Forestshepherd

I'm currently drawing plans for a pole barn that is being converted into a "barndominium". I have the roof mostly drawn but I can't figure out how to draw purlins on chief architect x12. There is a video out there already explaining how to add purlins, but the program used in the video is older and doesn't have the same prompts as x12. Attached are a photo of the roof purlins and a screenshot of what I have drawn up so far.

I have checked every wall on my structure and none of them have "No Room Definition" selected. All of my walls seem to be completely enclosed. My Room Layer Display is unlocked. Is there something else I should look into? As you can see in the screenshot, whenever I try to select a room, the Slab Specification window pops up. I am unable to select a room in any part of my structure. Hoping there is a simple fix for this! Thanks so much for any help you can offer!