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Floor drains and mosaics on curbs
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Ask the Experts Q&As are culled from member inquiries to NTCA’s Technical Support staff. To become a member and make use of personal, targeted answers from Technical Support staff to your installation questions, contact Jim Olson.
QUESTION The plumber installed the foam pan and flange before we arrived on this job. The drain flange has too much mortar and the slope is off. From front left corner there is only 1/4" slope to drain in 2'. With a flat stone mosaic, we will need all the slope we can get. Would it be possible to float over this pan? Do we need to pull the flange and then float it to a new flange? Just wondering what would be best practice.

ANSWER In short, the onus is on the plumber to have installed it correctly to begin with. My suggestion is to inform them of the issues and advise them you cannot accept their installation. – NTCA Technical Team
RESPONSE Thanks for the feedback. We have been in touch with CTEF’s Scott Carothers, NTCA’s Robb Roderick and our manufacturer rep, and the final call is to tear the whole thing out and start from scratch. The manufacturer was not comfortable giving a warranty with so many variables in play. Thanks again to all of you. It makes our job much easier.
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QUESTION Would this mosaic be advised over a curb? It will be installed on shower floor, up over curb to the bathroom floor. It is 3/16" thick. Glass doors will be installed on top of it. ANSWER Is that a foam curb? If so, consult the manufacturer of the foam material to determine the minimum size of tile that can be set on/supported by that material in a horizontal, weight-bearing application. As far as the tile’s ability to support weight/load, I see no problem with that as long as you have a very sound substrate and full bond coat support of the tile. I have personally installed similar tile in bathrooms where extremely heavy cast iron clawfoot tubs were set on top of this tile after I installed it. A shower has an environmental exposure classification of 3, which is described as “frequently soaked or saturated.” This affects the methods and materials you use for this installation. The manufacturer of the tile can tell you if the tile is suitable for use in a shower. It’s hard to be certain from a picture but it appears to be a ceramic tile that most manufacturers would allow in a shower installation.  Was your question about laying out the tile on a curb? If so, you should research a couple options for finishing the curb corners. Some mosaic manufacturers make a trim piece that can be used on the corners of the curb. Designers sometimes use accent pieces or metal end tops for the curb corners as well. – NTCA Technical Team