved in 4 years ago. I never thought it was a problem until a guy (who is in concrete repair sales ) told me I should get it fixed.

Unless the crack gets wider or there are observable problems in the house, I'm considering not addressing it at all. Is this a bad strategy?

If I do wait to fix it, will it likely be much more expensive down the road?

  • 1
    You're title is asking about cracks in the foundation (which in your case is a slab), but your question body describes settling. Which is it? Also, what is "the floorboard"?
    – isherwood
    Aug 12 '16 at 16:32
  • 1
    Depends on the cracks. Photo would help.
    – keshlam
    Aug 12 '16 at 16:49
  • There is a bit of difference between a "floating slab" foundation and a house built on a foundation that also has a floating slab floor. I believe yours is the latter. I would fill that crack with chalk and monitor. If it continues to separate, repairs are in order; if not...
    – BillDOe
    Aug 12 '16 at 20:11
  • Oops! I meant caulk, not caked calcium carbonate.
    – BillDOe
    Aug 12 '16 at 21:31

Small hairline cracks are fairly common in foundations and slabs. They are usually caused by ground subsidence, and typical freeze/thaw cycles. They can also form almost immediately after the slab is poured for various reasons. If the crack continues to open, or there is any shift in the slab, you definitely would want to get it checked out by a professional.

Slabs can be very costly to repair. There are techniques out there such as slab jacking, and underpinning the foundation. These kinds of repairs can be in the tens of thousands of dollars.

Honestly, this sounds like a scare tactic from your contractor to drum up some business. If I were you, I would first fill the crack with a caulk made to fill cracks in concrete, and keep an eye on it. If a full Winter season passes, and there is no change in it, then it should be stable enough to leave it. Just be sure to check it periodically, and inspect for other cracks.


Best thing to do would be to have a structural engineer inspect it. Some of these types of problems are much easier and cheaper to fix early on. Some settling is expected in any house, but it can get expensive in a hurry if it continues, I just watched a home renovation show where they bought a house out of foreclosure, pulled up the carpet and found HUGE cracks in the slabs in almost every room, ended up being close to $50k to fix! I think it would be worth it to have a professional come out and evaluate it and go from there.

  • 2
    Expensive drama on a "reality" show? Crazy.
    – isherwood
    Aug 12 '16 at 18:25

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