Raised Rafter plate

[Rickt1962]

Even though its all roof on the second level if your are going to have a room up there you need to create a second floor then edit the entire floor go to the dialog setting for entire floor set it to Zero then any walls you draw for the room make sure you use the knee wall settings. Then use your cross section camera and change your design.
Chief really doesnt like Zero's but it works I rather set it to 1.5 inches but you want it on top of the wall .
Remember to set any gables on the walls. , and lock the attic ways that chief creates.