I am a high-end contractor and have unfortunately installed cement tiles on a number of projects this past year. My installers followed supplier recommendations and on later projects (when we started noticing staining on earlier projects), applied several more coats than recommended. All the floors are covered with stains and my clients feel like they can't relax, as any drop of water needs to be dried immediately or a new stain will be left. I've spent many hours now on my hands and knees sanding out stains, trying new sealers, etc. I'm honestly now exploring options for pouring epoxy over the floors to allow my clients to live on them. I will NEVER AGAIN install cement tiles on a floor (or anywhere that could get exposure to water or any other liquid).

I spoke to one of the workers today and told him it was industry standard to use this plastic. I don't know anything about curbs or mud, or any of those other words. I asked him about this book, and of course, he looked at me like I was crazy. My husband spoke to the contractor who said this is totally unnecessary, and that he has been doing this for years this way, even in his own house. -- I told him .- this puts me in a weird predicament because I don't want the job to be done wrong, and I'm not convinced that this is right. We are at a stand-still. I want to take a hammer to those tiles-- I am waiting to hear from the store-owner who sold me the tiles and ask her advice about what I can do now..... I am also going to ask her about the glass shower tiles with cold and hot water. This is why I hired a Contractor -- I don't want to make all these calls and teach myself how to install a bathroom, or a floor, or a fireplace! Creative - I cannot thank you enough. I looked through the book you are referring to. The contractor thinks I'm reading into everything because this isn't the first thing I've complained about.... This is the text he sent me this morning "The vinyl on floor and up walls about a foot and up seat area and on wall behind you do not need on walls unless steam shower nobody puts on wall you are reading to much No concern my own shower is done like this"

cement tile isn’t expected to look perfect. Part of the charm is for it to patina over time. I’d just seal it with a matte finish seal. Do at least 4 coats. A gloss finish would be odd on a cement tile IMO. The contractor should be offering to replace the tiles and do it properly. Cement tile should be sealed before and after install.

It will be hard to speculate based on your picture. If you want some tile experts to chime in, take and post a better picture. I'm NOT a tile expert (I do wood) but I've seen plenty of efflorescence. It's not something that generally happens right away so I'd wager that the issue is something else. From wiki: "In chemistry, efflorescence is the migration of a salt to the surface of a porous material, where it forms a coating". It stands to reason that migration of salt to the surface takes a bit of time. I usually see it on older floors. It takes time to manifest.