this post was submitted on 28 Aug 2025
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After a bad water infiltration issue, I started investigating around the main problem area in our machine room. There was what appeared to be a long surface crack which ended up being a diagonal crack right through the 6" slab. It extends under a wall on top of which (I believe) rests our staircase.

My idea was to temporarily cut the bottom plate so I could open the crack (concrete saw and/or jackhammer) and pour new concrete, but there's a stud right on top of the crack. Any ideas how to best approach this?

EDIT FOR CONTEXT: Foundation was piered/piled 6 years ago. This was the corner that had dropped the most. It's not moving anymore. The company doind the work told us the crack was superficial and they weren't worried about it... 😮‍💨

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[–] AmazingAwesomator@lemmy.world 9 points 12 hours ago

do not do what i would do.

rug.

[–] vk6flab@lemmy.radio 12 points 13 hours ago

If it were my problem to fix I'd ask an independent building inspector since the company who built it is unlikely to tell you that they fucked up.

Under no circumstances would I touch any of this myself until a qualified independent professional had fully documented the situation.

Consider what the impact is if you repair something incorrectly and it all comes falling down.

[–] Brkdncr@lemmy.world 6 points 15 hours ago (1 children)

If it’s not moving then I wouldn’t worry about it too much. But it looks pretty big.

Cut a line perpendicular to the crack and drop rebar into it. Do this every foot or so, or whatever makes sense. Widen any small cracks so you can fill them.

Fill with concrete that’s designed to stick to existing concrete. This should tie the crack together so it doesn’t move more.

Mud jack ahead of time if you need to level it out.

Simply filling with concrete or epoxy won’t do anything except reduce water intrusion until it widens again.

[–] ikidd@lemmy.world 1 points 9 hours ago

Epoxy is more typical when you're trying to anchor support into existing concrete.

[–] ObsceneGondolier@sh.itjust.works 5 points 17 hours ago (1 children)

Had an issue posting the photos, here we go:

[–] ikidd@lemmy.world 2 points 9 hours ago

I'd drill some rebar into the sides and anchor with epoxy (blow the holes out well) and wash the exposed faces down and let dry. Paint with the shit you use to prep existing concrete for adherence, then pour quickcrete with some adhesion compound added. If it's not moving anymore, it'll be fine for years.

[–] redlemace@lemmy.world 4 points 17 hours ago* (last edited 17 hours ago)

My 5 cents ... I think the wood can bare the load, but you can add extra vertical posts above the concrete.

As for the crack, I'd consider cutting a V shape accross the crack (3" deep). Make it dust free, lay 10mm steel rods in them and fill it all up with concrete. (The idea is it will help preventing this crack from widening)

(But I'm not a pro! Do also get advise from someone that came on-site and not just asses photo's on lemmy)

[–] yaroto98@lemmy.world 3 points 16 hours ago

Sooooo, from what I understand, a 2x4 is non load bearing. It's framing. You should be just fine taking out a single 2x4 without issue. Especially in a basement. All the load bearing in a basement will be metal pillars or resting on the external concrete walls.

[–] Broken@lemmy.ml 4 points 17 hours ago* (last edited 17 hours ago)

Just a dumb DIYer so take this with a grain of salt. You can put in a stud to the left and right of the stud in question to bear any load. Then after the floor repair is made you can replace the original stud (I'd probably leave the 2 temp studs as well since they are already in place just for overkill support).

You'll want to look into the structural impact of cutting the base plate though. Seems like cutting a section out might require more than just putting it back with some metal straps.

Also, look into epoxy for the concrete fix. I know they have epoxy specifically for injecting into concrete cracks to restore integrity. Seems like it might be much easier (and possibly be able to work around the framing). It'll probably be more expensive, but pay off in convenience.