This is the vent from a fairly new furnace (<2yrs). Was showing the buyer and the seller jumped in and said, “that is not a problem, the building inspector looked at it and said it was fine.” I told the buyer, he is right, the AHJ rules, but unfortunately, it does not mean they always know what they approve. It is not safe and needs repair. 13 in. and 16 in. from the corner (which means 20 in. along the pipe).
Bad enough when homeowners screw it up, but then the AHJ goes right along with it. Frustrating.