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Discussion Starter · #1 ·
We are remodeling our shower, and have questions about waterproofing:

1. I have seen videos where people are putting the paintable waterproof membrane over their entire finished cement pan, even though there is a PVC liner under the pan. I was planning on doing this as well until I read online that this would create a "mold sandwich". We have a pre-slope. Would it be fine to paint the membrane on the walls (which are cement board) and down to the pan, covering the pan about 5 inches or so around the outside perimeter? That way if water seeps down into the cement that doesn't have the membrane, it can make its way to the weep holes. What do you recommend?

2. Also, in setting the cement board on the walls, I have seen several videos where they say not to let the bottom of the cement board touch the pan, and to leave a 1" gap from the bottom of the cement board. Then to tile the floor, pushing the tile underneath the gap. After grouting, there will be about a 1/2" gap left at the bottom. Do you advise doing this? We have already completed our pan, underneath that is the liner and under that is the pre-slope. In some videos on youtube, they say to use a paintbrush and apply the waterproof membrane inside of the gap first, then to install your wall tile down to the floor tile. But doing it this way there will still be a gap behind the bottom of the wall tile. Should I apply caulk to this gap before tiling? Or should fabric be applied first, then the liquid waterproof membrane? Or should I put the cement board all the way down and have it touch the pan?
 

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Are they recommending leaving a 1/2" gap between floor tile and wall tile???

If you're tiling your pan, I would say to not even put up your wall board until that's done, so you know exactly how high your tile is. Then I would put the wall tile in with the same gap to the floor as between the tiles. No grout at the floor-wall joint, only caulk.
 

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Discussion Starter · #3 ·
I actually went ahead and installed the wall board down to 1/8 of an inch to the final mud pan, per someone's suggestion on another forum. the main question I now have is should I fill the gap with thinset, and then use a waterproof membrane fabric with the liquid membrane over top to cover the gap from the bottom of the cement board to the top of the mud pan?
 
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