Not quite a building but it is scratch built. My version of a Great Lakes ore boat, 8 feet long, 10 inches wide, 20 in. tall to the top of the mast. 99% scratch built except for the windows and doors and stairs. Stairs from a Plasticville coaling station, windows & doors from Lionel bobber cabooses.
I started with a plank of OSB for the keel and 1X's of poplar for the bow and stern. Cabins are foamcore and cardstock. All over layed with 020 styrene from flu shot signs I got from when I worked as a pharmacist.
I put a Suethe smoke unit in the funnel.