Uneven floor

Ok guys im remodeling an old house like 90 years old in the bathrooms im putting tile and the floors are uneven it has a wood subfloor and im putting backerboard down first but from the door to the other end of the room it drops an inch can I just put sand down and level to make up the low spots then put my backer board down to lay my tile or do I have to try useing some kind of self leveling cement?

Hello there, the best for your unlevel floor is to use MUD, this way the floor will be even, this is the old fashion of doing tiles, I personally use MUD no matter what,that's what my customers want. Good luck