Hi Ashot, I have no issue setting my building and site model to the correct z elevation. As you can see, I have a layer set to zero for my site model and all subsequent layers are for the two building on the site. If, you place section line on the same layer you are sectioning. It will reside on that layer and not 0.0 (Z). For instance if I want to section building E level 1, I would draw the Section line on Design Layer "Level 1 D+E". That section line or any other planar Object be created on that layered not and not 0.0 (Z). I, think this works because 2D objects considers all design layers 0.0 even though the actual elevation could be 997.2083. I hope this helps
The site model is on the "site" layer