I took an architecture history course in Quebec. The professor put up some slides of pueblos in the Southwestern United States, mud brick buildings with flat roofs. One student raised her hand and asked, “How do the roofs shed the snow?”
I was reminded of that because I’ve been puzzling over the roofs of castles. The structures with crenelations have roofs that do not extend over the walls. I’ve been wondering how they shed the rain.