drywall

Replacing shower and decided to redo bathroom flooring at same time. Got the tile up and there is something that appears to be thin Gypsum or drywall (1/4 in.) Is this normal? Just a different underlayment? I only ask because the previous owner tried flipping this house and messed up several...

I stupidly framed out my basement and put up drywall, which looks great. I then realized that I should level the floor - it drops 3-4" over 12' and it isn't flat, either. I want to use concrete to level the floor so that I have more flooring options. My drywall ends ~1" off of the floor so that...