The shingles are just individual pieces of card stock. I added the roof to protect the wheel from heavy snows. A small mill such as this in the upper northeast would typically shut down over the winter when the mill ponds froze over. I added a stove pipe for the pot belly stove used to ward off the chill spring and fall. It has guy wires to keep it steady but you can hardly see them in this photo.
Another neat structure, Bob! There's an old water powered reciprocating sawmill not far away that's an operating museum open in the Spring and Fall. It's closed in the winter not only because the mlll pond freezes, but also because there isn't enough water to run it.
Greg, That's what's next. The mill that I most based this on was an undershot wheel. Mine is an overshot wheel so I must make the sluice that carries water from the pond that's up the grade and delivers it just a bit over the top of the wheel. Gravity does the rest.
Of the three types of water wheel, overshot, undershot, and breast, the overshot is the most efficient but also the most effected by winter temperatures.