Does the house already exist? What did your architect recommend?

Ate those windows operable egress windows? Where are the plumbing drains relative to this location? Are the stairs that reach this code legal, or will they need changing? What is the headroom? How was this insulated? Does it meet current electrical code for arc fault?

What else is going to be challenging and costly for this conversion? What type of permitting and inspection process does your city require? Have you hired an architect to plan this and create the permit documents? Done the 200K+ HELOC to finance this? Interviewed reputable contractors to get on their schedule for next winter?

Show the floor below

Are there only two windows on this floor? Is this a townhouse? Will the existing bathroom become part of the master suite? (Will that be acceptable for the user of the office?)

This is a single family new build with optional second floor.  Master is currently on first floor, but we would like to make a second master on this floor.  We are thinking the existing bath will become ensuite.

I’d put closets along the bottom of the floor plan, making a hallway from the stairs to the loft/bedroom area.

Put your linens in "WIC", put a second sink where the closet was in the "Bath 3", hang your clothes in "Bedroom 4", put your bed in "Loft", and forget the gas chamber. I will send you an invoice.

I am assuming that the horizontal blue line is 16'1" and the vertical blue line is 20'0". What are the measurements of the red lines?

A loft generally is open to the lower floor this looks more like a n attic so I need more info and all measurements clearly marked and honestly I do not understand 2 master suites at all. A closet in the office makes no sense . I need to see the style of house too. Maybe a dressing room would work if the house is a bit grand then that "office " sapce becomes a dressing room . I really have no clue what it is you want . Do you hve 2 bathrooms on the mainf floor I think you need to post the whole house floor lan to get real help.

I think you got better starting advice from the 2 nonPROS. The term gas chamber is so disgusting just ugh. Its on their wish list so obviously they want one, as as we debated before, contrary to your opinion, most home owners would like to have one. And Patricia, you offered nothing. If you cant or dont understand a pretty clear question, skip it and come back later. Edit: Also , dont post your entire floor plan (if you are set and ok with your floorplan) if you just want advice for your loft. There are a few people that will tear it apart in sn effort to save you from yourself.

Is it possible to put windows on the other sides (N & S) of the area? Or is this like a gabled attic/second floor where windows can only go on the ends?

Extend Bath 3, remove the closet within it, and use it for added footprint. Steal the WIC from bedroom #4/office for the master.

Having more info about the gable roof and the first floor plan helps to see what space is available and where plumbing can go - it is typically a request made to understand a bigger picture as decisions aren't made in a vacuum. Anyways, here's a scheme based on various assumptions, specifically that there is kneespace under the gable for the closet hanging and the toilet must be against the original wet wall.

One option. If you can add windows on the North wall, I would add one or two in the master bedroom and one in the shower.

EDIT: After reading emilyam819's comment, my layout is pretty much what she said. You could extend the WIC in the master bedroom to the West wall if you are willing to lose the closet in the office.

EDIT2: I would place the toilet on its opposite wall. This way you would have a wall close to the shower to mount a towel bar. You could also have a longer vanity and have a cabinet accessed from the bathroom instead of a closet accessed from the hallway.

Yes, that’s what I meant, suzanne_m. So much better when you draw it!

” it is typically a request made to understand a bigger picture as decisions aren't made in a vacuum.”

I see Patricia ask this on pretty much every post, but I have yet to see her actually do anything with the info. She just throws it out after telling you why SHE hates something.

Assuming that you don't want to move the toilet too far from its current location because of the stack. And also assuming you want to close the bedroom off completely from the stairwell. You could shrink the WIC if it's too large.