Found cracks in concrete slab, how worried should we be?

Submitted by fireaway199 t3_z8il67 in DIY

Here's some photos: https://imgur.com/a/6iYRUuO

We are doing some DIY renovations so we ripped up the tile in front of our fireplace and found a small crack in the slab below. We are also building a new kitchen island. After removing the old one, we found some even larger cracks. Additionally, in both places the slab is far enough from flat that you can see it without putting down any kind of straight-edge.

We are planning to have the floors redone in 2 months (by a pro, not DIY) so we'll get a big reveal of the state of things when that happens. But I'm wondering how worried we should be and if we should get someone in here sooner to take a look at things? Plus, we need to finish the new island before they come to do the floors so this area at least needs to be dealt with before they come to do the rest of it.

Other things:
The house was built in the mid 90's.
What is going on with the caulk(?) where the wire comes out of the concrete? Is that normal? I had been expecting to see some kind of conduit.

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Comments

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Nosferatu-87 t1_iybsc6l wrote

Not at all, all concrete slabs of any real surface area crack.

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KRed75 t1_iybsid4 wrote

Concrete cracks. It's what it does.

You can fill the cracks with epoxy or self leveling polyurethane caulk if it makes you feel better.

One thing I highly recommend you don't do it install tile. No matter what you do, the tiles will also crack eventually.

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Fabulous-Search6974 t1_iybtudt wrote

So worried. Do NOT under any circumstances step on a crack.

If you do.

You will break your mother's back.

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Helgafjell4Me t1_iybv5l9 wrote

Replying to KRed75 (#794,805)

You can prevent that by properly leveling the floor and then using an isolating or "decoupling" underlayment like Ditra over the concrete. Any major movements are likely done happening for a 30 year old slab. Minor movements can still happen and Ditra helps protect the tiles by providing some level of elasticity underneath the tile. Where I think you can about guarantee cracks is over a relatively fresh slab that's not done settling, especially if you don't use the protective underlayment.

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cybertruckboat t1_iybv68z wrote

That looks pretty normal. It's only a problem if they are growing.

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KRed75 t1_iybx21q wrote

Replying to Helgafjell4Me (#795,447)

You can only try to mitigate cracking using schluter ditra. I've had to warranty cracked tiles laid over schluter ditra on numerous occasions. We no longer install any tiles over a concrete substrate even with ditra.

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Danny141035 t1_iybyac3 wrote

There’s a saying in construction. There are two types of concrete, concrete that is cracked, and concrete that is going to crack. This is nothing

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Spinaccio t1_iycp9yj wrote

I’m more concerned with the unprotected cable coming out of the floor. I don’t know where you are, but that can’t be up to code. Im not an electrician, but I would get one to look at that, and shut off the breaker in the meantime.

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Sometimes_Stutters t1_iycvqx2 wrote

You will definitely want to contact a structural engineer to evaluate this. I have to warn you though; this is very serious so be prepared to do a whole slab replacement of the house.

(I’m joking it’s fine)

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garry4321 t1_iyd2f3s wrote

I worked in new builds, and you would be surprised how much cracking is considered normal. One year in, and crack that goes up halfway up the apartment? Eh, just building settling, put some filler on the crack and go about your day.

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MisterIntentionality t1_iyd2o5w wrote

You will never find a concrete slab that doesn't have cracks.

The problem is when they get large and have height differences.

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PaulClarkLoadletter t1_iyd3ps3 wrote

Cracks are of no concern unless they’re wide or one half is lifting.

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trouzy t1_iydcris wrote

Not even a little

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Gridguy2020 t1_iydirll wrote

Can your pinky fit into it? If not, probably fine.

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Senggerinqin t1_iydl1s3 wrote

Would it be ok to install hardwood floors over this type of cracked concrete slab? I'd assume that the hardwood slats would allow for some movement in the slab without too much unevenness showing at the surface of the wood surface.

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sfdragonboy t1_iydnit5 wrote

Cracks in concrete are fairly common as the earth may settle underneath the slab. I suppose if it concerns you, maybe do have it checked out if a major issue or just a repairable one.

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rightstatewrongcity t1_iydpnai wrote

A structural engineer I know always says “There are two types of concrete Cracked and cracking. “ I doubt this helps.

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MpVpRb t1_iydqe3h wrote

The crack is fine. The wire is not

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boot2skull t1_iyduuqc wrote

Can you see the upside down through the crack? If not, you’re good.

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Helgafjell4Me t1_iye2plb wrote

Replying to KRed75 (#795,869)

I'm curious what types of flooring you do use over slab then? I did tile over ditra in my master bath, there weren't any cracks in the slab, so I'm not worried about it cracking in there, did it mostly for waterproofing and a tiny bit of thermal insulation. I do still have about 1200 sft of slab floor that will need to be redone in my kitchen/dining/laundry/living area. I know I don't want to tile all of it, maybe none of it, but the best I can come up with is luxury vinyl planks (it needs to be waterproof, not just water resistant). Problem is the floor needs to be relatively flat and I can't use any underlayment with that stuff apparently. I'm confused why LVP doesn't allow underlayment when laminate planks do. I could just do LVP in the kitchen area and stick with carpet in the living area, but really would like to ditch the carpet. Large area over a likely unlevel and cracked slab is a problem though. I'm surprise there doesn't seem to be better options.

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