SO2:Stairway

A staircase can be created two ways:

Option1: Create an individual floor block for each step. Each step height increased for each step

Option2:. In the Floor Features, add feature and select the Staircase Preset. All you need is:

Step Count the total number of steps

The dimensions of each tread. This is the width, (Horizontal), and the depth, (Vertical), of the step

Height of each step or total height to define the height of the stairway feature

Note: Make sure that the ceiling has a void, or make an opening with "Anechoic material" to cope with the staircase opening into another room/hallway.