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Unread 07-28-2013, 09:33 PM   #15
Overthinkin' wife of a caveman
Join Date: May 2013
Location: Charlotte
Posts: 179
Originally Posted by Bubba
paint-on waterproofing is done after the seams are taped, mudded (with thinset), and dried properly. Do realize 2 coats of the appropriate thickness are required by the manufacturer to make it waterproof to their intended level of performance.
Hey, Ron. If your contractor had put poly behind the cbu (overlapping the tub flange), then he could have taped the seams while installing the tile, but, since he didn't, he will have to waterproof the surface of the cbu. You have chosen a liquid-applied product for this. Therefore, he will have to prepare the seams first, like Bubba described.

*I hope a pro will further address the front sides of Ron's tub (tub legs) where there is no cbu. I don't think that important issue has been resolved. I wouldn't know what specific instructions to give the contractor to resolve it, short of explaining the problem and telling him to fix it.

Why do so many contractors think cbus alone provide a leak-proof shower? I've read many threads where the homeowner was told this.

From listening to the pros here, my understanding is that while cbus are immune themselves to damage from water, they can allow water to pass through to your structure. Same with thinset and grout. Therefore, cbus, thinset and grout are not waterproof, and an additional water capturing/routing material is absolutely required, i.e. poly behind OR a surface-applied liquid or fabric membrane.

Good Luck, Ron. I'm glad you're here
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