: : I am building a custom shower that
: : is on an 8" concrete slab. Is it
: : necessary to install a membrane
: : or can I just create the slope I need
: : to the drain and just tile over the
: : the concrete slab?

: If this concrete is not cracked and is 8" thick and well cured i would think a good coat of water proof adheasive should be ok.But being a pesimistic fellow i would put a corelon layer on first. Please excuse the spelling. Dale's Plumbing Service LMP

I too would line the shower area.
At some point, the tile grout is going to have a little leak and
your concrete slab will be damp for many inches or even feet around your shower.

Good health, Weogo Reed