Hi,

I am adding a shower to an already existing tube in a bathroom. I have removed everything down to the studs around the tube and am ready to put up my 4 mil polyethyline sheeting for a moisture/vapor barrier. I know that I need to put up 1/2 inch cement backer board next (following the vapor barrier). I also know that the vapor sheeting overlaps my tub and will extend out from under the backer board.

My question is: at what point do I trim the vapor barrier and how short or long do I leave it? Thanks
Shelley

You can cut it flush with the bottom of the backer board.