This is a 1.75" tall, 15mm staircase, for the outside of a parapet.
I built it, ready for final spackle coat, in 5 minutes.
Use strips of Foam board, make your staircase.
But wait, Smokey, 3/32" Foam board is too thick, that's more like a 28mm scale stairs!
Settle down! Don't make me call your Probation Officer! I wasn't finished!
NOW, glue on thin strips of Foam sheet, to double the steps!
Fast! Fun! F----- awesome!
I glued on a sheet of Foam on the outside face, cause I need a door under the stairs. Gonna scribe it, then spackle over.