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

Flickit

...the Plumbing section.

sepmayr

Hi Peter:
The tub and the tile will expand and contract at different rates as temperature changes; thus (you are right), you shound leave a 1/8 to 3/16 gap, make sure it is dry and dust free after grouting the rest of the tile, and install a 100% silicone seal. tip: 100% silicone will provide the best and longest lasting seal, is, however, difficult to clean. cut the nozzle of the caulk tube in a 45 degree angle, slightly larger than your gap; try to apply a consistant bead, and, prior to using a finger to press it into the gap, spray it with windex or other soap solution. the silicone will not stick to soap, thus allowing you to run a finger (spray it, too!) along the seal, creating a nice cove without messing up the surrounding areas. Then you can simply sponge off the excess.
josef