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Unread 12-03-2019, 08:39 PM   #10
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

Join Date: Jul 2004
Location: Nashua, NH
Posts: 13,478
Thinset, tile, and grout are all less than waterproof. Deck mud, OTOH, is pretty porous, so moisture SHOULD pass through it fairly quickly, the others, less so, but still potentially noticeable. How thick was the thinset you used on top of the finished slope prior to adding the thinset and tile at the end?

THat thinset layer could slow the water getting to the weep holes as it's less porous than the deck mud beneath it, potentially holding that moisture longer.

Since marble is a natural substance, the quality and performance issues will vary between not only types, but also from where in the quarry it was mined. Smaller tile like on your pan, could have come from multiple locations, thus, they could respond to being wetted in a different manner.

Sealers don't actually block moisture. They are designed to help slow down the absorption of stuff, giving you a chance to clean it up prior to it sinking in far enough to permanently stain.

Some grouts are more water permeable than others (most epoxy grouts are nearly impermeable). Cement based one, much less so.

Industry standards call for changes of plane and material should have a soft joint. In a shower, that typically is done with caulk. Grout often does not fare well in those locations. The alternative is to use an engineered profile joint, but that adds to the initial costs, and people often don't want that expense (often will end up seeming cheap when the caulk needs to be dug out to refresh, though, maybe many times over the life of the shower!).
Jim DeBruycker
Not a pro, multiple Schluter Workshops (Schluterville and 2013 and 2014 at Schluter Headquarters), Mapei Training 2014, Laticrete Workshop 2014, Custom Building Products Workshop 2015, and Longtime Forum Participant.
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