Dear colleagues and interested parties, D02 and D04 give an error in the attached project. If the curtain spaces are deleted, there is no problem. Is there a solution without deleting the curtain spaces?[/ quote] Hello, -The floor nets are not formed correctly in the current situation in your project.Make a solution according to the semi-rigid diaphragm method -Item 7.6.9 In the conditions given for the gaps in the curtains, it is said that "...the vertical dimension of the space will not be more than 20% of the floor height". Instead of opening a gap, you can model by inserting beams between 4-5 axis and on the right side of 3 axis.