As with any other gap near your bathtub you ll want to close the opening to prevent any possible water damage or the onset of mold and mildew.
Transition from wall tile to bathtub lip.
Apply it to the wall with the bottom edge about 1 4 in.
Above the lip of the tub.
The best approach when installing cement board or other tile backer around a tub is to keep the cement board out of the lip area.
This issue is sitting there for a long time now and really bother me.
I checked the tile grout.
Then apply a generous amount of thin set to the bottom bathtub tile and position it 1 8 in.
The tub is designed to sit on the floor and be screwed to the studs kohler recommends setting in mortar which i did.
This video will show you how to set tile around a tub.
This kohler acrylic tub is thick the flange is more than a 1 2 thick if you run the cement board over the flange and the tile which is about 1 2 thick when thinsetted it will come too far into the tub.
This gap may widen over time as your home shifts.