He might be referring to "hydraulic cement". Hydraulic cement expands a bit as it cures, it's often used to seal foundation punch-throughs; holes though foundations for plumbing, electrical, septic, and cracks in foundations, etc. "Would you use Wedi, then Kerdi membrane over it (for the steam)? Or is hydroban also ok in a steam shower? " As a stand-alone product in a steam shower, again, Wedi is not appropriate when used with typical tile setting materials (portland cement based thinset and grout). To make Wedi vaporproof you'll need a vapor barrier. That's why Wedi's instructions specify using epoxy adhesive to set the tile and epoxy grout when using Wedi in a steam shower. The epoxy will be your barrier. If you don't use epoxy then you'll need some other sort of vapor barrier within the wall system. Wedi ($$$$$) plus epoxy adhesive ($$$) plus epoxy grout ($$$) is an expensive way to go in a steam shower. Kerdi membrane is a vapor barrier by itself. But Kerdi membrane over Wedi board is not an efficient use of your monetary resources. Anyone offering that idea? They're not looking out for your best interests. Regular old 1/2" Durock (or equivalent) cement board covered with Kerdi membrane will give you a water and vapor proof system at a fraction of the price (roughly 1/3rd the price) of Kerdi over Wedi. And you can use portland cement based thinsets and grouts. The same with Hydroban. Hydroban by itself is not a vapor barrier. If you use Hydroban in a steam shower you'll need a vapor barrier somewhere else in the wall structure. Hydroban, however, is a fine waterproof membrane for non-steam showers. So for the products you mentioned; Wedi, Kerdi, and Hydroban...for the "best performing" structure with most efficient use of resources, for a steam shower I'd use Kerdi over cement board with portland cement based thinsets and grouts. For a non steam shower I'd use Hydroban over cement board with portland cement based thinsets and grouts. If you really want to use a Kerdi "Board" or Wedi "Board" for the sake of using one of the fancy and expensive "boards", then for the steam shower use Kerdi Board which is water and vapor proof. For the regular shower use Kerdi Board, or use Wedi Board which is only waterproof. If you really want to use epoxies, then have those as well. Epoxies are generally overkill in residential construction. My opinion. In a commercial or in a very often used residential shower or steam shower, they may have benefits. But don't let them up-sell you on those products just because they are the "latest and greatest". They are fine products. They may have their advantages for certain design requirements. But they can also be inefficient, and even a liability, for other design requirements. Realize that the vapor-proof and water-proof comments I made regarding the specific products mentioned are fact. But my recommendations are simply my opinion. I have no aversion to spending more money if required for better construction. But I'm not one to waste money.

A 2/3rds-height toilet wall would contain pretty much all of the water. You could go 3/4 for more protection and a bit more shower privacy. My shower is about the same size and the wall opposite the shower head doesn't see much water up high. Rainheads are a nice for what they are. I have one as a secondary head and we both like it. But as a primary shower head, no I don't recommend them for that. For large showers like yours, I do recommend a handheld somewhere in there with a long hose. Handheld heads offer the same spray strength and patterns as fixed heads. Having one of your heads on a long hose allows you to easily rinse down all corners of the shower when cleaning. Handhelds can be on a sliding bar or on fixed brackets. Consider mounting the shower valve by the shower entry. That way the shower can be turned on without having to step deep into the shower. Depending on where you locate the shower head that is closer to the door? If this will be a doorless entry consider tiling the floor outside the shower entry. The bathroom floor between the shower and the vanity might see some droplets.

Your welcome. Many products come and go in this industry. Products that will be going in the next ten years (my opinion) will be these grouts like Fusion and the foam boards like Kerdi Board. My thoughts. Epoxy grout is not hard to install. Only thing is that you need to clean well. I find a microfiber rag is the best thing to use. Custom Colour: 87.5% Bright White 12.5% Sautrene This is just installed. I set the grout - that took 30 minutes to place it. Then I cleaned the bucket and the grout float. Then I used fresh water and no cleaning agent to do a pre wash. Just the centers of the tiles not the grout joints. Then I cleaned the bucket and set up the initial wash with the cleaning package ad mix. This is when I shape the grout joints and clean up nice. Then you clean the bucket and set up the final wash. You wait an hour for this. After the final wash with the proper ad mix agent I go back right away with the microfibre rag. You feel areas the sponge missed. The micro finer rag leaves the floors flawless. Not a Laticrete spec but something taught to me by a pro. Once you go Microfiberrag - you can not grout the same way ever again. Even with cemenitous grout I do this. I have another grout job this Sunday or Monday. I take a quick video and post it here so you can see what I do. Maybe it changes your mind about Epoxy grout. I used to hate grouting. Hate the unknowns. The random colour changes on and on. Then I tried SpectraLock Pro by Laticrete. Now I can custom make colours and get the same perfect results every time. I just don't use it for steam shower builds. That's it.

Unfortunately, we don't have a plan for the remodel in place yet, because we weren't planning to do it until next year at the earliest. Aside from the window, that bathroom is in decent shape. However, it is a small room and the remodel should be straightforward since we wouldn't be moving any plumbing or changing the layout - just a rip out and replace. The budget is more of a concern, LOL. The other issue is having workers in the house during COVID - this is why we were planning to deal with the exterior trim this summer and wait on any interior work. I ordered a curtain for the window, so hopefully that will buy us some time to figure out what to do. I may just have the exterior carpenter skip that window so we don't waste money, then replace that trim when we are able to do the whole bathroom.