0

I’ve got multiple large trenches busted up in my 1911 basement floor where new drains were put in. It’s time to fill them back in with concrete but I’m concerned about water coming up through the seam between the old and new pours. Making it harder is that this break was jackhammered, not cut clean. I know there are many threads about hole patching, but I'm specifically concerned about these edges.

How can I make this sealed tight and ensure no water or even light moisture get through? Welcome any good ideas.

enter image description here

enter image description here

Improve this question
2
  • 2
    You can't ensure that no water or light moisture comes through the uncracked slab. You should focus your effort on getting good compaction below the patch. If you have a rotary hammer or get a 100 USD one from Amazon or Harbor Freight, then doweling some #3 bars (3/8") every foot or two along the perimeter of the patch can prevent differential settlement. A vapor barrier below the patch isn't a terrible idea, but if there isn't a barrier elsewhere, then I wouldn't consider it a big deal.
    – popham
    Commented Mar 22 at 5:00
  • As long as the edges of the adjacent slab are flared so that the patch is narrower on the top than on the bottom, the concrete shouldn't "pop out." But there's no way you're gonna seal that against any water intrusion. The only thing you can do is minimize water getting beneath your slab in the first place (various methods).
    – Huesmann
    Commented Mar 22 at 15:40

1 Answer 1

Reset to default
2

If you're concerned about water coming up through your floor, sealing the surface won't really solve your problem. You need to look into perimeter drains of some form to prevent the water underneath your basement floor from even getting to the floor level.

Improve this answer
3
  • The first rule of concrete is that it will eventually crack, somewhere. If it hasn't cracked yet, it will at some point in the future. At that point any sealing you've done previously is no longer going to seal water out, and as many have found out, water pressure from underneath a basement slab is a relentless force, and will eventually get inside no matter what you do.
    – Milwrdfan
    Commented Mar 22 at 15:03
  • 1
    OP here. I followed all the pointers here and need to confirm, now that the project is done that they’re right: water will inevitably find its way through. Thankfully I did the work under the slab to make sure water flowed well to my new sump basin. But as soon as I forgot to plug that sump back in and we had rain, the floor was moist and wet all along the seams. Sump’s now been on for weeks and the floor is bone dry.
    – Jeremy P. Beasley
    Commented May 7 at 6:22
  • 1
    Thanks for the final result report!
    – Milwrdfan
    Commented May 7 at 13:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.