Wow! That’s my layout! I’m flattered! The car barn is built on a roughly 2x16 frame of sistered 2x4s. The Floor is open, with hardware cloth and screening to keep bugs out. The roof is vented on one side, and on the other side the roof panels can be removed. I made a set of 8 “rafters” out of OSB, shaped roughly like this:
(http://www.lscdata.com/users/lownote/_forumfiles/rafters.jpg)
On one side both parts of the roof are screwed down, and the space between the two roof panels is open and screened. On the other side the lower roof panel is removable. It’s not screwed into the “rafters,” but fits into a slot at the top. There are screws under the eaves that make it possible to take the roof off. But you can’t pull it off without taking the screws out. This picture kind of explains it–the red arrow points to the little slot the roof fits into. The bit inside the yellow circle represents the part of the roof that extends beyond the wall of the shed. The black arrows represent screws. If you take the screws out, the roof panel just slides down. Takes two people to do it right.
(http://www.lscdata.com/users/lownote/_forumfiles/roofdetail.jpg)
We’re still improving the layout–the car barn is scheduled this weekend to be painted a nice red color. I’m thinking of adding a freight yard…