To my knowledge, no actual plans for the upstairs exist, in fact the ranch house at Lake Tahoe has no second floor.   I have drawn the blueprints from carefully piecing together halls, rooms, windows and doorways from many of the early episodes.   I wasn't always successful and there are some windows on inside walls but I decided the show had a few inconsistencies, so I hope you'll overlook mine.

The captures were taken for the most part to show the rooms.  So although there may be shots of the boys (I couldn't resist), some of them are slightly blurry.

A few notes:

If you'll notice on the show, every person who needed to look out the front window magically had their bedroom there. I've also decided that the Cartwrights' liked to redecorate and swap bedrooms frequently.

For example, in "Vengeance" Joe and Hoss' bedrooms are at the top of the stairs.  But later in "The Pure Truth" Hoss' bedroom has a window where a wall would be if it was the second door at the top of the stairs, like in "Vengeance".  Joe's bedroom in "Dark Star" and "Between Heaven and Earth" has a wall to the right of the entry.  Again, so it can't be at the top of the stairs.

I've added some "mystery rooms" that are needed to support the second floor.  Hop Sing's bedroom must be back there.   Also, Ben mentions the back stairs in the episode "The Saga of Muley Jones," so I have included them here.

Did you notice .....

The master bedroom in "The Saga of Muley Jones" is very similar to Joe's bedroom in "My Brother's Keeper" and a guest bedroom in "A Bullet for a Bride" and Hoss' bedroom in "The Pure Truth".

Adam's bedroom is "The Spitfire" is Joe's bedroom in "Marie, My Love".

 Ben's bedroom in A House Divided had 1970's style beads hanging in the doorway and no door.

The "spanking" bedroom in "Something for Jamie" and The Indian Girl episode ??? was first seen in "The Newcomers" and then redecorated.

Joe's bedroom in "The Truckee Strip" is the dining room in disguise.

So, like I said please try and overlook any inconsistencies.