Here are some pics of my Korber roundhouse with extension. I used some "heavy duty" white cardboard I had lying around and made roof panels that fit. Everything was taped and white glued together. I then made a "roll roofing" from some more masking tape and painted it grimy black.
Surprisingly, it all stayed together for 10 years. It just sat on top of the wooden frames and I removed it many times to detail the interior and access the engines if needed.
Unfortunately, this is all gone as my old layout was demolished for my new one 4 years ago. The old layout was the feature cover story in Run 255. Check it out if you have digital access as it contains a few more pics.
Hope this helps.
Donald
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