To create a mezzanine, first add a floor. To find out how to create a floor, click here.
Position yourself on your floor. Then go to the menu and click on Build > Staircases > Straight (or spiral) staircases > Floor opening.
Draw the limit of your mezzanine.
Note: the floor opening can be placed on the wrong side of your floor.
Here we want the floor opening and the room to be reversed.
You can modify the settings of the areas. Click on Floor opening and then on the Properties icon. Go to Type and select the type of room your mezzanine should be. Here we will choose Bedroom. Then click on Room > Properties. Go to Type and select Floor opening at the end of the drop-down menu.
This will reverse the floor opening and the room.
Tip: to add a handrail, click on a floor opening limit to access the Properties. Select Handrails.
Please note, it is not possible to create a mezzanine in the roofing.