Strap Hanger - The total materials used for the kit-bash was the Bachmann Union Station - #45976, white foam core, thin balsa, square styrene stock and card stock. and of course paint, adhesives and pastel chalk. The skylight comes with the building. It was meant to be the entire roof of the station. I cut out its plastic windows, to allow light to get through. I made a 1/2 frame out of foam core to raise the skylight above the foam core roof (there is a hole in the roof the frame sets in). I used the balsa to trim out the top of the foam core and the styrene for a ledge to support the roof. The original sides of the building were glued to the front. Foam core makes up the sides and back wall where it meets the kit back wall.
I meant to leave the skylight green, but accidentally spray painted it white in a DOH moment or "what was I thinking" moment - some call it a senior moment. Anyway I like the way it turned out. I used silicone caulk adhesive to glue the roof to the building and the skylight to the foam core. I had a hard time having the more common adhesives bond plastic to foam core. I did use a gorilla urethane glue to mate the back wall together. Could have used the silicon there as well.
This is a short building just a hair over 4 inches or 16 scale feet tall so at best a single story train station.
Long answer to a short question Jeff