Part 2: Building the box.
To assemble the structure, I first assemble a wall and an end to form an L, and do likewise with the other wall and end. Then after these are dry, I glue the 2 "Ls" together to get the box. You can see the stripwood bracing on the inside. Then I cut and added a ridgepole.
Here are the doors. Originally I was going to make them hinged, but then I decided to make them rolling doors along an upper track. Anyway, note how the trim on the left side of the door is cut away to get a tighter fit against the wall of the structure. This isn't 100% prototypical, but will look better from the viewing angle for the structure as a whole.
I did the foundation by building a 3-sided box with mitred corners from stripwood, then sanding and painting the wood to seal. Then I painted stonework onto that foundation. Here's a test-fit to make sure the loco fits!
Finally, I built the cupola (that was actually the hardest part). Here's the completed structure on-location (ignore that 12penny nail stuck in the styrofoam, this is trimmed from a larger photo.
I still need to weather the roof (with chalks).
Anyway, that's a quick primer on how I scratchbuilt this, in 2 postings and 8 photos