I hate to say it, but given the space constraints, this is a bad idea! If you are following the proper path and obtaining permits for the new bathroom, I do not know an inspector who will pass that space due to code requirements. If you're main goal is to get a walk-in shower, consider merging the two bathrooms and creating one fantastic space, possibly with a second door leading in from the master bedroom.

Just a quick scetch, not knowing what your hallway looks like and such. When moving the doorway to the other bathroom, you could use that corner for a shower.

Thanks so much @rinqreation for thinking outside the box! It's a great idea & I may just do something like that - the plan I provided was not accurate re the stairs - they actually end as attached so I cannot move the wall further south - I can however move the doorway over to accommodate a wider shower.

I was hoping not to do that as I need the wall for a vanity or linen cabinet as the toilet may need to be put on the east wall because of my floor joists - it's long and convoluted but I really appreciate your suggestion & sorry about my previous drawing.

I do have a permit by the way.

You are brilliant!! I'll take a look & see if we can sacrifice more space in the bedroom - thank you so much!

Your existing space does not have enough room for three fixtures. You need to get some guidance on minimum clearances. There are specific requirements for size of shower, both total floor space and minimum dimension and also for the unobstructed width of the entry. There are also numbers for distance from centerline of a fixture to the adjacent item and clear floor space required in front of a fixture. If you are dealing with an upstairs bath with slanting walls, there are headroom requirements to consider as well.

Given the dimension above, your space would require that the toilet run lengthwise and you could have a second fixture at the opposite end of the room but even that would require close attention to sizes and clearance details. You could put the toilet and shower in that space and have the lavatory on the outside wall of the bathroom in the bedroom itself.

We just got finished renovating our ensuite. We took 2' 4" from our bedroom. We don' miss the space we took from the bedroom and the bathroom turned out just great. Try that option.

Thanks @nancyann0277a - it looks like a viable option for sure - it's funny how I tried to think of so many other options but never what seems like the easiest.

I agree with Linda, look up minimum clearances and work accordingly.

And the toilet drain is often the hardest to place, but it won't matter if you turn the pot, for example.