tile installation around tub

I am about to install a new tub in my daughters house. She has already gutted the bathroom so I have a clean slate. She wants the walls done in ceramic tile in the tub/shower enclosure. I plan to put up a membrane under the cement board. My question is, where do you end the bottom of the membrane. I would think it should overlap the top lip on the tub but I'm not sure. I've always heard that you should leave a small space between the tub and the bottom of the cement board to prevent any water from wicking into the board.Pros-cons??
--
"shut up and keep diggen"
Jerry
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.