Hello friends, I'm drawing a project with 80cm basement curtain and I created a staircase, the problem is that now I created the basement not separately, but combined with the ground quota, and I can't put any filling in that 80 cm gap, neither the floor seems to be a gap, and when I create the stairs, the 80cm lower gap starts from the floor, I How can I fill that gap? below the basement level 0, the end of the basement +0.80 floor 1st floor level +3.65 I am waiting for your help