I feel kinda of dumb with this question. I am tiling the wall around my bathtub and there is a 5/8" green sheet rock and I want to put 1/2" backerboard on top of that and then the tile. All of this will over lap the bathtub lip. Will cualking the gap between the tiled wall and the tub work. I have never done tile work before and would like to do this project.

thanks for any advice.