Hmmmmmm I have seen pea gravel used for roofing but good rockin material like a golf ball size rock doesn’t seem like it would be on a high rise in NYC.......
Ernest T. Bass Rock Chuckin Society Ping !
I’ve been up on commercial roofs before, that used rock that size for ballast. I want to say it was on thick one-piece rubber membrane type flat roofs, and not on the old-school built-up hot tar and felt flat roofs.