I’m designing a set of stairs for my new deck, and decided the left hand side of the steps will diminish in size to match the dimension of an existing brick walkway. The overall reduction, to be achieved with three steps is 16". Simple arithmetic says each step needs to be ~ 5 5/16+ smaller than the preceding one to reach the 16" reduction total. To see what this would mean visually, I took the model of the stairs, and drew a line from the first full size step corner to the corresponding corner on the bottom, or final step, and then dimensioned the resulting intersections with the line and each step. The results surprised me.

I must be missing something in the 3-D, but I can’t figure it out. Pier Stairs Size Reduction Plan.skp (255.5 KB)