Superman, I will answer your question about whether or not cultured marble has the same maintenance issues that marble does. NO, it does not! We had a cultured marble base custom made for our basement bathroom over 4 years ago, and after heavy use for that time, it still looks just like new. I went with a honed finish (not crazy about shiny cultured marble) and a very subtle white on white pattern. we had the walls done too, and an 8" wide shelf that continues on out of the shower the whole length of the room. It is not cheap, I have a quote right now for my master bath, and the 3' by 5' base will be ~$1100 before taxes, not counting delivery and install. I have never regretted our decision, this is our guest bath (but we use it now instead of our present pre-reno master), and guests have commented on it's being the nicest shower that they've ever been in! So, so easy to clean, no discolouration whatsoever, I squeegee the walls after my shower, and every once in a while wipe with Method cleaner and a microfibre cloth. the squeegeeing may be unnecessary, but I'm doing the glass walls anyways, and I figure less water sitting around in the basement bathroom... is a good thing!

Those are really common sense answers that don't really address the actual question... Obviously getting a nice one piece surround would be ideal, or having the entire walls demo'd out and done with fresh tile and proper waterproofing, etc. But can't there be a possibility of a good product to use? Yes absolutely, but what are they is the question. Unfortunately, I don't have a great answer for you either, but I'm looking into it. I'm trying to find something that can go right over the tile too though, for you, just a paint / epoxy might work fine. I want something that can also be flexible enough to span cracks, but your application just going over regular walls down to the tile may not need that exactly. I haven't tried the Zinsser watertite clear but I've been looking into it, which is how I came across this, hoping to find some clues for my own. They have a clear that might work just fine for you, not sure if you used like the white for example and didn't know there was a clear. You would think someone would have a decently abrasion resistant, clear, semi-flexible coating that goes on like paint for tiled showers to seal them and make a million bucks, I'm honestly quite surprised it doesn't seem to specifically exist. For your application just about any marine clear epoxy might work too, followed by a good uv coating since you probably don't have to worry as much about cracks as I do. FlexEase was one I found that looked good. *I realize this is an old question but thought there is a possibility you might still be looking for something, or if you found a good solution, please let me know what your experience was with it.

"My contractor used mastic everywhere he installed new tile for me--kitchen floor, foyer, etc. Is it okay in these areas since they aren't generally wet, or is this still a no no? " Laila, it depends. On your substrate and the size of the tile used. Substrate: Some manufacturers restrict the type of material that you can spread mastic on. Example, many prohibit OSB and chip board types of subfloors or underlayments. Tile size: Mastic cures by drying, so it needs exposure to a certain amount of free air. Some restrict the size of the tile you can install on floors and walls. Floors size is usually more restrictive due to the weight of walking on the tile. If the mastic can't see enough air the mastic can remain soft. One mastic I've used has I a maximum of 6" square tiles on floors and 10" square on walls. Another manufacturer restricts tile to 12". Some prohibit setting natural stone tile on floors with mastic. So within the entire family of mastics, each manufacturer may have their own limitations due to how they formulate their specific products.

Thanks Mongo. I went down to the local tile warehouse and talked to their technical guy. He told me the same thing. He carries Ditra and Laticrete's Strata-Mat as uncoupling membranes and the full line of NobleSeal products. For my one inch hex tile he recommended NobelSeal TS goes down on the floor. Additionally my base won't be just plywood. The tile guy will be putting in a lath and mortar bed to level the floor and provide a solid base. I asked why he doesn't use a cement backer board and he said that he doesn't like the way it follows any variations in the plywood or the joints. He says a mud job gives him a "truer" surface. He is going to install the NobleSeal TS although he remarked that it's probably overkill on my fairly small bathroom with a 1" hex. He normally installs Ditra with larger tiles in bigger bathrooms. He also uses Hydroban on all the surfaces around the tub.