debi, here's the thing: True cement board is made of non-organic "ingredients". Nothing cellulose-based, like the paper facing on gypsum board. Cement board will not degrade when undergoing long periods of water saturation. It will not degrade after repeated wetting and drying cycles like the gypsum core in gypsum board. So does cement board itself have moisture protection and mold resistance? Yes. Because there's nothing organic in it to feed mold, and there's nothing in it that will degrade from water exposure. But you'll note that it does not say cement board is waterproof. It's not. Water can wick right through it. And what's on the other side of the cement board? Your house's wood framing. Again, you'll find manufacturers telling you about their specific product, but they can't say how their product will interact with or protect materials attached to it. So cement board is essentially not affected by moisture. Your house's wood framing will be affected by moisture. Insulation can be affected by moisture. So you have to decide how to prevent moisture generated by your shower from reaching the wood framing or any insulation within the framing bays. Obviously the tile and grout will shed most of the water. But that's why a barrier of some sort needs to be included before residual moisture and moisture vapor driven through the assemble can reach the wood framing. There are a lot of people who build incorrectly. Some through ignorance, some through apathy. Two dollars worth of 6-mil plastic could have solved this before the cement board was installed. You can unscrew the cement board, hang the poly and reinstall the cement board. Or leave the cement board up, mesh tape and mud the seams, then use a topical membrane to waterproof the CBU. Based on the path this thread has taken, I'll toss this out. When you tile, don't use mastic. Don't use any premixed comes-in-a-tub type of adhesive.

I saw one about 5 years ago in a specialty bath showroom in Portland. If I remember correctly it was close to $5k. I'm guessing at that price they didn't stick around. It was a slipper tub with what I thought was a Perrin & Rowe exposed pipe shower attached to a glass enclosure that was framed in rounded metal pipe. I would love to see one as well - boy were they gorgeous! Perhaps if you inquired at a specialty bath shop some of the old timers might remember one?

It sounds like a simple tub and caulk problem, not really an issue with the Kerdi. Do you recall if the tub's flange was fastened to the wall studs? Normally a nail goes through the flange into each wall stud. That'll prevent some vertical movement/deflection at the flange. I can't say if adding under-support will help at this time. If you hear squeaking and creaking when you're in the tub, that could be a sign of movement. Do you see any movement at the flange when the tub is loaded and unloaded (water, bathers, etc)? Or do you think that the original caulk failed simply due to a one-time "after installation shift" and that the tub is now settled in place? I'd pull the existing caulk. Clean, let dry. Load the tub. Then install silicon. As far as the mold returning, realize that bleach will only kill the surface mold, but not the mold's "roots", so the mold can grow back since it was never killed in the first place. Household bleach is about 6% "bleach" and 94% water. When put on grout or wood, due to its polarity the bleach stays on the surface of the material. It doesn't penetrate into the material. Only the water penetrates. So when you bleach a porous material, you are indeed killing the surface mold, but the water is feeding the mold's roots. Not a truly technical description of what happens. But that's why bleach itself isn't an approved "mold killer".

Thanks, Errant. I always check Amazon reviews, but there weren't any for this model when I bought in 2006. I'm really, really kicking myself for buying something expensive and pretty, but that doesn't do the most basic of what it is designed to do. Plus I had a good opinion of Kohler, so it's really disappointing that the company is not standing behind this product. Thanks, enduring. I don't think so -- it appears to be a different style drain assembly.