How would you build a bathroom?

I have a blank slate. The house is 1930s lath and plaster, I want to try my hand at it because it's small. My dream is to have a wet room, with a drain in the middle of the room. Can I sufficiently water proof plaster with the soap and olive oil mix? Does anyone have any experience with this? I was thinking tile flooring. Facebook  <<< video of the demo. The whole floor was rotten.. it's getting a new subfloor tomorrow after replacing the bad wood and getting it leveled.
I am looking into making big handmade tiles at a local studio and also generally keeping my eyes open for a cheap deal on the local market places.  Waddayathink?

A wet room is really smart, especially with limited space.
Might be worth checking your local tile shops. For our last house, we scored several types of really nice clearance tiles. I could not have made them for the prices. (And tile can be hard to make in bulk)
We did the walls in stone tiles ( an auction deal) but did use the bathroom drywall boards behind them. Was still in perfect shape after 15 years when we moved. We used a cast shower base for the bottom but I've seen friends have tiled floors that hold up as well.
There are large tiles being made now that look like marble as well as glass and steel ones.
You never know what you will find at the Habitate for Humanity ReStores. If you have your sizes on hand you may be able to do some cool designs with mixing pieces and tile types.

About what is the number of square feet you're working with?

1930's house may not originally had indoor plumbing.

You mention "level" but in fact if your goal is a wet room I would treat the whole room as if it was a shower stall making sure that it was high at the edges and every bit sloped to the floor drain.

Jay Angler wrote:About what is the number of square feet you're working with?

1930's house may not originally had indoor plumbing.

You mention "level" but in fact if your goal is a wet room I would treat the whole room as if it was a shower stall making sure that it was high at the edges and every bit sloped to the floor drain.

Yes.. the sub floor is the step I am approaching in the coming days,  I certainly will address the sloping carefully. You are correct,  the house has a plumbed addition at the rear. I am pretty sure they added to the front of the house the same time. .The bathroom is 8x5.