I have a cultured marble shower base without the usual 3/8" lip along the edges; it's just a flat surface. All of the information I've found so far for transitioning between the backer board and shower pan with a tile wall include the lip in the diagram. I'm wondering without the lip should the concrete backer board and tile be place directly on the shower pan edge?

Thanks,
Paul

Any chance of a picture or brand name? That lip provides protection from water getting behind the wall, never seen a shower base without it, yet.

When folks want to install a drop in tub as a recessed install with a shower head, a tile bead kit is used. It's a flexible rubber gasket that gets installed using a supplied self adhesive tack along the outside edges and has a thin leg that extends onto the deck of the tub and creates about a 1" high flange. A bead of sealant is used where the leg extends over the tub deck. I think that would be the safest option with your shower pan. Once the flange is installed, drape 4 mil poly sheeting over your studs and let it overlap the flange. Install your cement board so that it stops 1/8" above the top of the flange. Unless you planned on using small mosaics on your walls, your tile will ride over the gap between the cbu and the shower pan deck, no problem.

Thanks much for this help.

For a picture follow this link (although mine is cultured not real).
Shower trays shower pan stone sinks marble granite bathroom China limestone travertine (http://www.ghystone.com/stone/carving/stone-sinks-marble/shower-trays.htm)

The tile bead kit sounds like it would do the trick, I'll dig into that further.

Thanks,
Paul