How long after pouring a thin layer of concrete (sand topping between .5 - 2" depth) should I wait before leveling with self-leveling compound?

I'm mostly concerned that it should be done shrinking/altering shape more than it reaching some sort of maximum strength. This is an interior floor where I'm adding more concrete on top of an existing slab so it's going on a solid base and not supporting weights like cars.

Background: I have a large room with concrete floor that had a lot of low spots. I'm pouring concrete where the dips are deep enough then will finish with SLC. My concrete skills are too weak to just do concrete well enough for me to trust not needing to then level. It's excess work, but saving thousands vs. doing just SLC.

  • I have to wonder if you'd save thousands and get it done in one go by hiring people with better concrete skills (and tools and experience.)
    – Ecnerwal
    Commented Sep 15, 2020 at 1:34
  • Initial research was telling me $4K - $6K more, but I'm kind of late in the game to go back ;) Plus I'm a bit of a glutton. Commented Sep 15, 2020 at 1:38
  • I just don't get why you wouldn't have poured to "level" in one go. This if for sure a bad idea for anyone in the future.
    – DMoore
    Commented Sep 15, 2020 at 4:04
  • @DMoore SLC is 5-7 times as costly. Commented Sep 16, 2020 at 1:28

1 Answer 1


You still need to follow the instructions for the SLC - most (IIRC) say 30 days minimum cure (for the underlying concrete.)

Be sure to keep it damp so it can actually cure. If it dries out, it stops curing, and that's a very likely thing with a thin pour over an existing slab that will want to suck water out of it.

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