How I built my HO scale roundhouse roof

I've had a scratchbuilt roundhouse for my PRR operations for many years now, but it's always had a perfectly flat roof. Originally, I built it with a sloped roof, but it never looked right, so I went back to a flat roof many eons ago. I always wanted to do something to jazz up the overall profile, but wasn't sure what to do until now.
After studying some roundhouse pictures, I saw it was pretty common to half a "half roof" of windows that arced around the entire building. I decided that was something I could do for mine to make it look a lot nicer.

Here's how I built my roundhouse roof.

Using the existing roof as a template, I then marked off a new "arc" that was half as deep on 1-inch thick insulation foam. Here, you can see the original roof, the template (left) for the new addition and the arc traced onto the foam, ready for cutting. The new arc is black foam core and will serve as the top layer of my roof.

Test fitting to make sure I have all the measurements right and that it will look good.

Gluing the foamcore to the insulation foam after painting the foam a color close to the original roundhouse color.

I stole windows from two Walthers Champion Meat Packing kits because they were the perfect size for this project. I also installed many small vents for some visual interest. (The clamps are back on because that particular corner pulled up a bit and I had to reglue.)

I just glued the windows directly to the surface of the foam. Close up, it looks so-so, but in place, you don't notice the windows are jutting out.

The completed roof in place. Much better! The old roof was just the lower layer. And yes, it's still removable. The upper portion is glued to the lower, so it lifts off in one large section and is very light.

Another angle. This photo gives the building a bit of bulge that isn't there. I added DPM supports to match the lower level to make it blend in. You'll notice the colors is a bit off as I wasn't able to match it perfectly. I've since made some further refinements to the color and added more weathering to blend it all in.

A view from above. Overall, a simple project that really added to the look of the roundhouse.