Most people can recite what A40, A60 and G90 mean. Far fewer can explain why the standard governing steel doors steers you away from the coating with the most zinc on it. Here is what the letter and the number actually tell you, and which one belongs on a painted hollow metal door.
Commercial door hinge sizes are the smallest line on a hardware schedule and one of the most expensive to get wrong. A hinge that a half-inch short, a grade too light, or two-to-a-leaf on a door that needed three doesn’t fail on install day. It fails eighteen months later, when the top hinge has pulled, the leaf has dropped, and the door drags the frame every time someone opens it. By then its a callback, not a line item
“Standard hollow metal door sizes, the nominal-vs-actual undercut that trips up orders, and how to size a rough opening correctly.”
“Wood vs. Hollow Metal: “Neither door is better — each is better at something. A commercial buyer’s honest guide to speccing wood vs. hollow metal opening by opening.”