This is proposed bathroom renovation. I am overwhelmed. We have changed door to bathroom to a barn type door I want a free standing tub (I use it everyday) I need help in vanities. Finishes. Everything. The rest of the house is a 1940 Dutch colonial with white and black floors and wood floors throughout the rest of the house. Do I need a designer? Gc says he will walk me through everything but I’m afraid I’m going to pick things that just don’t go. My tendency is to just have everything white but it seems super boring. Also. He says I don’t need tile around tub but I think I do. Half wall of subway tile?

Hard to imagine how a walk-in shower "opens up" space when it takes at least as much footprint as the tub, but maybe I'm not understanding the plan. A house needs to have a tub for resale. But it doesn't need one in every bathroom. If taking it out helps your options, go for it! Just remember that 9-year-olds aren't going to reliably squeegee glass or whatever, so keep the upkeep parameters reasonable. Also, if you have a clever way to change the j-and-j into two smaller bathrooms, most people prefer that for many reasons.

Your deflection rating will need to be assessed. Deflection ratings are CHANGED (increased) by adding PLYWOOD. Cement backer board is NOT structural. It is always advisable to use TWO layers of subfloor. The first layer is attached to the JOISTS (the slats you see are the first layer and are considered 'useless' with tile so you might as well get rid of them). The second layer is then screwed to the FIRST layer (do NOT 'screw and glue'). The purpose for TWO layers of subfloor = the top layer is EASILY removed if something changes/goes wrong (glue causes issues with removal = damage to bottom layer = more problems then it is worth). Right. So now you know you need TWO layers of plywood. You can get two layers in there with a total of 1.5" (3/4" + 3/4") worth of 'thickness'. Now you have the RIGHT deflection rating (super important) and you have added quite a bit of height. Now you assess how much extra height you need. A well installed porcelain tile can sit (roughly) 3/4" high. You can add cement board to make up the little bit of difference. There you have it. Two layers of plywood + cement backer board to make up the difference.

You have opened up quite a can of worms with this project! Since the pipes appear to be galvanized iron, I would suggest repiping. That stuff is probably at the end of it's lifespan. Is some of the subfloor nailed in between the joists? I've only seen that once or twice before.