I doubt he knows what he's doing. Kerdi over either cement board or drywall is the route you need to take. Floor, walls and ceiling. Nothing else will do. Some folks like a sloped ceiling at 1/2" per foot. Others say that sloped isn't really necessary as it isn't a "commercial" shower. Personally, I don't think you need the slope for a residential shower....but, that's just me.

He said he has installed a few steam showers. He mentioned the ceiling slope and ventilation options, but I'm not sure about the vapor proofing. It is hard for me to question him when I do not know how to do it myself.

What are the acceptable options for vapor proofing a steam shower (other than Kerdi)?

To educate yourself, I suggest you Google something like "how to waterproof a steam shower." When I entered that, one of the FIRST things I read was not to use tar paper but to use a product like Kerdi, Laticrete, Noble, etc. and there are knock offs of these products as well. Even if he does what he says, from what I understand, there should still be a water proofing membrane under the tile. There are even YouTube videoes of the process, and, of course, plenty of information here in the archives - easier to access through Google than through the search feature here.

There is a really good online forum for tiling but the system won't let me post it - initials JB

Hi, Bill, yes, it is California -- how did you know? I would be very relieved if he does have it right. I don't want to harm the relationship by questioning his expertise if what he is planning is ok. What he was describing just sounded very different than what I have read here and elsewhere online about steam showers.

How does a CA mudset steam shower differ from other steam showers? Is the craft paper membrane a vapor barrier?

A lot of tile guys in California do what Bill would call an old-fashioned mud job. That's how the steam shower was build in my previous house, and this is what my current steam shower looks like - it has about 6 inches of water in it at the moment. The hot mop guy was so proud of his work that he left his card on the curb ;-)

Forgot to mention that our local code requires green board and a sloped ceiling of a half inch per foot.

Three things you can usually count on;

-Hot mopped pans mean California
-Copper pans are Massachusetts
-Lead pans are NY

Mongo got it. The hotmop was the give away. As for the ceiling code, that SHOULD be 2" per foot. The ceiling slope in a steam shower is supposed to be extreme, so that condensation doesn't collect and drip cold water on the occupant. Nothing says it has to slope all in one direction, like this pic of salbwil's shower:

It can pitch in two directions, like the pitch of a roof-- like this:

Or, it can even slope in 4 directions:

Thank you all. I am relieved to know that an "old fashioned mud job" (which we've had in our last 2 non-steam showers) is okay for a steam shower. With all the other issues we've had with this house, I don't want to be at risk for mold too due to a faulty steam shower install.

Bill, thanks for the ceiling pictures -- nice to know we have options. Annkathryn, it's good to know your hot mop guy was proud of his work, lol. I hope you will be enjoying your new steam shower soon.

Good "catch" on the Cali deal, Bill. You are, of course correct. The mention of greenboard kinda threw me off.