Snag wrote:
.."

http://www.custombuildingproducts.com/products/surface-preparation/membranes-underlayments/redgard.aspx

Video:

http://www.youtube.com/watch?v=mG5GIqcYkSs#t=24

Interesting stuff , but not applicable in my case . I'm on a
suspended wood floor , and will be using a two-part shower drain flange with a
vinyl pan . Floor will be 4:1 sand/cement dampened enough to pack and bond
then tiled . Walls will be concrete backer board on the bottom 3 feet ,
green board sheetrock above .

My last project I used HardiBacker all the way to the ceiling and redgarded
that. I will NEVER use greenboard in a shower again. That was why I was re-doing
the shower.