Start over.......

Show a JPEG drawing of the existing condition of the combined spaces, That means, to scale , every wall, every window and every opening. How are you conditioning the new space? What is the climate?

Show a dotted line for the slant and wall height ...

Nobody can advise anything from what you have posted, and the master bath as posted above? No. Show all to scale with dimensions and include the master bedroom

The pics ar not really helpful . We need a proper floor plan and on that you will add all the measurements and a good showing of ceiling height s everywhere All the rest Jan mentioned . Why agarge attic access from here ? Where do you live is also very helpful. We had an old home where the ceings were sloped and we finally did a dormer space to do a proper bathroom it wass a huge game changer in how that whole attic space functioned .

I am a bit confused here. I think I have pieced together the big 13'x12' room drawing:

• the 2 stand-alone mixing valves in the pictures relate to opposite walls of the old shower in the drawing, now removed but left the mixing valves standing;
• The toilet room and vanity shown in the drawing are existing and still there;
• this 13' x12' bathroom will serve a bedroom, but which one and where?

Can you show more of the house in plan to see how 2 bathrooms will serve 2 bedrooms? Where are the closets? What are your requirements for a Master Ensuite - tub, shower only, toilet room, etc? Also, what Climate Zone are you located and is the roof vented?

The third picture in the post is the existing master bathroom (13' by 12) as it was built and is now. 80% of the space in the master bathroom is wasted. For some reason, the builders located the shower of the master bathroom in the unconditioned space!

The first and second picture in the post is the attic hall. This hall connects to the attic space above the garage. That space is unconditioned. There is no heat there, but we added rockwool insulation. The roof is vented and there are baffles behind the insulation. Climate zone 6.

- Yes to the 2-stand-alone valves for hot and cold water.

- The toilet and vanity are existing and are still there.

In the first and second pictures, you can see the hot and cold valves for the two shower head. I am trying to see if it is possible to put a bathroom in that space to serve Bedroom 3.

The master bathroom already has a vanity and toilet. The only thing we need to add is a shower in the master bathroom. You can see the framing in the third picture. That is the entry to the old shower that is in the unconditioned space.

I have updated the post with additional picture of a plan.

The main issue I see is headroom. Assuming the door into the attic (future bathroom) space is standard height (80"), the outlined area is really the only walkable space there.

The wall separating the attic/bath space from the current master bedroom would have to be moved, it seems to me, to give the new bath enough full-height area. Here's one option that does that--but it also moves the toilet(s), and without knowing what is below this area, I don't know if that could work plumbing-wise.

That lack of headroom in the attic seems daunting. If you took the existing closet for the smaller bedroom, hall closet and the part of the primary closet behind it that could be a bathroom.

Then you could put a reaxh in closet on the end opposite the door for the smaller bedroom. Combining the dressing area and the remaining closet seems like a big enough walk-in for the primary.

hey @mojavemaria, thanks for that idea. Can you please outline it in plan? Thanks!

The fixtures aren't laid out in the proposed new bathroom but we’ve had smaller bathrooms in two houses with no issues.

Your plan looks good on paper but just doesn't seem to match up with your photo of the space IMO. I understand the desire to use ”wasted space” but worry it might make for an uncomfortable to use bathroom.

Thanks @mojavemaria. It is the same existing layout. It might look different because the shower is out. The bathroom always looked big to me, perhaps I am not used to that.

Your primary bathroom is big I'm speaking of the proposed attic bathroom and with that steep slope it looks tight for what you have drawn but you are the one there:)

Thanks @simplynatural. I believe the wall is supporting part of the roof. A small bath with shower (vertical), vanity, and toilet.

I did not draw that, but that should have been reflected in the existing survey. Thanks for that clarification.

@mojavemaria's suggestion to move the wall further into the existing primary bathroom to make enough room for the second bathroom makes the most sense to me in this situation. You simply don't have enough head room in the unconditioned space to make a bathroom that will meet code. You only technically need 5' of width for a standard hall bath but 6' would be more ideal.

Thanks @katinparadise. I will look into this.

A lot of squeeze for no juice. Who took the ORIGINAL bed three bath for closet? I don't understand the "dressing" thing....AT all.

@ janmoyer That was how the builder built the house. This is all original to the build.

Thank you all for your feedback.