foundationtips.com In this video you can see where we filled in the concrete flooring that we removed, after we installed our new waste pipes for our toilet, sink, shower and bathtub. It took about 25 bags of 60 pound concrete mix to fill and repair the new bathroom floor. I added additional cement to the concrete mix to give it more strength. Make sure that you dowel into the existing concrete floor slab to avoid some of the problems you could have in the future. The dowels prevent the concrete from moving up and down, creating problems with your flooring. Check out some more of our bathroom remodeling videos, for more helpful tips and advice.