earthen shower

Hello, I'm brand new here.  This forum keeps popping up when I search for information about waterproofing earthen plasters - so I figured I should join.  I'm building a small studio inside a 120 year old timber barn to live in while I build the longer term strawbale and cob house.  I live in northern california.

I have done several small projects, a couple ovens, small walls, etc and I've taken a couple of workshops but my experience is definitely limited.

I'd like to make the bathroom essentially a wet bathroom or at least a large open shower.  I've never done any waterproof/resistant finishes.  It will also be over a subfloor.  Looking for any tutorials, advice, books that might help.  

seems like Tadelakt is widely recommended for this sort of thing but I'm certainly open to other ideas!  That's just what I keep seeing suggested.  I would like there to be a seamless (or rather bumpless) transition from the bathroom floor to the shower.  I don't think the same level of water resistance would be needed for the entire bathroom as for the shower area so I'm wondering about suggestions for that as well.

Hi Leah,

Welcome to Permies.

Leah, That is an interesting product.
I have not heard of of it before.
I did bit of a looking around.
Tadelakt or Moroccan plaster shares the same lime base as the other surfaces but differs from Venetian plaster and limewash in both finish and durability.
Somewhat laborious to render, Tadelakt plaster requires around seven or eight plaster applications and specialist knowledge to install, but the results are lasting.
How do I make my tadelakt waterproof?
While the Tadelakt still contains moisture an olive soap or a black olive soap (savon noir) is applied and stoned into the surface.
This soaping provides the Tadelakt with its waterproof qualities.

I have never tried an earthen floor on a subfoor.

My main concern would be the mismatch of the expansion of the wood and clay/cob in response to temperature and humidity.
Cob can be sealed with boiled linseed oil which will make it waterproof.

What about linoleum? It should be possible to get a single sheet that covers the whole shower and could be elevated a bit on the edges.

Sebastian, earth is often used as a floor, they are hard work to get established.
It is sealed with linseed oil.
There are a number of topics on this Permies site detailing it.