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Concrete Slab Repair - Second Floor Bathroom

Renee Kraft
7 years ago

Hello! We are remodeling a second floor bathroom. As we suspected, when we removed the floor tiles, we found a concrete subfloor that is several inches thick.

We've been debating between removing the slab and repairing it. I think we're just going to repair - mainly because of the cast iron tub we don't want to disturb and also because we're pretty sure the toilet flange would be too high and we don't want to mess with that. Based on the wood subfloor height and the tub height, I think we'd end up with a decent step-up into the bathroom regardless of approach. So, while I'd like the floors to be perfectly level, that doesn't seem to be in the cards.

The tile came off pretty easily and most of the floor is in excellent shape. There are, however, three areas that need to be repaired. One is in the middle of the floor - my husband got a little overzealous in his tile removal and made a 2-4" wide divot in the middle of the floor that's about 1-2" deep. I'm guessing this can be patched with some good thinset. The other areas, however, go all the way down to the wood subfloor beneath. We repaired/replaced some of the plumbing, which caused the holes. In both cases you can see down to the first floor below (wood subfloor is cut through in a couple of places). Is there any trick to patching these holes without too much cement falling through to the first floor? My thought was to lay down wire mesh and pour in thinset, but I'm worried gravity will be working against me here. Are there other tricks or steps I'm missing?

Thanks in advance for your input!

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