it's just a regular shower drain...

wow

When using a regular floor drain in a steam shower build like this one the transition from the shower to the dry area becomes a concern. You need to factor in capillary action of water wicking and choosing the best materials is key.

You also should know that very few membranes meet the new low perm requirements for high use steam showers. Kerdi DS and NobleSeal TS two of the best options.

I discuss many of these points on my blog pages and have written dozens of ideabooks here on Houzz on the subject.