I wrapped up the scratch build today, the hardest part of it was finding an image to turn into an interior. Fortunately, the St. Louis NMRA has a lot of free downloads. http://www.gatewaynmra.org/2002/easy-industrial-building-interiors/
The roof is made out of cardstock and shipping labels. I printed a Clever Models tar paper texture on to a 8×11 label and cut to fit.