This is a mostly unfinished basement with the exception of this bathroom (on the other side of this wall). The builder finished the bathroom. If you look under the tub, there is no concrete floor, it’s gravel. Which would be fine if it were a crawl space but it’s not. Even if it were a crawl space it would have a vapor barrier.
So is this an issue, having a big hole in your basement floor? It will be walled in soon but I feel like there should be some kind of barrier there.
Good catch. In my area, moisture coming up from the floor will cause bigger issues than one may think. You don’t see the hole in the slab in the photo, but this growth is adjacent to an unseal plumbing cut-out in the basement floor.
no contractor will pour concrete around the TUB P-trap. its a small square hole filled with gravel to still have access to the trap if it was to ever clog. it will look exactly the same if the concrete was a wood subfloor. Look up tub install instructions.
They could have sealed it with some plastic, but its typical and correct.
and by the way Radon can travel through concrete just as easy as gravel.
Concrete cures by reacting with water – hydration. But almost half of the water added to the concrete mix for workability is surplus and has to evaporate. As the surplus water in newly poured concrete pushes to the surface, it leaves behind a [network of capillaries (pores).
The pores constitute 12 to 18% of the concrete by volume. Their diameter is much smaller than a single human hair but the pores are much larger than radon atoms or water molecules. They let in soil gas carrying radon and water vapor.
The dominant transport mechanism by which radon gas moves through an intact concrete slab is concentration-driven diffusion. Studies have shown that indoor radon entry rates can be greatly affected by the type of concrete mix employed.