I removed a neobase corner shower down to the studs and have installed Durock. The Durock doesn't extend over the lip of the shower base, I used caulk to fill the 1/4 inch gap per their web page.
My question is how much of a gap should I leave from the base to the bottom of 1st row of tiles and should I caulk or grout this area? There may be some amount of tile (1/2 to 3/4 inch) that is on the Durock but not touching the base about 1/4 inch away. Should I use mastic for fill this hollow area?