How to Waterproof a Bathtub?
During your shower tile installation, be sure you water proof your shower. You can accomplish it by stapling a visqueen barrier directly onto the studs underneath the cement backer board. As an additional safety net to waterproof a shower, you can also add DAP Silicone Max over the screws on the backer board.
Why do you use cement backer board when doing shower tile installation?
When installing tile, you need a backer that is going to accept the thinset mortar, which is how your tile will adhere to the wall.