Hello, first time posting here.

I am replacing everything in a bathroom, but keeping all the original locations of the tub, toilet, vanity. Attempting to do most of the work myself.

Originally there was a tounge and groove subfloor with a 3/4" press/particle board on top of it. House has a crawl space. I currently have the tounge and groove with 1/2 plywood sanded on one side.

The new floor will be sheet Marmoleum (linoleum) installed professionally. They are also going to install 1/4" plywood to get the floor back to the original height.

What I am trying to figure out is the order and way to put things in.

I have heard to both put the marmoleum under the tub (from Marmoleum, and contratctor that fixed rotten bit of subfloor) and to not put it under the tub (floor installers, and local plumber).

The new tub is a Kohler Devonshire that is acrylic and 20" tall. Per the installation instructions it says to put a 2" bed of mortar. That sounds like a lot, height and weight. Old tub was steel/porcelein about 16" tall.

How do I get 2" of mortar when there was only 3/4 inch thick floor to start with? Build up the floor so it's higher than the hallway by 1 1/4"?

Or put the floor in and put the tup on top of the marmoleum with some sort of border below at the bottom of the apron?

I think the subfloor will need to have support added to do this.

Thank you in advandce for your advice.