I know the cement board is supposed to be cut 1/4 inch above the rub flange, but what if you install the cement board and there is a big enough gap between the tub and the wall that when installing tile, the tile still would not be even with the tub flange let alone go over the flange? After installing the cement board, there is still about a .5 inch gap from the wall to the tub. I assume you can install tile and then caulk along the small gap from the tub flange to the tile. But let me know your thoughts.
you build out the framing with strips of lumber sized to make the opening fit the tub
Youve got the right idea. It's called sanded caulk and it should be available in a color that matches your grout. Just be sure the bottom of your backer board is inside the lip of the tub and 1/4 above it so it won't wik moisture. As far as the why, it's mainly cosmetic. Good luck
Sounds like you should have furred out you framing before installing the cement board. Short of removing the cement board you could add another layer.
It won't look right doing it your way. You need to add another layer of cement board or take cement board off and fur framing out 1/2 . Watch out if this is on wall with tub faucets as your trim ring for valves may be out too far after you add 1/2. Do all sides so they match.
Dude, I don't think you understand anything about the job you are doing. From what you are saying (unless you aren't explaining it very well) you are messing up from the get go. The tub flange should be right up tight against the studs and attached snugly, but not tight, if there are pre drilled holes in the flange. Flat head screws (drywall screws) work best. It only needs attached to a couple of studs, not every one. If there are no holes pre drilled in the flange, don't worry about attaching it. If there is some reason that the tub flange can't go right up tight to the studs, fur the studs out. Do this all the way from the top of the studs to the bottom and make sure they are plumb. Now the cement backer board DOES NOT get cut 1/4 above the flange. The backer board should overlap the flange and be 1/4 above the top surface of the tub. To achieve this, you simply cut some shims out of 1/4 plywood and lay them flat on the top edge of the tub, then place the backer board on top of that. Start your backer board from the bottom (top edge of tub). Then after all backer board is up smooth out joints with mastic or equivalent and caulk the gap between the bottom edge of the backer board and the top of the tub with good silicone caulk. Make sure the caulk is in the gap and not gobbing out onto the tub surface or the backer board surface. Now you are ready for tile.
