I am installing new tile on top of a new cultured marble shower pan. I rested the durock on the top lip of the shower pan as directed by company. Its now time to tile the walls. Should I rest the first row of tiles directly on top of the shower pan or should I lift the first row up just a little maybe 1/8 inch and caulk the gap between the shower pan and the first row of tiles or maybe even grout the gap. Thanks Peter