Walls below stairs

In this model, there are two sets of stairs. One (consisting of two flights separated by a landing) leading from the basement to the 1st floor. Two: A second set identical to the first leading from the 1st floor to the 2nd floor. The 1st to 2nd floor stairwell is directly above the stairwell to the basement.
Can someone point me in the right direction to create walls that are BENEATH the stairs leading from the 1st to 2nd floor and follow the stairs? I tried increasing the stringer bottom but that simply fills in the small space on the first floor but drastically extends the bottom of the flight to the 2nd floor so that is pokes into the hallway.
The final outcome is one in which the walls follow the stairs, then an interior wall and door leading to the basement stairs. Please see the attached JPG that should give you an idea of the challenge. Thanks, Bill B

Hi Bill,

You can un-check "open" in the stair dialog but I often prefer to just draw the walls to have finer control of the outcome. You have to draw the walls under the stairs (completely under the edge of the stair) to get good clean cuts in the wall.
It depends upon the exact look you want to end up with where the walls are placed relative to the edge of the stair, since I do not know exactly what you are trying to end up with just start with "lined up with the edge of the stair, check the results in camera views. This is probably a great learning opportunity for you to place the walls under the stairs, by the stairs, half-way (centered) on the stair edges and view the differing results until you find just the right look you want.
With the walls directly under the stairs the stair object will cut the wall tops to conform to the angle of the stair rise angle, you will see for yourself the other possible outcomes via experimentation as I suggest.

DJP

David, thank you. I wasn't perfectly clear in my request. I want the walls to follow the zig-zag pattern of the stairs and not follow the straight line of the stair stringer (which you get when you un-check "open"). Is that possible? Bill B. -:)

Figured it out using David's kind comments and the material painter. Sometimes your brain gets in the way of what you are trying to accomplish. Happy Thanksgiving to all. Bill B.