There are high strength very sticky mortars that can adhere almost any size tile to the ceiling. It isn't an issue, with the right materials. So, that's a red flag. What else is he telling you about a steam shower? Is he discussing the need for vapor proofing? For vapor proof light fixtures? FOr the sloped ceiling? The glass with operable transom? What is missing about how he builds a 25K steam shower, vs the industry standard build?

@strawberry patch designs What is vapor proofing? I know I will need a water proof recess lighting inside my steam shower. Slope, I told him I need it sloped, he said he can do that. The glass transom I also mentioned that to him that it will be needed. Is there anything extra special about waterproofing in the walls? He did say the entire bathroom will be waterproofed within the walls, of course, but I am wondering if there is anything extra that should be done for inside the steam shower unit as proofing. Are there any standard things I should know about before this gets built?

We had 24x48 tikes on our ceiling our tile guy did his research and found that, done correctly, it was safe It was a lot of work, but it looks great and seems very secure

You need someone who knows how to build a steam shower, completely different process than an ordinary shower. And you should not be telling or suggesting to the installer that he needs to do anything, he should know exactly what he needs to do before he took the project.

Thanks for all that info LOMO, and everyone else who responded, it was VERY helpful. Now I am a bit concern with how its going to get built. It seems like my contractor can build bathrooms, tiles and showers but haven’t done a steam shower before. You’ve shared more info than I realized needed to build that steam shower. Of course I want to make sure it is done right.

Now I am having second thoughts about building one, it seems like its a lot more prep work within the walls than I have imagined. And whether or not its even worth building one in my bathroom after all. Sigh.

I do also want to mention that I live in California, perhaps maybe that might be a regulation in my state to not have large tiles on ceilings because we have earthquakes here in my state.

@Sue430 which state do u live in?

Michigan, so no earthquakes! Btw, if it helps, for us the steam shower is worth the trouble. We use it in the winter to heat up the shower before getting in the shower, take an ocasional steam, and with a few drops of eucalyptus oil, its great ror clearing a stuffy head

Is waterproofing and vapor proofing two different thing? Do you need to waterproof and THEN vapor proof for steam showers? Or it just needs to be "vapor" proof instead of "waterproof"? Trying to understand all these terms.

" Is waterproofing and vapor proofing two different thing? "

Absolutely different. Vapor proofing is a heavier material and will also make the steamer waterproof. You do not need or want both.

Mosaic is not a requirement for a steam shower ceiling, or for any shower ceiling. Your installer telling you you need mosaic shows me two things. 1) Your installer is not comfortable installing larger tiles on ceilings. Could be that he's aware of his own limitations? Or that he likes taking the easy way when it comes to most jobs? Or that he doesn't know about better performing thinsets? Or that he just likes to do things his way? 2) He's never built a steam shower before. With mosaic on the ceiling, all those additional grout lines are going to result in condensate dripping down on the person using the steam shower. Not a nice sensation when trying to take a steam.

None of that means you installer is incompetent. He may be willing to learn, he may be willing to go the extra mile, he may do fabulous work with amazing detail. Or he may be in over his head.

Have a good conversation with him about what needs to be done for a successful build, and gauge his response. He may be the old dog who is willing to learn new tricks with and along side you, or he may push back with the "I've always done things this way".

Find out what material is going to be used for the vapor proofing and then research it to make sure it is indeed vapor proof.

Some tile backer boards have vapor proof membranes are already applied to foam board. Two birds, one stone, you get insulative value plus vapor proofing. Some membranes are a manufactured sheet that get thinsetted to a backer board. You know the membrane has the required perm rating, the seams just need to be properly detailed. Then you have liquid applied membranes. They need to be properly applied to get the vapor barrier performance. They seldom are. They are typically slapped up on the backer board quickly, creating air bubbles and pinholes that never get taken care of with additional coats. Reinforcing fabric sometimes gets used where needed, sometimes it doesn't. The more detailing and care the installer has to do to get a good installation, the more chance you're not going to get a god installation. ESPECIALLY with someone who has never done a steam shower before.

Most people think a steam shower is simply a regular shower with a steam generator added into the mix. Nope.

You've gotten some good info already; resources as well as explanations.

A steam shower simply requires the correct materials used within as well as attention to detail when being built.

You'll want some form of insulation on the wall to improve the performance of the space. You'll want a true surface applied vapor barrier to prevent moisture drive into the tile backer board. You'll want to consider porcelain tile, tile with a low water absorbancy. Porcelain is a better choice over the other extreme, handmade tiles that look terrific but are porous as heck and will hold moisture.

Good luck with your build, I hope you get a satisfactory outcome.