So when being in NZ there is not a lot of option for a lot products in construction unless I want to import. Having products that are available in NZ is far more convenient but sometimes your using them outside there intended application. Is there a way to use a channel drain for a walk-in shower in a bathroom that is intended to be rebated into a concrete floor on a timber floor?

I have a potential design project, in it I have the ability to lower the timber joists as much as I want but is there a way to use a concrete screed on top of a membrane in order to protect the wood but still have the ability to set the drain? would I need another layer of membrane for the tiles that would go on top of the screed? The other factor to account for would be the weight of the screed. I currently have 190x45 joists @ 400 centers but like I said I have a lot of wiggle room in that department. Is it possible or am I missing something else and would the council sign off on it?

thanks for any help in advance.