Rustic staircase can be placed anywhere in the room. Place the top part on the upper floor to cutout the floor.
Requires Ravasheen Uplifting Elevator Mod, linked in the required tab.

Make sure your game is fully updated.

I have installed packs:

Expansion Pack
Get To Work
Get Together
City Living
Cats and Dogs
Seasons
Get Famous
Island Living
Eco Lifestyle
Discover University
Cottage Living
Snowy Escape
High School Years

Game Pack
Outdoor Retreat
Spa Day
Dine Out
Vampires
Parenthood
Jungle Adventure
Strangerville
Dream Home Decorator
My Wedding Stories
Werewolves

Stuff Pack
Luxury Party
Perfect Patio
Cool Kitchen
Romantic Garden
Kids Room
Moschino
Tiny Living
Spooky
Laundry Day

Industrial Loft Kit
Blooming Rooms Kit

Free:
Holiday Celebration Stuff
Grim's Ghoulish Guitar


Cheats I've used:
debug
bb.moveobjects

To install this room into your game:
- download the room
- unzip room files
- copy room files and paste them into your Tray catalog ([...]My Documents/Electronic Arts/The Sims 4/Tray]
- all CC - objects from --> Required Tab go to the Mods folder.

CC's needed for this Room - Please read in the Required Tab.

Credits: All TSR CC's Creators