Jadnashua
Retired Defense Industry Engineer xxx
My guess is that that stuff has in the fine print not suitable for wet areas. If they recommended it, they should fess up to their ignorance and pay up. Probably not worth it, but a complaint to the better business bureau might enlighten them a bit and save the next guy. Just verify first! No pro worth his license would use mastic in a shower, nor does the TCA approve it.